Solvent free resorbable resin for 3D printing

Abstract

In various embodiments, the present invention provides a solvent free 3D printable resin comprising a linear or star-shaped poly(allyl glycidyl ether succinate) ("PAGES") copolymer, and a multi-functional thiol crosslinker, as set forth above. In one or more of these embodiments, the poly(allyl glycidyl ether succinate) ("PAGES") copolymer will be a linear copolymer formed by ring opening copolymerization of allyl glycidyl ether and succinic anhydride, initiated by a mono-or bi- functional initiating alcohol and using a 2,6-di-tert-butyl-4-methylphenoxide (Mg(BHT)2(THF)2) catalyst. These resins may also include at least one suitable photoinitiator and, optionally, a light attenuating agent or photoinhibitor. Advantageously, it has been reported that these resins have a complex viscosity that is suitable for 3D printing (from about 0.5 Pa·s to about 20.0 Pa·s) at room temperature without the need for a solvent or other diluent.

Description

SOLVENT FREE RESORBABLE RESIN FOR 3D PRINTINGSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DE VELOPMENT SUPPORT

[0001] This invention was made with government support under Grant 1R01HL 159954-01 Al awarded by the National Heart Lung and Blood Institute (NHLBI) at the National Institutes of Health (NIH). The government has certain rights in the invention.CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U. S. provisional patent application serial number63 / 544,353 entitled “Solvent Free Resorbable Resin for 3D Printing,” filed October 16, 2023, and incorporated herein by reference in its entirety.FIELD OF THE INVENTION

[0003] One or more embodiments of the present invention relates to a resorbable resin for 3D printing resin. In certain embodiments, a solvent free resorbable resin for use in 3D printing applications.BACKGROUND OF THE INVENTION

[0004] Advancements in additive manufacturing techniques are enabling the development of patient specific scaffolds and devices. However, these advances will be highly dependent on the availability of printable materials that meet the chemical, mechanical, and biological requirements of the specifi c application. Various forms of additive manufacturing, more colloquially known as 3D printing, have been demonstrated in the literature. Some such forms of additive manufacturing involve vat polymerization. Vat photopolymerization utilizes UV light to selectively cure liquid, polymeric resins into solid, 3D printed parts. The two most prominent types of vat photopolymerization include stereolithography, which cures resins in a point-by-point fashion using a laser, and digital light processing (DLP), which cures resins in a layer-by-layer fashion using cross-sectional projections of UV light. DLP printing is widely used for academic research because it is economical, efficient, and capable of high spatiotemporal resolution printing.

[0005] While there are many advantages associated with DLP printing, there are also limitations to the technology. While variations of DLP have been created to exploit resins with a wide range of viscosities, traditional and commercially available versions of this technology generally require the use of low viscosity resins (< 10 Pa.s or 10,000 cP) for multiple reasons. (See, e.g., Weng, Z. et al . “3D Printing of Ultra-High Viscosity Resin by a Linear Scan-Based Vat Photopolymerization System.” Nat Commun 2023, 14 (1), 4303; Bao, Y.; Paunovic, N.; Leroux, J.-C. Challenges and Opportunities in 3D Printing of Biodegradable Medical Devices by Emerging Photopolymerization Techniques. Advanced Functional Materials 2022, 32 (15), 2109864; Luo, Y.; Le Fer, G; Dean, D.; Becker, M. L. 3D Printing of Poly(Propylene Fumarate) Oligomers: Evaluation of Resin Viscosity, Printing Characteristics and Mechanical Properties. Biomacromolecules 2019, 20 (4), 1699—1708, the disclosures of which are incorporated herein by reference in their entirety). First, resins must readily flow between the build plate and the resin vat to refill the void space that occurs after each layer is cured. (See, e.g., Tumbleston, J. R. et al. “Continuous Liquid Interface Production of 3D Objects.” Science 2015, 347 (6228), 1349-1352, the disclosure of which is incorporated herein by reference in its entirety). Second, lower viscosity resins are less likely to cause part, delamination due to suction forces generated when the build plate moves upward. (See, e.g., Shin, Y.; Becker, M. L. “Gradient versus End-Capped Degradable Polymer Sequence Variations Result in Stiff to Elastic Photochemically 3D-Printed Substrates.” Biomacromolecules 2022, 23 (5), 2106—2115, the disclosure of which is incorporated herein by reference in its entirety). Third, lower viscosity resins generally exhibit high isotropy and good dimensional accuracy. See, e.g., Mason, K. S., et al. “3D-Printed Porous Supramolecular Sorbents for Cobalt Recycling.” J. Am. Chem. Soc. 2024, 146 (6), 4078-4086, the disclosure of which is incorporated herein by reference in its entirety).

[0006] One commonly used method to decrease a resin viscosity for 3D printing is the incorporation of a solvent or reactive diluent into the resin. For example, diethyl fumarate (DEF) has been extensively reported as a reactive diluent used to DLP 3D print polypropylene fumarate). (See, e.g., Le Fer, G.; Becker, M. L. 4D Printing of Resorbable Complex Shape-Memory Polypropylene Fumarate) Star Scaffolds. ACS Appl. Mater. Interfaces 2020, 12 (20), 22444- 22452, the disclosure of which is incorporated herein by reference in its entirety)- However, there are disadvantages associated with both reactive diluents and solvents. Reactive diluents limit control over network crosslinking and thus mechanical properties of the resulting printed partbecause an excess of crosslinker must be present to sufficiently reduce resin viscosity. (See, e.g., Shin, Y.; Becker, M. L. “Gradient versus End-Capped Degradable Polymer Sequence Variations Result in Stiff to Elastic Photochemically 3D-Printed Substrates.” Biomacromolecules 2022, 23 (5), 2106-2115, the disclosure of which is incorporated herein by reference in its entirety). Incorporation of excessive amounts of solvent in resin formulations can cause significant, nonuniform 3D printed part shrinkage resulting in inhomogeneous residual stress formation, cracking, and warping throughout printed parts. (See, e.g., Barker, C. M., et al. “Solvent-Free Vat Photopolymerization of Unsaturated Polyesters: Structure-Property Relationships for Depolymerization.” MRS Communications 2023, 13 (5), 841-847. and Zhang, Q.et al. “Design for the Reduction of Volume Shrinkage-Induced Distortion in Digital Light Processing 3D Printing.” Extreme Mechanics Leiters 2021, 48, 101403, the disclosures of which are incorporated herein by reference in their entirety). Previously reported DLP systems used to print polypropylene fumarate) have been shown to require 30-40 wt.% of solvent to reduce their resin viscosity to below printable limits. (See, e.g., Shin, Y.; Becker, M. L. “Gradient versus End-Capped Degradable Polymer Sequence Variations Result in Stiff to Elastic Photochemically 3D-Printed Substrates.” Biomacromolecules 2022, 23 (5), 2106-2115 and Kirillova, A.; Yeazel, T. R.; Gall, K.; Becker, M. L. “Thiol-Based Three-Dimensional Printing of Fully Degradable Poly(Propylene Fumarate) Star Polymers.” ACS Appl. Mater. Interfaces 2022, acsami.2c06553, the disclosures of which are incorporated herein by reference in their entirety).

[0007] Moreover, it is believed that patient specific devices will require highly specialized polymers that can be easily functionalized and tuned widely for both mechanical and degradation properties. Polyesters such as poly(ε-caprolactone) (PCL), poly(L-lactic acid) (PLLA), and polypropylene fumarate) (PPF) have all been investigated as tissue engineering scaffolds, but each requires tuning of thermal, mechanical, rheological, and degradation properties before they can be used widely for regenerative medicine. Moreover, to be used to produce 3D scaffolds that are compatible with biological systems, the polymer should be non-toxic, implantable without rejection, and completely resorbable upon degradation. While the first two criteria are achieved in a multitude of polymer systems, there are relatively few examples that are also bioresorbable: polylactides, poly(ε-caprolactone) (PCL), and polypropylene fumarate) (PPF).

[0008] Each of these examples are polyesters and thus, able to degrade either enzymatically or through hydrolysis in vivo. However, as a consequence of the rapid degradation of PLLA,acidosis and inflammation of the surrounding tissue area are regularly observed. Conversely, the slow degradation of PCL in the human body limits its use in tissue repair, particularly with regards to reforming vascular tissue. Further, whi le both PLLA and PCL can be extruded through FDM to produce 3D scaffolds capable of undergoing in vitro degradation, these materials exhibit only moderate mechanical and tensile properties, with the majority of defects in the material are observed at the interface between deposited layers. Additionally, as a consequence of the achievable width of the extrusion nozzle in FDM, the resolution of the 3D printed scaffolds made using these polymers is limited.

[0009] PPF is an unsaturated polyester that can be formed by the ring-opening (co)polymerization (ROCOP) of maleic anhydride (MAn) and propylene oxide (PO). It has been previously reported to produce the PPF cis-alkene isomer polypropylene maleate) (PPM), which can be isomerized into PPF using a weak base at low (60 °C) temperatures. Advantageously, ROCOP allows for a high degree of control over the molecular mass distribution and end-group fidelity through the variance of the ratio of monomer(s) to alcohol initiator. Recent studies of PPF synthesis via ROP, including contact cytotoxicity assays and cell culture results, have shown that PPF polymers produced by ROP are non-toxic and that cells attached and proliferated well on its thin films. Furthermore, PPF degrades in vivo to form fumaric acid and propylene glycol, which are excreted, and generally does not cause the acidosis and inflammation of the surrounding tissue area that is regularly observed with PLLA.

[0010] Unfortunately, however, high molar mass PPF polymers (>5000 Da) are not liquids at room temperature and in order to enable their use in printable PPF resins they must be diluted into the reactive diluent diethyl fumarate (DEF), which acts as both solvent and crosslinking agent. These resins have been studied and shown to be able to produce 3D scaffolds with compressive moduli comparable to bone. A major drawback to the use of PPF polymers in these systems is that any excess DEF (i.e. any DEF not actually crosslinking the PPF polymer chains) must be removed before the printed structure can be used in biological systems. Even in cases where a crosslinker other than DEF (e.g., and multifunctional thiol crosslinker) is used in these PPF resins, a diluent like DEF is still necessary to obtain a viscosity suitable for 3D printing. Unfortunately, removal of this diluent / solvent creates shrinkage in the printed polymer construct, typically adding residual stress to the printed construct.

[0011] An alternative approach to diluting polymere with solvent to achieve printable viscosities could be to design a polymer with an inherently low viscosity. For example, comb polymers, a class of linear polymer with low density side chains, are widely known for their interesting rheological properties. (See, e.g., Abbasi, M.; Faust, L.; Wilhelm, M. “Comb and Bottlebrush Polymers with Superior Rheological and Mechanical Properties.” Advanced Materials 2019, 31 (26), 1806484, the disclosure of which is incorporated herein by reference in its entirety). As the number of non-entangling side chains on a comb polymer increases, the relaxation time of the polymer decreases, thus the viscosity of the polymer decreases. (See, e.g., Abbasi, M.; Faust, L; Wilhelm, M. “Comb and Bottlebrush Polymers with Superior Rheological and Mechanical Properties.” Advanced Materials 2019, 31 (26), 1806484, the disclosure of which is incorporated herein by reference in its entirety). This relationship highlights comb architectures as interesting for low viscosity applications. Recent investigations into processing methods of comb polymers have shown their potential in various types of 3D printing such as extrusion and DLP systems. See, e.g., Choi, C., et al. Digital Light Processing of Dynamic Bottlebrush Materials. Advanced Functional Materials 2022, 32 (25), 2200883, the disclosure of which is incorporated herein by reference in its entirety).

[0012] Thus, what is needed in the art is a degradable, solvent free 3D printable resin that has a complex viscosity that is suitable 3D printing at room temperature (from about 0.5 Pa.s to about 20 Pa.s) without the need for a solvent or other diluent.SUMMARY OF THE INVENTION

[0013] In various embodiments, the present invention provides a solvent free 3D printable resin comprising a poly(allyl glycidyl ether succinate) (“PAGES’’) copolymer, and a multi-functional thiol crosslinker. In one or more of these embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) copolymer is a low viscosity, degradable polyester formed by ring opening copolymerization of allyl glycidyl ether and succinic anhydride, initiated by a mono-, bi- or multi- functional initiating alcohol and using a 2,6-di -tert-butyl-4-methylphenoxide (Mg(BHT)2(THF)2) catalyst. The architecture of PAGES was inspired by a comb polymer architecture with side chains that do not entangle, contributing to lower viscosity under ambient conditions. Stochiometric control over PAGES polymerization allows for targeted degree of polymerization (DPn) and viscosity values while also enabling large-scale synthesis approaching Kg scale, even in anacademic laboratory. PAGES copolymers exhibits a direct correlation between oligomer molecular mass and degree of crosslinking with mechanical properties and degradation profile, which allows for prospective design of materials.

[0014] When used in combination with degradable thiol crosslinkers, these PAGES copolymers afford a solvent free DLP 3D printing system . That is, these PAGES copolymers can be 3D printed without the need to incorporate a solvent or reactive diluent into the resin. In some embodiments, these resins will further comprise at least one suitable photoinitiator, such as phenylbis(2,4,6- trimethylbenzoyl)phosphine oxide (BAPO) and a light attenuating agent or photoinhibitor, such as oxybenzone or 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO). Advantageously, it has been found that these resins have a complex viscosity that is suitable 3D printing (from about 0.5 Pa.s to about 20 Pa.s) without the need for a solvent or other diluent. Moreover, because they have no solvent, these resins avoid the problems with shrinkage and the attendant increase in stress to the polymer printed structure that ordinarily happens when the residual solvent is removed. Varying resin formulations of P AGES polymer are shown to decrease part shrinkage from 14% to 0.3%. 3D printed parts fabricated from PAGES possess tensile modulus values between 0.43 and 6.18 MPa and degradation profiles are shown to vary between 12 and 40 days under accelerated conditions based on polymer degree of polymerization and crosslink ratio.

[0015] In a first aspect, the present invention is directed to a solvent-free resin for 3D printing comprising: a linear poly(allyl glycidyl ether succinate) copolymer having a degree of polymerization of from about 2 to about 20; and a multi-functional thiol crosslinker: wherein said solvent free resin has a complex viscosity of from about 0.5 Pa.s to about 20.0 Pa.s. In some embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the poly(allyl glycidyl ether succinate) copolymer comprises the ring opening copolymerization reaction product of succinic anhydride and allyl glycidyl ether using a mono- or bi-functional alcohol initiator and Mg(BHT)2(THF)2 catalyst.

[0016] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or m ore of the above referenced embodiments of the first aspect of the present invention, wherein the shaped poly (allyl glycidyl ether succinate) copolymer comprises a linear copolymer having two poly(allyl glycidyl ether succinate) chains emanating from a residue of a bi-functional alcohol initiator.

[0017] In some other embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the linear poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having the formula:where R is a residue of a mono-functional initiating alcohol and x is an integer from 2 to 20.

[0018] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the linear poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having the formula:where a is an integer from 2 to 20 and x is an integer from about 2 to about 20.

[0019] In some of these embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having a formula selected from:where x is an integer from about 2 to about 20.

[0020] In one or more embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) polymer used to form the solvent-free PAGES resins will be a linear copolymer having a neat viscosity near or below 15 Pa.s. In some embodiments, the poly(allyl glycidyl ether succinate)(“PAGES”) polymer used to form the solvent-free PAGES resins will be a linear copolymer having a neat viscosity near or below 12 Pa.s, in other embodiments, near or below 11 Pa.s, in other embodiments, near or below 10 Pa.s, in other embodiments, near or below 9 Pa.s, in other embodiments, near or below 8 Pa.s, in other embodiments, near or below 7 Pa.s, in other embodiments, near or below 6 Pa.s, in other embodiments, near or below 5 Pa.s, in other embodiments, near or below 4 Pa.s, and in other embodiments, near or below 3 Pa.s.

[0021] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the poly(allyl glycidyl ether succinate) copolymer has a degree of polymerization of from about 5 to about 20.

[0022] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the multi-functional thiol crosslinker has from 2 to 4 thiol functional groups. In various embodiments, the solvent-free resins for 3D printing of the present inventi on include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the multi-functional thiol crosslinker is selected from the group consisting of trimethylolpropane tris (3 -mercaptopropionate), bis(3-mercaptopropyl) succinate, pentaerythritol tetrakis(3-mercaptopropionate), isosorbide bis(3 -mercaptopropionate), 2,2’-((diisopropylsilanediyl)bis(oxy))bis(ethane-l -thiol) and combinations thereof. In some of these embodiments, the solvent-free resins for 3D printing of the present invention include any one or m ore of the above referenced embodiments of the first aspect of the present invention, wherein the multi-functional thiol crosslinker has the formula:

[0023] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the multi-functional thiol crosslinker comprises from about 0.1 to about 10.0 mole percent of said solvent-free resin. In one or more embodiments, the solvent-free resinsfor 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the multi-functional thiol crosslinker comprises about 0.1 to 10 mole percent of said solvent-free resin. In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the multi-functional thiol crosslinker comprises from about 1 weight percent to about 36 weight percent of said solvent-free resin. In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the multi-functional thiol crosslinker comprises from about 8 weight percent to about 12 weight percent of said solvent-free resin.

[0024] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, comprising about 99 wt.% or more of said poly(allyl glycidyl ether succinate) copolymer.

[0025] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein a molar ratio of allyl groups on said pol y(allyl glycidyl ether succinate) copolymer to thiol groups on said multi-functional thiol crosslinker is from about 2:1 to about 20:1. In one or more of these embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, wherein the molar ratio of allyl groups on said poly(allyl glycidyl ether succinate) copolymer to thiol groups on said multi-functional thiol crosslinker is about 5:1.

[0026] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, containing 2.0 wt.% or less, preferably 1.0 wt.% or less, and more preferably 0.1 wt.% or less, of a solvent or diluent.

[0027] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or m ore of the above referen ced embodiments of the first aspect of the present invention, further comprising at least one photoinitiator. In some of these embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of theabove referenced embodiments of the first aspect of the present invention, wherein the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO).

[0028] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the presen t inven tion, further comprising a light attenuating agent. In some of these embodiments, the light attenuating agent is oxybenzone. In some embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, further comprising BAPO and oxybenzone. In some embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention further comprising 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO).

[0029] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, having a degradation temperature (Td) of from about 250 °C to about 310 °C. (probably not needed) In various embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, having a glass transition temperature (Tg) of from about -50 °C to about -10 °C. In some embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, having a complex viscosity of from about 0.5 Pa.s to about 10 Pa.s.

[0030] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention comprising: from about 80 wt.% to about 99 wt.% of said poly(allyl glycidyl ether succinate) copolymer; from to 0.1 mol.% to about 10 mol.% of said multi-functional thiol crosslinker, wherein the molar ratio of allyl groups in said poly(allyl glycidyl ether succinate) copolymer to thiol groups in said multi-functional thiol crosslinker is from about 2:1 to about 20: 1 ; and from about 0.1 wt.% to about 3 wt.% of a photoinitiator. In some embodiments, the solvent- free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention comprising: from about 80 wt.% to about 99 wt.% of said poly(allyl glycidyl ether succinate) copolymer; from to 1 wt.% to about 20 wt.% of said multi-functional thiol crosslinker, wherein the molar ratio of allyl groups in said poly(allylglycidyl ether succinate) copolymer to thiol groups in said multi-functional thiol crosslinker is from about 1 : 1 to about 20: 1 ; and from about 0.1 wt.% to about 3 wt.% of a photoinitiator, hi some embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention, further comprising from about 0. 1 wt.% to about 3 wt.% light attenuating agents or photoinhibitors.

[0031] In one or more embodiments, the solvent-free resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the first aspect of the present invention wherein the multi-functional thiol crosslinker is trimethylolpropane tris (3- mercaptopropionate) and the poly(allyl glycidyl ether succinate) copolymer has a formula selected from:

[0032] In a second aspect, the present invention is directed to a low solvent resin for 3D printing comprising: a linear or poly(allyl glycidyl ether succinate) copolymer having a degree of polymerization of from about 5 to about 50; a quantity of a solvent or reactive diluent, wherein said solvent or reactive diluent comprises less than 1 wt.% of said low solvent resin; and a multi- functional thiol crosslinker; wherein said low solvent resin has a complex viscosity of from about 0.5 Pa.s to about 20.0 Pa.s. In carious embodiments, the low solvent resins for 3D printing of the present invention further comprising at least one photoinitiator.

[0033] In one or more embodiments, the low solvent resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the second aspect of the present invention, comprising about 80 wt.% of said poly(allyl glycidyl ether succinate) copolymer. In some embodiments, the low sol vent resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the second aspect of the present invention, comprising a star shaped poly (allyl glycidyl ether succinate) copolymer. In one or more embodiments, the low solvent resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the second aspect of the present invention, wherein the multi-functional thiol crosslinker has from 2 to 4 thiol functional groups.

[0034] In one or more embodiments, the low solvent resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the second aspect of the present invention, wherein the multi-functional thiol crosslinker has the formula:

[0035] In one or more embodiments, the low solvent resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the second aspect of the present invention, wherein the multi-functional thiol crosslinker comprises from about 0. 1 to about 10.0 mole percent of said solvent-free resin. In some embodiments, the low solvent resins for 3D printing of the present invention include any one or more of the above referenced embodiments of the second aspect of the present invention comprising from about 80 wt.% to about 98 wt.% of said low solvent resin.

[0036] In a third aspect, the present invention is directed to a 3D printed polymer structure formed from the solvent-free resin described above.

[0037] In a fourth aspect, the present invention is directed to a 3D printed polymer structure formed from the low solvent resin of described above.

[0038] In a fifth aspect, the present invention is directed to a linear poly(allyl glycidyl ether succinate) copolymer for use in 3D printing comprising two poly(allyl glycidyl ether succinate) copolymer segments each having a degree of polymerization of from about 5 to about 100 wherein said two poly(allyl glycidyl ether succinate) copolymer segments are joined to each other through the residue of a bi- functional alcohol initiator. In some of these embodiments, the linear poly(allyl glycidyl ether succinate) copolymer comprises the ring opening copolymerization reaction product of succinic anhydride and allyl glycidyl ether using a bi-functional alcohol initiator and Mg(BHT)2(THF)2catalyst.

[0039] In one or more embodiments, the linear poly(allyl glycidyl ether succinate) copolymers for use in 3D printing of the present invention include any one or more of the above referenced embodiments of the fifth aspect of the present invention, wherein the linear poly(allyl glycidyl ether succinate) copolymer comprises two poly(allyl glycidyl ether succinate) chains emanating from a residue of a bi-functional alcohol initiator. In some embodiments, the linear poly(allyl glycidyl ether succinate) copolymers for use in 3D printing of the present invention include any one or more of the above referenced embodiments of the fifth aspect of the present invention, wherein the linear poly (allyl glycidyl ether succinate) copolymer comprises a poly (allyl glycidyl ether succinate) chain emanating from a residue of a mono-functional alcohol initiator.

[0040] In one or more embodiments, the linear poly(allyl glycidyl ether succinate) copolymers for use in 3D printing of the present invention include any one or more of the abovereferenced embodiments of the fifth aspect of the present invention, wherein the linear poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having the formula:where a is an integer from 2 to 20 and each x is an integer from about 2 to about 50. In some of these embodiments, the linear poly(allyl glycidyl ether succinate) copolymers for use in 3D printing of the present invention include any one or more of the above referenced embodiments of the fifth aspect of the present invention, wherein the linear poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having a formula selected from:where a is an integer from 2 to 20 and x is an integer from about 2 to about 50. In some of these embodiments, each of the poly(allyl glycidyl ether succinate) copolymer segments has a degree of polymerization of from about 2 to about 20. In some other embodiments, each of the poly(allylglycidyl ether succinate) copolymer segments has a degree of polymerization of from about 1 to about 10.

[0041] In a sixth aspect, the present invention is directed to a method for making a solvent- free poly(allyl glycidyl ether succinate) resin as described above comprising: preparing a linear poly(allyl glycidyl ether succinate) copolymer having a degree of polymerization of from about 2 to about 20 and a complex viscosity of from about 0.5 Pa.s to about 20.0 Pa.s; adding a photinhibitor to prevent premature crosslinking; adding a multi-functional thiol crosslinker to the mixture to produce a solvent-free poly(allyl glycidyl ether succinate) resin, wherein the molar ratio of allyl groups in said linear poly(allyl glycidyl ether succinate) copolymer to thiol groups in said multi-functional thiol crosslinker is from about 1 : Ito about 20:1; and adding a photoinitiator.

[0042] In one or more embodiments, the method for making a solvent-free poly(allyl glycidyl ether succinate) resins of the present invention include any one or more of the above referenced embodiments of the sixth aspect of the present invention, wherein the linear poly(allyl glycidyl ether succinate) copolymer has the formula:where a is an integer from 2 to 20 and each x is an integer from about 2 to about 50.

[0043] In some embodiments, the method for making a solvent-free poly(allyl glycidyl ether succinate) resins of the present invention include any one or more of the above referenced embodiments of the sixth aspect of the present invention, wherein the linear poly(allyl glycidyl ether succinate) copolymer has a formula selected from:where a is an integer from 2 to 20 and each x is an integer from about 2 to about 50.

[0044] In one or more embodiments, the method for making a solvent-free poly(ally 1 glycidyl ether succinate) resins of the present invention include any one or more of the above referenced embodiments of the sixth aspect of the present invention, wherein the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO). In some embodiments, the method for making a solvent-free poly(allyl glycidyl ether succinate) resins of the present invention include any one or more of the above referenced embodiments of the sixth aspect of the present invention, wherein the step of adding a photoinitiator further comprises adding a light attenuating agent. In some embodiments, the method for making a solvent-free poly(allyl glycidyl ether succinate) resins of the present invention include any one or more of the above referenced embodiments of the sixth aspect of the present invention, wherein the light attenuating agent is oxybenzone. In some embodiments, the method for making a solvent-free poly(allyl glycidyl ether succinate) resins of the present invention include any one or more of the above referenced embodiments of the sixth aspect of the present invention, wherein the light attenuating agent is at least one of 2,2,6, 6-tetramethyl-l-piperidinyloxy (TEMPO) and oxybenzone.

[0045] In a seventh aspect, the present invention is directed to a method for making a low solvent poly(allyl glycidyl ether succinate) resin described above comprising: preparing a linear or star shaped poly(a1 lyl glycidyl ether succinate) copolymer having a degree of polymerization of from about 2 to about 50 and a complex viscosity of from about 20.1 Pa.s to about 0.5 Pa- s; adding an operable amount of a photoinitiator to the linear or star shaped poly(allyl glycidyl ether succinate) polymer; and adding a multi-functional thiol crosslinker to the mixture to produce a solvent-free poly (allyl glycidyl ether succinate) resin; and adding a quantity of a solvent or reactive diluent sufficient to produce a low solvent poly(allyl glycidyl ether succinate) resin having acomplex viscosity of from about 0.5 Pa.s to about 20.0 Pa.s. In one or more of these embodiments, said solvent or reactive diluent comprises less than 20 wt.% of said low solvent poly(allyl glycidyl ether succinate) resin.

[0046] In another aspect, the present invention is directed to a star shaped poly(allyl glycidyl ether succinate) copolymer for use in 3D printing comprising three or more poly(allyl glycidyl ether succinate) copolymer segments each having a degree of polymerization of from about 2 to about 50, wherein said two or more poly(allyl glycidyl ether succinate) copolymer segments are joined to each other through the residue of a multi-functional alcohol initiator.

[0047] In yet another aspect, the present invention is directed to a method for making a linear or star shaped poly(allyl glycidyl ether succinate) copolymer for use in 3D printable resins comprising: dissolving succinic anhydride and allyl glycidyl ether in a suitable solvent under an inert atmosphere; adding a mono, bi- or multi-functional alcohol initiator to the solution; adding a Mg(BHT)2(THF)2 to the solution; heating the mixture to a temperature of from about 60°C to about 120°C for a period of from about 0.5 hours to about 100 hours to produce a linear or star shaped poly(allyl glycidyl ether succinate) copolymer; and collecting and purifying the linear or star shaped poly(allyl glycidyl ether succinate) copolymer.

[0048] In various embodiments, the mono, bi- or multi-functional alcohol initiator is a bi- functional alcohol initiator. In some of these embodiments, the mono, bi- or multi-functional alcohol initiator is a C1-C20 linear diol. In various other embodiments, the mono, bi- or multi- functional alcohol initiator is a multi-functional alcohol initiator has from 3 or 4 reactive hydroxyl groups. In one or more of these embodiments, the multi-functional alcohol initiator is selected from the group consisting of glycerol (propane- 1,2, 3 -triol), meso-erythritol ((2R ,3S)-butane- 1,2,3,4-tetrol), pentaerythritol (2,2-bis(hydroxymethyl)propane-l,3-diol), theitol ((2R,3R)- Butane-1,2,3,4-tetrol), arabitol ((2R ,4R )-pentane-1,2,3,4,5-pentol) xylitol ((2R ,3r,4S)-pentane- 1,2,3,4,5-pentol), adonitol ((2R ,3s,4S)-pentane-1,2,3,4,5-pentol), fucitol ((2R ,3S,4R ,5S)-hexane- 1,2,3,4,5-pentol), sorbitol ((2S,3R,4R,5R)-hexane-1,2,3,4,5,6-hexol), dulcitol ((2R ,3 S,4R ,5S )- hexane-1,2,3,4,5,6-hexol), mannitol (hexane-1,2,3,4,5,6-hexol) Iditol ((2R ,3S,4S,5R )-hexane- 1,2,3,4,5,6-hexol), inositol (1R ,2S,3r,4R ,5S,6s)-cyclohexane-1,2,3,4,5,6-hexol), volemitol ((2R, 3R ,5R ,6R )-heptane-1,2,3,4,5,6,7-heptol), and combinations thereof.BRIEF DESCRIPTION OF THE DRAWINGS

[0049] For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which:

[0050] FIGS. 1 A-B are reaction mechanisms showing: a reaction mechanism for synthesis of PAGES oligomers using ring opening copolymerization of succinic anhydride and allyl glycidyl ether (FIG. 1 A); and PAGES oligomers with DPnof 6, 9 and 16 were 3D printed into tensile bars for mechanical property testing using digital light processing wherein network formation occurred through photochemically activated thiol-ene additions with a trifunctional thiol molecule (FIG 1B).

[0051] FIG. 2 is a graph showing evolution over time of1H-NMR spectra (CDCl3, 20 °C, 600 MHz) during the PAGES polymerization where resonances corresponding to the polymer at δ = 4.3 and δ = 3.6 increase over time while resonances corresponding to the allyl glycidyl ether monomer at δ = 3.7, δ = 3.3, and δ = 3.1 decrease over time. Since allyl glycidyl ether is added in excess, resonances at δ = 3.7, δ = 3.3, and δ = 3.1 will not disappear even when the polymerization has reached completion.

[0052] FIG. 3 is a comparison1H NMR spectra (CDCl3, 20 °C, 600 MHz) of PAGES oligomers with three different degrees of polymerization (DPn): DP6(top), DP9(middle), DP16(bottom). The degree of polymerization can be calculated through relative integration of alkyl (- CH2-) protons in the hexanediol initiator (δ = 1.6 ppm) and methylene (-CH2O(C=O)-) protons in the polymer repeat unit (δ = 4.3 ppm).

[0053] FIG. 4 is an annotated1H NMR spectra (CDCl3, 20 °C, 600 MHz) of a PAGES DP6oligomer according to one or more embodiments of the present invention.

[0054] FIG. 5 is an annotated1H NMR (CDCl3, 20 °C, 600 MHz) of a PAGES DP9oligomer according to one or more embodiments of the present invention.

[0055] FIG. 6 is an annotated1H NMR spectra (CDCl3, 20 °C, 600 MHz) of a PAGES DP16oligomer according to one or more embodiments of the present invention.

[0056] FIG. 7 is a compari son of size exclusion chromatography (SEC) chromatograms (RI detector) of each PAGES polymer (DP6, DP9, DP16) in THF against polystyrene standards (n=1).

[0057] FIGS. 8A-F are graphs characterizing PAGES oligomers showing: Angular frequency sweep rheology of PAGES with DP6(FIG. 8A), DP9(FIG. 8B) and DP16(FIG. 8C) oligomersolutions (wt.%) to determine the solution viscosity at ambient temperature (25°C) wherein the oligomers were diluted with ethyl acetate to achieve the noted concentrations; and the MALDI TOF spectra of PAGES (FIG. 8D), DP6(FIG. 8E), DP9and DP16(FIG. 8F) oligomers used to determine oligomer molecular mass and molar mass distribution.

[0058] FIGS. 9A-F are a series of spectra (FIGS. 9A, C, E) and graphs (FIG. 9B, D, F) of a MALDI-TOF analysis for PAGES oligomers of different DPn(n=1) with the mass of the repeat unit, was determined to be 214 g mol-1from the slope of each linear regression, showing: the raw- spectra of a PAGES DP6. oligomer according to the present invention (FIG. 9 A); a plot of m / z values from MALDI-TOF spectra versus the calculated number of repeat units for a PAGES DP6oligomer according to the present invention wherein the linear regression has an equation y = 214.3x + 139.2 with an R2= 1.000 (FIG. 9B); the raw spectra of a PAGES DP9oligomer according to the present invention (FIG. 9C); a plot of m / z values from MALDI-TOF spectra versus the calculated number of repeat units for a PAGES DP9oligomer according to the present invention wherein the linear regression has an equation y = 214.2x + 157.3 with an R2= 1.000 (FIG. 9D); the raw spectra of a PAGES DP16oligomer according to the present invention (FIG. 9E); and a plot of m / z values from MALDI-TOF spectra versus the calculated number of repeat units for PAGES DP16oligomer according to the present invention where the linear regression has an equation y = 214.6x + 132.5 with an R2= 0.9999 (FIG. 9F).

[0059] FIG. 10 is a 2D1H COSY NMR spectra (CDCl3, 20 °C, 600 MHz) of a PAGES oligomer according to one or more embodiments of the present invention. In the labeled polymer structure, interactions between protons at locations a, b, and c are expected as well as those at locations d, e, and f due to their relative proximity. In the COSY spectra, interactions are confirmed between resonance e with resonances d and f and resonance b with resonances c and a. This confirms that polymer structure is correct.

[0060] FIG. 11 is an annotated 2D1H-13C-Heteronuclear single quantum coherence (HSQC) spectra (CDCl3, 20 °C, 600 MHz) of a PAGES oligomer according to one or more embodiments of the present invention. Using the proton assignments elucidated from COSY NMR spectra, the13C NMR spectra was assigned using the direct coupling between C-H bonds.

[0061] FIG. 12 is a comparison of thermogravimetric analysis (TGA) of each PAGES polymer (DP6, DP9, DP16) used to determine degradation temperature (Td) at 10% mass loss (n=1).

[0062] FIG. 13 is a comparison of differential scanning calorimetry (DSC) thermograms for the second heating cycle of PAGES polymers (DP6, DP9, DP16) used to determine glass transition temperature (Tg) (n=1).

[0063] FIGS. 14A-B are graphs of rheological characterization of neat PAGES polymers. FIG. 14A shows a frequency sweep of each neat PAGES oligomer (DP6, DP9, DP16) at 25 °C (n=1). Neat polymer viscosity values can be used to predict solvent free printability, as previous literature reports that resin viscosity needs to be below 10 Pa.s for DLP printing. With this in mind, the DP6oligomer is expected to print solvent free because the neat polymer is below the viscosity limit, the DP9 oligomer has the possibility to print solvent free because the neat polymer is near the viscosity limit, and the DP16oligomer is not expected the print solvent free because the neat polymer is higher than the viscosity limit. FIG. 14B is a plot showing the relationship between the degree of polymerization and viscosity of the polymer. As can be seen, higher DPnoligomers display higher viscosities.

[0064] FIG. 15 are a schematic diagram and as series of graphs showing the mechanical properties of structures printed with an 80 wt.% polymer resin composition. A) PAGES network formation during 3D printing using digital light processing (DLP) through thiol-ene addition crosslinking. Crosslinked networks include small amounts of defects such as loops and dangling ends.

[0065] FIG. 16 is a schematic diagram showing formation of a crosslinked network of PAGES polymer using trimethylolpropane tris(3 -mercaptopropionate) crosslinker via thiol-ene addition during the DLP 3D printing process.

[0066] FIG. 17 is a comparison of frequency sweeps of neat PAGES DP6oligomer before and after 15 mins in a UV oven (n=1). The curves are the same, indicating that no crosslinking occurs without the multifunctional thiol molecule.

[0067] FIGS. 18A-B is a comparison of Fourier-Transform Infrared Spectroscopy (FT-IR) spectra of the multifunctional thiol crosslinker, neat polymer, and each solid 3D printed polymer printed at a 5: 1 crosslink ratio after printing and curing (n=1) and showing: full spectra for the thiol crosslinker, neat PAGES oligomer, DP6oligomer printed at a 5:1 crosslink ratio, DP6oligomer printed at a 5:1 crosslink ratio, and DP6oligomer printed at a 5: 1 crosslink ratio with the S-H stretching region is highlighted in gray (S-II stretch appears for the thiol crosslinker but not in any printed parts which confirms that all thiols reacted in the thiol-ene addition reaction thatoccurs during crosslinking) (FIG. 18A); zoomed spectra for the thiol crosslinker, neat PAGES oligomer, DP6oligomer printed at a 5:1 crosslink ratio, DP6oligomer printed at a 5: 1 crosslink ratio, and DP6oligomer printed at a 5:1 crosslink ratio with the C=C bending region is highlighted in gray (FIG. 18B). The C=C bending is expected to be visible in printed parts due to sub- stoichiometric crosslinking.

[0068] FIGS. 19A-C are images of 3D printed samples showing: DP165: 1 prints on the build tray immediately after printing (FIG. 19 A); the build tray layout used for each print (FIG. 19B); and an example tensile bar from each print after being cleaned and cured (FIG. 19C).

[0069] FIG. 20 is a graph showing the critical gel point to prints of DP65:1, DP95:1, DP165:1, DP1610:1, DP1620:1, and DP9 10:1, as calculated using Equation 1. The line representing the critical gel point equal to one is a threshold for print quality.

[0070] FIG. 21 is a graph showing crosslinkers per chain for DP65:1, DP95:1, DP165: 1, DP1610:1, DP1620:1, and DP9 10:1, as calculated by the ratio of DPnto crosslink ratio. The line representing the number of crosslinks per chain equal to one is a threshold for print quality.

[0071] FIG. 22 is a graph showing the number of crosslinks per chain versus crosslink density (q) for DP65:1, DP9 5:1, DP165:1, DP1610:1, DP1620: 1, and DP9 10:1 polymer resins where the linear regression has an equation y = 0.56x + 1 .23 with an R2= 0.9370. The positive slope indicates a positive correlation between crosslink density and number of crosslinks per chain, as expected since both measure the amount of crosslinking in a network.

[0072] FIG. 23 in an image of ASTM D638 Type V 3D printed tensile bars of the DP165: 1, polymer resin with sand paper attached on the edge tabs to decrease the likeliness of sample slippage during tensile testing.

[0073] FIGS. 24A-C are a comparison of representative stress-strain curves for prints of DP65:1, DP95:1, and DP165:1 (FIG. 24A), a comparison of representative stress-strain curves for prints of DP165:1, DP1610:1, and DP1620: 1 (FIG. 24B), and a comparison of representative stress- strain curves for prints of DP1620:1 and DP9 10:1 (FIG. 24C).

[0074] FIG. 25 is a graph showing stress strain curves produced from uniaxial tensile testing of five 3D printed DP65:1 samples printed with an 80% polymer resin composition.

[0075] FIG. 26 is a graph showing stress strain curves produced from uniaxial tensile testing of five 3D printed DP9 5:1 samples printed with an 80% polymer resin composition (n=5).

[0076] FIG. 27 is a graph showing stress strain curves produced from uniaxial tensile testing of five 3D printed DP165: 1 samples printed with an 80% polymer resin composition (n=5).

[0077] FIG. 28 is a graph showing stress strain curves produced from uniaxial tensile testing of five 3D printed DP1610: 1 samples printed with an 80% polymer resin composition (n=5).

[0078] FIG. 29 is a graph showing stress strain curves produced from uniaxial tensile testing of five 3D printed DP1620: 1 samples printed with an 80% polymer resin composition (n=5).

[0079] FIG. 30 is a graph showing stress strain curves produced from uniaxial tensile testing of five 3D printed DP910: 1 samples printed with an 80% polymer resin composition (n=5).

[0080] FIG. 31 is a graph showing strain at break during uniaxial tensile testing for prints of DP65:1, DP95:1, DP165: 1, DP1610:1, DP1620:1, and DP910:1 with an 80% polymer resin composition (n = 5). Box plots show median, first quartile, third quartile, maximum, and minimum. All groups show insignificant difference unless otherwise indicated. Degree of statistical significance determined using Tukey’s multiple comparisons test with *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

[0081] FIG. 32 is a graph showing ultimate tensile strength measurements for prints of DP65: 1, DP95:1, DP165: 1, DP1610:1, DP1620:1, and DP910: 1 with an 80% polymer resin composition (n = 5). Box plots show median, first quartile, third quartile, maximum, and minimum. All groups show significant difference unless otherwise indicated. Statistical significance determined using Tukey’s multiple comparisons test with significance indicated by p < 0.05.

[0082] FIGS. 33 A-B are a schematic diagram and as series of graphs showing the mechanical properties of structures printed with an 80 wt.% polymer resin composition showing the tensile modulus (FIG. 33A) of each formulation (n=5) exhibited statistically significant differences (Tukey’s multiple comparisons test with p < 0.05) among prints with different DPnand crosslink ratio except as noted and the ensile modulus of each formulation plotted against the normalized value of crosslinks per chain (n=5) (FIG. 33B).

[0083] FIG. 34 is a graph showing representative elongational storage modulus values for prints of DP65:1, DP95:1, DP165:1, DP1610:1, DP1620: 1, and DP910:1 determined using the DMA frequency sweeps of bars from each print with an 80% polymer resin composition.

[0084] FIG. 35 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of three bars printed from DP65:1 with an 80% polymer resin composition.

[0085] FIG. 36 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of three bars from prints of DP9 5:1 with an 80% polymer resin composition.

[0086] FIG. 37 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of three bars of from DP165: 1 prints with an 80% polymer resin composition.

[0087] FIG. 38 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of three bars of DP1610:1 prints with an 80% polymer resin composition.

[0088] FIG. 39 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of three bars of DP1620:1 prints with an 80% polymer resin composition.

[0089] FIG. 40 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of three bars of DP910:1 prints with an 80% polymer resin composition.

[0090] FIG. 41 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of bars for prints of DP65:1, DP95:1, DP165:1, DP1610:1, DP1620:1, and DP910:1 with an 80% polymer resin composition (n = 3). Error bars represent standard deviation. All groups show significant differences unless otherwise indicated. Statistical significance determined using Tukey’s multiple comparisons test with significance indicated by p < 0.05.

[0091] FIG. 42 is a graph showing the number of crosslinks per chain versus elongational storage modulus determined using DMA frequency sweeps for DP65:1, DP95:1, DP165:1, DP1610:1, DP1620:1, and DP910:1 polymer resins where the linear regression has an equation y = 0.8975x - 0.3197 with an R2= 0.9561. The regression displays an x-intercept of 0.36, which indicates that this system requires a minimum of 0.36 crosslinks per chain to form a sample- spanning network. This indicates that the network requires at approximately one crosslink for every three polymer chains, which confirms the network structure formed using the trifunctional crosslinker.

[0092] FIGS. 43A-D are a series of graphs of the mechanical properties of structures printed with an 80 wt.% polymer resin composition showing the elongational storage modulus and tan(5) curves obtained from DMA of each formulation with a 5: 1 crosslink ratio shift proportionally with chain length (FIGS. 43 A-B) and the elongational storage modulus and tan(δ) curves obtained from DMA of each formulation with DP16polymer shift proportionally with crosslink ratio (FIGS. 43C- D).

[0093] FIGS. 44A-C are a seri es of graphs of the degradation and swelling of DMA. bars (18 x 3.6 x 2.4 mm) printed (80 wt.% polymer) at each of the respective formulations showing:accelerated degradation (I N NaOH) of each formulation with agitation at 37 °C (n=5) (FIG. 44A); swelling of each formulation after 48 hours in ethyl acetate (n=3) with all groups having statistically signifi cant differences (FIG. 44B); and sol fraction of each formulation after 48 hours in ethyl acetate (n=3) (FIG. 44C) with all of the groups having statistically significant differences except DP65:1 versus DP1620:1 and DP95:1 versus DP1610:1. Error bars represent standard deviation and the statistical significance determined using Tukey’s multiple comparisons test with significance indicated by p < 0.05.

[0094] FIG. 45 is a graph showing the number of crosslinks per chain versus swelling percentage in ethyl acetate after 48 hours for DP65:1, DP95: 1, DP165:1, DP1610: 1, DP1620:1, and DP910:1 polymer resin where the linear regression has an equation y = -10.60x + 83.23 with an R2= 0.8875. The negative slope indicates that increased crosslinking results in less swelling.

[0095] FIG. 46 is a graph showing the crosslink density (q) versus swelling percentage in ethyl acetate after 48 hours for DP65:1, DP95:1, DP165:1, DP1610:1, DP1620:1, and DP910:1 polymer resin where the linear regression has an equation y = -6.26x + 74.67 with an R2 :::0.7620. The negative slope indicates that increased crosslink density results in less swelling.

[0096] FIG. 47 is a graph showing the number of crosslinks per chain versus sol fraction in ethyl acetate after 48 hours for DP65: 1, DP95:1, DP165: 1, DP1610:1, DP1620:1, and DP910:1 polymer resin where the linear regression has an equation y = -11 ,04x + 40.35 with an R2= 0.7111. The negative slope indicates that increased crosslinking results in a lower sol fraction.

[0097] FIG. 48 is a graph showing the crosslink density (q) versus sol fraction in ethyl acetate after 48 hours for DP65:1, DP95:1, DP165:1, DP1610: 1, DP1620:1, and DP910:1 polymer resin where the linear regression has an equation y = -7.00x + 32.06 with an R2= 0.7036. The negative slope indicates that increased crosslink density results in a lower sol fraction.

[0098] FIGS. 49A-G are graphs of the results of a physical and mechanical analysis of low solvent and solvent free networks according to the present invention showing: part thickness shrinkage showing how much printed parts diverge from their intended dimensions as specified by the . stl file input into the printer (n=5) wherein a statistically significant difference was found between all groups within each DPn(FIG. 49 A); an elongational storage modulus obtained from DMA frequency sweeps of each formulation (n=3) demonstrating a statistically significant difference between DP680% and 99+% groups as well as between DP980% and 99+% groups (FIG. 49B); representative stress-strain curves from the DP6 formation (FIG. 49C) and DP9formulation (FIG. 49D); the tensile modulus of the DP6 and DP9 formulations (n=5) showing a statistically significant difference between DP9 groups (FIG. 49E); swelling of the DP6 and DP9 formulations after 48 hours in ethyl acetate (n=3) demonstrating a statistical significance between each DP6solvent-containing group and the DP6solvent free group as well as between DP9 80% and 99+% groups (FIG. 49F); and the sol fraction of DP6 and DP9 formulations after 48 hours in ethyl acetate (n=3) (FIG. 49G). The error bars represent standard deviation and the degree of statistical significance determined using Tukey’s multiple comparisons test with *p < 0.05, **p <0.01, ***p < 0.001, ****p < 0.0001.

[0099] FIG. 50 is a graph of the elongational storage modulus determined using DMA frequency sweeps of bars from DP65:1 prints with 90% polymer resin composition.

[0100] FIG. 51 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of three bars from DP65:1 prints with 95% polymer resin composition.

[0101] FIG. 52 is a graph showing the elongational storage modulus determined using DMA frequency sweeps of from DP65:1 prints with 99+% polymer resin composition.

[0102] FIG. 53 are stress strain curves produced from uniaxial tensile testing from 5 3D printed DP65:1 samples printed with 90% polymer resin composition (n::::5).

[0103] FIG. 54 are stress strain curves produced from uniaxial tensile testing from 5 3D printed DP65:1 samples printed with 95% polymer resin composition (n=5).

[0104] FIG. 55 are stress strain curves produced from uniaxial tensile testing from 5 3D printed DP65:1 samples printed with 99+% polymer resin composition (n=5).

[0105] FIG. 56 is a graph showing strain at break for each DP65:1 print with 80%, 90%, 95%, and 99%+ polymer resin composition (n = 5). Error bars represent standard deviation. No statistically significant differences between groups were observed. Statistical significance determined using Tukey’s multiple comparisons test with significance indicated by p < 0.05.

[0106] FIG. 57 is a graph showing the ultimate tensile strength for each DP65: 1 print with polymer resin compositions of 80%, 90%, 95%, and 99%+ (n = 5). Error bars represent standard deviation. A statistically significant difference was only found for 90% vs 95% samples and 90% vs 99+% samples. Degree of statistical significance determined using Tukey’s multiple comparisons test with *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

[0107] FIGS. 58A-B is a graph showing the elongational storage modulus (FIG. 58A) and tan(5) (FIG. 58B) curves obtained from DMA temperature sweeps of each DP65:1 print made with polymer resin composition of 80%, 90%, 95%, and 99%+ (n = 1).

[0108] FIG. 59 is a graph showing stress strain curves produced from uniaxial tensile testing 3D printed DP95:1 samples printed with 99+% polymer resin composition (n=5).

[0109] FIG. 60 is a graph showing strain at break for each DP95: 1 print with polymer resin compositions of 80% and 99%+ (n = 5). Error bars represent standard deviation. A statistically significant difference between groups was observed. Degree of statistical significance determined using Tukey’s multiple comparisons test with *p < 0.05, **p <0.01, ***p< 0.001, ****p < 0.0001.

[0110] FIG. 61 is a graph showing ultimate tensile strength for each DP95:1 print with varying polymer resin compositions of 80% and 99%+ (n = 5). Error bars represent standard deviation. A statistically significant difference between groups was observed. Degree of statistical significance determined using Tukey’s multiple comparisons test with *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

[0111] FIG. 62 is a graph showing the elongational storage modulus determined through DMA frequency sweeps of three bars from DP95:1 prints with 99+% polymer resin composition.

[0112] FIGS. 63A-B are graphs showing the elongational storage modulus (FIG. 63A) and tan(5) (FIG. 63B) curves obtained from DMA temperature sweeps of each DP95: 1 print made with polymer resin composition of 80% and 99%+ (n = 1).

[0113] FIGS. 64A-E are images of hhigh resolution solvent free 3D printing of a resin formulation according to the present invention including the PAGES DP6polymer, 0.5 wt.% BAPO, 0.01 wt.% TEMPO, 0.04 wt.% Sudan I, and thiol crosslinker PAGES DP6, formed at a 5:1 crosslink ratio, and showing: a solvent free 3D Benchy (FIG. 64A) (scale bar represents 10 mm); a side perspective view micro-computed tomography (pCT) image of solvent free 3D Benchy (FIG. 65B) (scale bar represents 10 mm); C) a top view pCT image of solvent free 3D Benchy (FIG. 65C) (scale bar represents 10 mm); a side view pCT image of solvent free gyroid structure (FIG. 64D) (scale bar represents 3 mm); and a top view pCT image of solvent free gyroid structure (scale bar represents 3 mm) (FIG. 64E).

[0114] FIG. 65 is a sscanning electron microscopy (SEM) image of one pore within the gyroid structure of FIGS. 64D-E (scale bar represents 500 μm) showing 100 μm thick print layers withinthe pore. It is believed that the grid pattern visible on the top surface of the gyroid is caused by the pixels of the light engine in the 3D printer.

[0115] FIGS. 66 are images of solvent free high resolution samples showing: a front view / of solvent free 3D Benchy (FIG. 66A); a top view of solvent free 3D Benchy (FIG. 66B); a side view of solvent free gyroid structure (FIG. 66C); and a top view of a solvent free gyroid structure (FIG. 66D). All scale bars represent 10 mm.

[0116] FIG. 67 is a1H-NMR of purified MIS-I-140 in CDCh.

[0117] FIG. 68 is a13C-NMR of purified MIS-I-140 in CDCl3.

[0118] FIG. 69 is a1H-1H-COSY NMR of purified MIS-I-140 in CDCl3.

[0119] FIG. 70 is a graph of normalized RI SEC curves of each batch of PAGES polymer inTHF

[0120] FIG. 71 is a frequency sweep of MIS-I-140 dissolved with various weight percentages of ethyl acetate. The percentage displayed corresponds to the weight percent of PAGES polymer; the remaining percentage is the weight percent of ethyl acetate.

[0121] FIG. 72 is a MALDI-TOF curve of MIS-I-140.

[0122] FIG. 73 is a MALDI-TOF curve of MIS-I-166.

[0123] FIG. 74 is a DSC curve of MIS-I-140 showing the Tgoccurring at the midpoint of the transition in the second heating cycle.

[0124] FIG. 75 is a graph of TGA curves of PAGES samples.

[0125] FIG. 76 is a frequency sweep of pure PAGES samples with no solvent.

[0126] FIG. 77 is a FTIR curve of MIS-I-140.

[0127] FIG. 78 is a graph showing stress strain curves generated during uniaxial tensile testing at room temperature of MIS-I-166 at a 5: 1 crosslink ratio.

[0128] FIGS. 79A-C are graphs showing the results of a part shrinkage study of all cured samples printed with an 80% polymer resin composition showing: (i) length shrinkage (FIG. 79A), width shrinkage (FIG. 79B) and thickness shrinkage (FIG. 79C); (ii) how much printed parts diverge from their intended dimensions as specified by the .stl file input into the printer. Box plots show median, first quartile, third quartile, maximum, and minimum. All groups show significant difference unless otherwise indicated. All measurements were completed on tensile bar specimens (n=5) and statistical significance determined using Tukey’s multiple comparisons test withsignificance indicated by p < 0.05. The term “ nnss” in the graphs means “not significant” as determined using one-way ANOVA tests and Tukey’s multiple comparisons tests.

[0129] FIGS. 80A-C are a series of graphs reflecting the results of a part shrinkage study and showing the thickness shrinkage (FIG. 80A), width shrinkage (FIG. 80B), and length shrinkage (FIG. 80C) of all samples pri nted at DP65:1 using polymer resin compositions of 80%, 90%, 95%, and 99%+, and also showing how much printed parts diverge from their intended dimensions as specified by the . stl file input into the printer. All measurements were completed on tensile bar specimens (n = 5). Error bars represent standard deviation. Statistical significance determined using Tukey’s multiple comparisons test with significance indicated by p < 0.05.

[0130] FIGS. 81 are a series of graphs reflecting the results of a part shrinkage study of all samples printed at DP95: 1 with polymer resin composition of 80% and 99%+ showing length shrinkage (FIG. 81 A) width shrinkage (FIG. 81B) thickness shrinkage (FIG. 81C), as well as how much the printed parts diverge from their intended dimensions as specified by the .stl file input into the printer. All measurements were completed on tensile bar specimens (n = 5). Error bars represent standard deviation. A statistically significant difference between all groups was observed. Degree of statistical significance determined using Tukey’s multiple comparisons test with *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

[0131] The following is a detailed description of the disclosure provided to aid those skilled in the art in practicing the present disclosure. Those of ordinary skill in the art may make modifications and variations in the embodiments described herein without departing from the spirit or scope of the present disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description of the disclosure herein is for describing particular embodiments only and is not intended to be limiting of the disclosure.

[0132] In various embodiments, the present invention provides a solvent free 3D printable resin comprising poly(allyl glycidyl ether succinate) (“PAGES”) copolymer, and a multi- functional thiol crosslinker, as set forth above. In one or more of these embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) copolymer will be formed by ring opening copolymerization of allyl glycidyl ether and succinic anhydride, initiated by a mono-, bi-, or multi-functionalinitiating alcohol and using a 2,6-di-tert-butyl-4-methylphenoxide (Mg(BHT)2(THF)2) catalyst. Advantageously, it has been reported that these resins have a complex viscosity that is suitable for 3D printing (from about 0.5 Pa.s to about 20.0 Pa.s) at room temperature without the need for a solvent or other diluent.

[0133] The architecture of the PAGES copolymers of the present invention was inspired by a comb polymer architecture with side chains that do not entangle, contributing to lower viscosity under ambient conditions. Stochiometric control over PAGES polymerization allows for targeted degree of polymerization (DPn) and viscosity values while also enabling large-scale synthesis approaching Kg scale, even in an academic laboratory. As set forth above, these PAGES copolymers exhibits a direct correlation between oligomer molecular mass and degree of crosslinking with mechanical properties and degradation profile, which allows for prospective design of materials.

[0134] When used in combination with degradable thiol crosslinkers, these PAGES copolymers have been found in vari ous embodiments to afford a solvent free DLP 3D printi ng system. That is, in one or more embodiments, these PAGES copolymers can be 3D printed using vat photopolymerization techniques like digital light processing (DLP) without the need to incorporate a solvent or reactive diluent into the resin. Advantageously, it has been found that these resins have a complex viscosity that is suitable 3D printing (from about 0.5 Pa.s to about 20 Pa.s) without the need for a solvent or other diluent. Moreover, because they have no solvent, these resins avoid the problems with shrinkage and the attendant increase in stress to the printed polymer structure that ordinarily happens when the residual solvent is removed. Varying resin formulations of PAGES polymer are shown to decrease part shrinkage from 14% to 0.3%. 3D printed parts fabricated from PAGES possess tensile modulus values between 0.43 and 6.18 MPa and degradation profiles are shown to vary between 12 and 40 days under accelerated conditions based on polymer degree of polymerization and crosslink ratio.

[0135] As set forth above, these resins may also include an operable amount of at least one suitable photoinitiator, such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) and a light attenuating agent or photoinhibitor, such as oxybenzone or TEMPO. As would be understood by those of skill in the art, an “operable amount” refers to an amount of a material greater than or equal to the minimum amount of a material needed to provide a desired function. One of ordinaryskill would be able to arrive at an operable amount of photoinitiator or photoinhibitor without undue experimentation.

[0136] The following terms may have meanings ascribed to them below7, unless specified otherwise. As used herein, the terms "comprising," "to comprise" and the like do not exclude the presence of further elements or steps in addition to those listed in a claim . Similarly, the terms “a,” “an” or “the” before an element or feature does not exclude the presence of a plurality of these elements or features, unless the context clearly di ctates otherwise

[0137] Unless specifically stated or obvious from context, as used herein, the term "about" is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. "About" can be understood as within 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein in the specification and the claim can be modified by the term "about."

[0138] It should be also understood that the ranges provided herein are a shorthand for all of the values within the range and, further, that the individual range values presented herein can be combined to form additional non-disclosed ranges. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group con si sting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50.

[0139] The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0140] As used herein, the term “3D printable,” as applied to a polymer or copolymer, refers to a polymer or copolymer that can be used alone or with other ingredients to form a resin capable of be printed into a 3-dimensional (3D) structure using conventional additive manufacturing (3D printing) technologies. As follows, when applied to a resin composition, the term “3D printable” refers to composition containing a polymer or copolymer, alone or with other ingredients, that can be loaded into a conventional additive manufacturing (3D printing) device and printed to form a 3D structure.

[0141] As used herein, the term “photocrosslinkable” as applied to a polymer, copolymer, or resin, refers to the presence of functional groups that will crosslink with functional groups of thesame polymer or another polymer or copolymer by application of photons (e.g., UV light) alone or in the presence of a photoinitiator. Similarly, the terms “photopolymerizable” and “3D photopolymerizable” as applied herein to a polymer, copolymer, or resin, refers to the ability of a. polymer, copolymer, or resin to polymerize or crosslink by application of photons (e.g., UV light) alone or in the presence of a photoinitiator.

[0142] The term “photoinitiator" is used herein to refer to a substance that undergoes a reaction to form radicals while being irradiated with light and can subsequently transfer formed radicals to another molecule for use in consecutive reactions. The terms “photoinhibitor and “light attenuating agent” are used herein interchangeably to refer to a substance that absorbs light to prevent excess radical formation, thus helping to suppress unintended reactions.

[0143] Further, as used herein, the terms “solvent free” or “solvent-free” as applied to a 3D printable resin refers to a resin capable of being 3D printed that contains 1.5 wt.% or less, preferably 1 wt.% or less, and more preferably 0.1 wt.% or less, solvent or diluent. That is, no solvent or diluent is added to form a 3D photopolymerizable resin having a complex viscosity suitable for use with conventional light-based 3D printers. Similarly, the terms “low solvent,” “low-solvent,” “reduced solvent,” and “reduced-solvent” are used interchangeably to refer to a 3D printable resin refers to a resin capable of being 3D printed that contains 20 wt.% or less, preferably 10 wt.% or less, and more preferably 5 wt.% or less, solvent or diluent. In these embodiments, diluent or solvent must be added to form a photopolymerizable resin with a complex viscosity that is suitable for use with conventional light-based 3D printers, but the amount of diluent or solvent required is less than what must be added to form conventional 3D printable resins made with other resorbable polymers like polypropylene fumarate) (PPF), poly(lactic acid), poly(lactide-co- glycolide), polycarbonate, polyurethanes, etc.

[0144] As used herein, a “biocompatible” material is one which stimulates only a mild, often transient, implantation response, as opposed to a severe or escalating response. As used herein, a “biodegradable” material is one which decomposes under normal in vivo physiological conditions into components which can be metabolized or excreted. And as used herein, a “resorbable” or “bioresorbable” material is one that breaks down over a. finite period of time due to the chemical / biological action of the body.[00.145] As used herein to refer to a molecule or functional group, the term “linear” refers to a molecule or functional group that does not possess branching units; similarly, a molecule orfunctional group may be referred to herein as “substantially linear” where the mole fraction of branching units does not exceed 2 % of the molecule or functional group. In the context of a polymer or copolymer, the terms “star polymer,” “star-shaped," and “multi-arm” are used herein interchangeably to refer to a polymer or copolymer having 3 or more arms extending outward from a central core structure. As used herein, the term “arm” refers to a substantially linear polymer or copolymer chain that is bonded at one end to a central core structure and extends outward therefrom.

[0146] The terms “functionalized initiating alcohol” and “functional initiating alcohol” are is used herein interchangeably to refer to an alcohol molecule capable of initiating ring opening copolymerization of a succinic anhydride monomer and an allyl glycidyl ether monomer, in the presence of Mg(BHT)2(THF)2 catalyst. A functionalized initiating alcohol having a single hydroxyl group capable of initiating ring opening copolymerization of a succinic anhydride monomer and an allyl glycidyl ether monomer, in the presence of Mg(BHT)2(THF)2 catalyst will be referred to herein interchangeably as a “mono-functional initiating alcohol,” “mono functional initiating alcohol,” “mono-functionalized initiating alcohol initiating alcohol” or “mono functionalized initiating alcohol initiating alcohol.” As follows, he terms “residue of the mono- functionalized initiating alcohol” or “mono-functionalized initiating alcohol residue” and the like, refer to the parts of the mono-functionalized initiating alcohol that remain bound at the end of the PAGES copolymer chain after it initiates polymerization.

[0147] Similarly, the terms “bifunctional alcohol initiator” “bifunctionalized alcohol initiator,” “bi -functional alcohol initiator,” and “bi-functionalized alcohol initiator” are used interchangeably herein to refer to a functionalized initiating alcohol having two active hydroxyl groups, each capable of initiating ring opening copolymerization of a succinic anhydride monomer and an allyl glycidyl ether monomer, in the presence of Mg(BHT)2(THF)2 catalyst. As follows, the terms “residue of the bi-functionalized initiating alcohol” or “bi-functionalized initiating alcohol residue” and the like, refer to the parts of the mono-functionalized initiating alcohol that remain bound at the end of the PAGES copolymer chain after it initiates polymerization.

[0148] Similarly, the terms “multifunctional alcohol initiator,” “multi-functional alcohol initiator," “multifunctionalized alcohol initiator,” “multi-functionalized alcohol initiator” are used interchangeably to refer to a functional initiating alcohol having three or more active hydroxyl groups, each capable of initiating ring opening copolymerization of a succinic anhydride monomerand an allyl glycidyl ether monomer, in the presence of Mg(BHT)2(THF)2 catalyst. As follows, the terms “residue of the multi -functionalized initiating alcohol” or “bi-functionalizedized initiating alcohol residue” and the like, refer to the parts of the mono-functionalized initiating alcohol that remain bound at the end of the PAGES copolymer chain after it initiates polymerization.

[0149] Generally, a “ring opening polymerization” reaction is defined as a reaction in which two or more cyclic monomers repeatedly react with a terminal reactive center, thus opening their rings during the successive polymerization. Similarly, the term “ring opening copolymerization” is used to refer to a ring opening polymerization having two or more different cyclic monomers.

[0150] As used herein, the “degree of polymerization” (DP) generally refers to the number of monomer repeat units present in a given polymer chain. As applied to polymer or copolymer having two or more arms extending from a central core, such as a star polymer, the DP will be the number of monomer repeat unit in each arm extending from a central core.

[0151] As used herein, the term “crosslinker” refers to a molecule that is capable of reacting with two or more polymer chains in order to link them together.

[0152] As used herein to apply to a polymer, copolymer or resin, the term “neat” is used herein to refer to a polymer without solvent or diluent.

[0153] As used herein, the term “polymer resin composition” is used herein to refer to the portion of the reduced solvent or, preferably, solvent free 3D printable resin comprising the PAGES copolymers and diluent (if any), exclusive of the multifunctional thiol crosslinkers and other components. In various embodiments, the PAGES copolymers will comprise from about 64 wt.% to more than 99 wt.% of the polymer resin composi tion. As follows, the term 80% polym er resin composition refers to a polymer resin composition having 80% PAGES copolymer and 20% diluent, the term 85% polymer resin composition refers to a polymer resin composition having 85% PAGES copolymer and 15% diluent, the term 80% polymer resin composition refers to a polymer resin composition having 90% PAGES copolymer and 10% diluent, the term 95% polymer resin composition refers to a polymer resin composition having 95% PAGES copolymer and 5% diluent, the term 99+% polymer resin composition refers to a polymer resin composition having 99% or more PAGES copolymer and less than 1% diluent, by weight.

[0154] As used herein, the terms “sol fraction” and “sol-fraction” are used interchangeably to refer to the proportion of a printed part that is made up of unlinked polymer chains that do not contribute to the elastic properties of the solid.

[0155] Ail publications, patent applications, patents, and other references mentioned herein are expressly incorporated by reference in their entirety, which means that they should be read and considered by the reader as part of this text. That the document, reference, patent application, or patent cited in this text is not repeated in this text is merely for reasons of conciseness. In the case of conflict, the present disclosure, including definitions, will control. All technical and scientific terms used herein have the same meaning, unless otherwise indicated.

[0156] Further, any compositions or methods provided herein can be combined with one or more of any of the other compositions and methods provided herein. The fact that given features, elements or components are cited in different dependent claims does not exclude that at least some of these features, elements, or components maybe used in combination together.

[0157] In a first aspect, the present invention is directed to a linear or star-shaped poly(allyl glycidyl ether succinate) (“PAGES”) copolymer for use in reduced solvent and / or solvent-free resin for 3D printing, as described below. In various embodiments, the present invention is directed to a solvent free 3D printable resin comprising a linear or star-shaped poly(allyl glycidyl ether succinate) (“PAGES”) copolymer and a multi-functional thiol crosslinker. Surprisingly, it has been that these resins have a complex viscosity (q) that is suitable 3D printing (from about 0.5 Pa.s to about 20 Pa.s) without the need for a solvent or other diluent.

[0158] In one or more embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) copolymer will be a linear or star copolymer formed by ring opening copolymerization of allyl glycidyl ether and succinic anhydride, initiated by a mono-, bi-, or multi-functional initiating alcohol and using Mg(BHT)2(THF)2 catalyst. In various embodiment, the linear’ or star PAGES copolymer will have a degree of polymerization from about 2 to about 50. In some embodiments, the linear or star PAGES copolymer will have a degree of polymerization from about 2 to about 40, in other embodiments, from about 5 to about 30, in other embodiments, from about 2 to about 20, in other embodiments, from about 2 to about 10, in other embodiments, from about 10 to about 50, in other embodiments, from about 20 to about 50, in other embodiments, from about 30 to about 50, and in other embodiments, from about 10 to about 20. In some other embodiments, the linear or star PAGES copolymer will have a degree of polymerization from about 15 to about 25. In some of these embodiments, the linear or star PAGES copolymer used to form the solvent free resin of the present invention will have a degree of polymerization (DP) of 20. Here, as well aselsewhere in the specification and claims, individual range values can be combined to form additional non-disclosed ranges

[0159] In one or more embodiment, the poly(allyl glycidyl ether succinate) (“PAGES”) copolymer will have a formula selected from:a is an integer from 2 through 20, and x is an integer from about 2 to about 50.

[0160] In some embodiments, a will be an integer from 2 to 18, in other embodiments, from about 2 to about 16, in other embodiments, from about 2 to about 14, in other embodiments, from about 2 to about 12, in other embodiments, from about 2 to about 10, in other embodiments, from about 2 to about 8, in other embodiments, from about 2 to about 6, in other embodiments, from about 4 to about 20, in other embodiments, from about 6 to about 20, in other embodiments, from about 8 to about 20, in other embodiments, from about 10 to about 20, in other embodiments, from about 12 to about 20 and in other embodiments, from about 14 to about 20. In some of these embodiments, a is 6. In some embodiments, x is an integer from about 2 to about 40, in other embodiments, from about 2 to about 30, in other embodiments, from about 2 to about 20, in other embodiments, from about 2 to about 10, in other embodiments, from about 10 to about 50, in other embodiments, from about 20 to about 50, in other embodiments, from about 30 to about 50, and in other embodiments, from about 40 to about 50. In some other embodiments, from about 15 to about 25. In some of these embodiments, x is 20. Here, as well as elsewhere in the specification and claims, individual range values can be combined to form additional non-disclosed ranges.

[0161] In various embodiments, the linear or star-shaped 3D printable PAGES copolymers used for the solvent free resins of the present invention are formed by ring opening copolymerization of allyl glycidyl ether and succinic anhydride, initiated by a mono-, bi-, or multi -functional initiating alcohol and using a Mg(BHT)2(THF)2 catalyst, as set forth above and described in more detail below. As will be apparent, the central core structure of these linear or star-shaped PAGES copolymers will comprise the residue of the mono, bi-, or multi-functional alcohol used to as the initiator and the number of arms on these polymers is likewise controlled by the number of alcohol (i.e. hydroxyl) functional groups present on the multi-functional alcohol initiator. As used herein, the term “residue(s)” is used to refer generally to the portion of a monomer or other chemical unit that has been incorporated into a polymer or other large molecule. The PAGES copolymers of the present invention may, therefore, be linear or star shaped, depending upon they type of initiating alcohol used to form the polymer. In either case, the residue of the initiating alcohol used to form the copolymer will form the core structure from which the PAGES copolymer chains will extend.

[0162] In embodiments where the PAGES copolymers are to have a generally linear structure, a mono-functional or bi-functional alcohol initiator will be used. In embodiments where a mono- functional alcohol initiator is used to initiate the ring opening copolymerization reaction and the resulting polymers will have a single PAGES chain emanating outward from the residue of the initiating alcohol, which will be located on one end of the polymer chain. Suitable mono-functional alcohol initiators are not particularly limited and may include, without limitation, propargyl alcohol, benzyl alcohol, allyl alcohol, 4-dibenzyocyclooctynol, 4-hydroxybutan-2-one, 3- hydroxypropan-2-one, 5-hydroxypentan-2-one, 6-hydroxyhexan-2-one, 7-hydroxyheptan-2-one, 8-hydroxyoctan-2-one, 5-norbomen-2-ol, a-bromoisobtyryl 4-methanol benzylmethanoate or a combination thereof. In some embodiments, the mono-functional alcohol initiator is propargyl alcohol.

[0163] In one or more embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) polymer will be a linear copolymer having the formula:where R is a residue of a mono-functional initiating alcohol and x is an integer from 2 to 50. In various embodiments, x may be as set forth above.

[0164] In one or more embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) polymer will be a linear copolymer having the formula:where x is an integer from 2 to 50. In various embodiments, x may be as set forth above.

[0165] In some other embodiments, a bifunctional alcohol initiator is used to initiate the ring opening copolymerization reaction and the resulting polymers having two PAGES chains (arms) emanating outward from a core structure. These copolymers will have a generally linear configuration, the present invention is directed to a linear poly(allyl glycidyl ether succinate) copolymer for use in 3D printing comprising two poly(allyl glycidyl ether succinate) copolymer segments each having a degree of polymerization of from about 2 to about 100 wherein said two poly(allyl glycidyl ether succinate) copolymer segments are joined to each other through the residue of a bi- functional alcohol initiator. In some of these embodiments, the linear poly(allyl glycidyl ether succinate) copolymer comprises the ring opening copolymerization reaction product of succinic anhydride and allyl glycidyl ether using a bi-functional alcohol initiator and Mg(BHT)2(THF)2 catalyst, as described below.

[0166] In one or more embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) polymer will be a linear copolymer having the formula:where a is an integer from 2-20 and x is an integer from about 1 to about 50. In various embodiments, a and x may be as set forth above.

[0167] In some of these embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) copolymer will be a linear copolymer having the formula selected from:where a is an integer from 2-20 and each x is an integer from about 2 to about 50. In various embodiments, a and x may be as set forth above.

[0168] In some embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) polymer will be a linear copolymer having the formula:where each x is an integer from about 2 to about 50. In some embodiments, x is from about 1 to about 10. In various other embodiments, x may be as set forth above.

[0169] In other embodiments, the multi-functional alcohol initiator used will result copolymer having a star shaped configuration with three or more PAGES chains (arms) emanating outward from a core structure. In various embodiments, these star-shaped PAGES co polymers of the present invention may have 3, 4, 5, or 6 arms. While the star-shaped PAGES-based 3D printable copolymers of the present invention may in some embodiments have more than 6 arms, this is notpreferred as it may create additional difficulties with crosslinking the polymer. In some embodiments, the star-shaped PAGES-based co polymers of the present invention will have 3 arms. In other embodiments, the star-shaped PAGES-based co polymers of the present invention will have 4 arms. In other embodiments, the star-shaped PAGES-based co polymers of the present invention will have 5 arms. In still other embodiments, the star-shaped PAGES-based co polymers of the present invention will have 6 arms.

[0170] As will be apparent, the central core structure in these copolymers will comprise the residue of the multi-functional alcohol initiators used to form them. By way of example, the terms “3 -arm star” and “3 -arm star-shaped” refer to PAGES copolymers with 3 arms derived from the ROCOP of succinic anhydride and allyl giycidyl ether initiated by an alcohol having three available hydroxyl groups, such as glycerin, 2-hydroxymethyl-l,3-propanediol, 1,1,1- tris(hydroxymethyl)ethane, or 1,1,1 -Tri s(hydroxymethyl) propane, with three hydroxyl groups initiating ROCOP of one arm of the 3 -arm star polymer and the remainder of the alcohol molecule forming the core. Similarly, in one or more embodiments, the terms “4-arm star” and “4-arm star- shaped” are used to refer to PAGES copolymers with 4 arms derived from the ROCOP of succinic anhydride and allyl giycidyl ether initiated by an alcohol having four available hydroxyl groups, such as meso-erythritol, pentaerythritol, or (2R,3R)-butane-1,2,3,4-tetrol, with each of the four hydroxyl groups initiating ROCOP of one arm of the 4-arm star polymer and the remainder of the alcohol molecule forming the core. As follows, the terms “5-arm star” and “5-arm star-shaped” refer to PAGES copolymers with 5 arms derived from the ROCOP of succinic anhydride and allyl giycidyl ether initiated by an alcohol having five available hydroxyl groups, such as adonitol, arabitol, (2R,3r,4S)-pentane-1,2,3,4,5-pentol, or fucitol, with five hydroxyl groups initiating ROCOP of one arm of the 5-arm star polymer and the remainder of the al cohol molecule forming the core. Similarly, the terms “6-arm star” and “6-arm star-shaped” refer to PAGES copolymers with 6 arms derived from the ROCOP of succinic anhydride and allyl glycidyl ether initiated by an alcohol having six available hydroxyl groups, such aass hexakis[p- (hydroxymethyl)phenoxy]cyclotriphosphazene or dipentaerithyriol (dipenta), with six hydroxyl groups initiating ROCOP of one arm of the 6-arm star polymer and the remainder of the alcohol molecule forming the core. hexakis[p-(hydroxymethyl)phenoxy]cyclotriphosphazene or dipentaerithyriol (dipenta).

[0171] In some other embodiments, the poly(allyl glycidyl ether succinate) (“PAGES”) polymer will be a star copolymer having the general formula:where n is the number of arms connected to the core structure and the core structure comprises the residue of the multi-functionalized alcohol initiator used to form the polymer. In various embodiments, each x may be as set forth above.

[0172] As will be understood by those of skill in the art, the degradation temperature (Ta) of a polymer or copolymer is the temperature at which a material starts to experience irreversible thermal degradation. In various embodiments, the linear or star-shaped 3D printable PAGES copolymers used to form the solvent free 3D printable resins of the present invention will have a degradation temperature (Ta) of from about 250 °C to about 320 °C, as determined by Thermogravimetric Analysis (TGA) at 10% mass loss. . In some embodiments, the linear or star- shaped 3D printable PAGES copolymers will have a degradation temperature (Ta) of from about 250 °C to about 310 °C, in other embodiments, from about 260 °C to about 310 °C, in other embodiments, from about 270 °C to about 310 °C, in other embodiments, from about 280 °C to about 310 °C, in other embodiments, from about 290 °C to about 310 °C, in other embodiments, from about 300 °C to about 310 °C, in other embodiments, from about 250 °C to about 300 °C, in other embodiments, from about 250 °C to about 290 °C, in other embodiments, from about 250 °C to about 280 °C, in other embodiments, from about 250 °C to about 270 °C, and in other embodiments, from about 250 °C to about 260 °C, as determined by Thermogravimetric Analysis (TGA). Here, as well as elsewhere in the specification and claims, individual range values can be combined to form additional non-disclosed ranges

[0173] In various embodiments, the linear or star-shaped 3D printable PAGES copolymers used to form the solvent free 3D printable resins of the present invention will have a glass transition temperature (Tg) of from about -50 °C to about -10 °C as determined by DSC. As will be appreciated, the glass transition temperature (Tg) was determined as the midpoint of the transition in the second heating cycle. In some embodiments, the linear- or star-shaped 3D printable PAGEScopolymers will have a glass transition temperature (Tg) of from about -50 °C to about -10 °C, in other embodiments, from about -50 °C to about -20 °C, in other embodiments, from about -50 °C to about -30 °C, in other embodiments, from about -50 °C to about -40 °C, in other embodiments, from about -40 °C to about -10 °C, in other embodiments, from about -30 °C to about -10 °C, in other embodiments, from about -20 °C to about -10 °C, as determined by DSC. Here, as well as elsewhere in the specification and claims, individual range values can be combined to form additional non-disclosed ranges.

[0174] In a second aspect, the present invention involves methods for making the PAGES polymers described above. In various embodiments, substantially linear PAGES copolymers of the present invention may be synthesized as shown in Scheme 1, below.where a is an integer from about 2 to about 20 and x is an integer from about 1 to about 50.

[0175] The initiating alcohol forming the core of the linear 3D printable PAGES copolymers of the present invention is not particularly limited provided that it has two available hydroxyl functional groups and is capable of initiating ROCOP of succinic anhydride with allyl glycidyl ether in the presence of Mg(BHT)2(THF)2 or another magnesium catalyst. Suitable bi- functional alcohol initiators may include, without limitation, 1,2.-ethanediol, 1,3-propane diol, 1,4-butane diol, 1,5-pentane diol, 1 ,6-hexanediol, 1 ,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,1.1- undecanediol, 1 , 12-dodecanediol, 1 , 13 -tridecan ediol, 1 , 14-tetradecanediol, 1 , 15-pentadecanediol, 1,16-hexadecanediol, 1,17-heptadecanediol, 1,18-octadecanediol, 1,19-nonadecanediol, 1,20- icosanediol, and combinations thereof.

[0176] As set forth above, in embodiments where the PAGES copolymer is to be star shaped, the copolymers are synthesized through a core-first process using a or multi-functional alcohol as initiator, and a magnesium catalyst such as Mg(BHT)2(THF)2 as catalyst for controlled ROCOP of succinic anhydride with allyl glycidyl ether. The initiating alcohol forming the core of the star- shaped 3D printable PAGES copolymers of the present invention is not particularly limited provided that it has three or more available hydroxyl functional groups and is capable of initiating ROCOP of succinic anhydride with allyl glycidyl ether, in the presence of Mg(BHT)2(THF)2.

[0177] In some embodiments, a 1 : 1 ratio of allyl glycidyl ether to succinic anhydride may be used. Unfortunately, however, if a 1: 1 ratio of allyl glycidyl ether and succinic anhydride is used it will cause the end group of the chain to be statistically determined resulting in changes to viscosity because any end groups resulting from the succinic anhydride monomer would be capable of hydrogen bonding, thereby increasing the viscosity of the polymer. Accordingly, it is preferable that a slight excess of allyl glycidyl ether is used ensure that all end groups result from the allyl glycidyl ether and thus cannot hydrogen bond. In some embodiments, the ratio of allyl glycidyl ether and succinic anhydride will be at least 1.01:1. In various embodiments, the ratio of allyl glycidyl ether to succinic anhydride will be from 1: 1 to 1. 1 : 1

[0178] In some embodiments, the star-shaped 3D printable PAGES copolymers of the present invention may be formed using multi-functional initiators as shown in Schemes 2 and 3, below.where x is an integer from about 5 to about 50 and the core structure is the residue of the multi- functional glycerin initiator used to form the polymer.where x is an integer from about 5 to about 30 and the core structure is the residue of the multi- functional erythritol initiator used to form the polymer.

[0179] Suitable multi-functional alcohol initiators, may include, without limitation, glycerol (propane- 1,2, 3 -triol), meso-erythritol ((2R ,3S)-butane-1,2,3,4-tetrol), pentaerythritol (2,2- bis(hydroxymethyl)propane- 1,3 -diol), theitol ((2R ,3R)-butane-1,2,3,4-tetrol), arabitol ((2R ,4R )- pentane-1,2,3,4,5-pentol) xylitol ((2R ,3R,4S)-pentane-1,2,3,4,5-pentol), adonitol ((2R ,3s,4S)- pentane-1,2,3,4,5-pentol), fucitol ((2R ,3S,4R ,5S)-hexane-1,2,3,4,5-pentol), sorbitol ((2S,3R,4R,5R)-hexane-1,2,3,4,5,6-hexol), dulcitol ((2R ,3S,4R ,5S)-hexane-1,2,3,4,5,6-hexol), mannitol (hexane-1,2,3,4,5,6-hexol) Iditol ((2R ,3S,4S,5R )-Hexane-1,2,3,4,5,6-hexol), inositol (1R ,25,3r,4R ,5S,6s)-cyclohexane-1,2,3,4,5,6-hexol), and voiemitol ((2R ,3R ,5R ,6R )-heptane- 1,2,3,4,5,6,7-heptol), and combinations thereof. In some embodiments, the multi-functional alcohol initiator may be a sugar based alcohol. In one or more embodiments, the multi-functional alcohol initiator may be selected from the family of sugar based alcohols that includes meso- erythritol and adonitol.

[0180] In a third aspect, the present invention is directed to reduced solvent or, preferably, solvent free 3D printable resins. As set forth above, it has been found that mono-, bi-, or multi- functional alcohol molecules can be used to initiate of ROCOP of succinic anhydride and allyl glycidyl ether in the presence of a Mg(BHT)2(THF)2 catalyst, thereby forming linear and star- shaped PAGES-based 3 D printable copolymers of the present invention. As set forth above, inembodiments where the PAGES copolymer is to be substantially linear, a core-first process initiated by a bifunctional alcohol initiator is used.

[0181] In various embodiments, a selected PAGES polymer is synthesized as set forth above and combined with a bi or multifunctional thiol crosslinker, as described above. As will be apparent, the thiol functional groups on these crosslinkers will react with the allyl groups on the PAGES copolymers in the to crosslink the polymer during 3D printing via thiol-ene click chemistry.

[0182] In some embodiments, the PAGES copolymers used to form solvent free 3D printable resins, will typically have a neat complex viscosity of from about 0.5 Pa.s to about 15 Pa.s, preferably from about 0.5 Pa.s to about 12 Pa.s, and more preferably from about 0.5 Pa.s to about 10 Pa.s and a degree of polymerization from about 2 to about 20, preferably from about 3 to about 12, and more preferably from about 6 to about 9.

[0183] In some embodiments, the PAGES copolymers used to form solvent free 3D printable resins is a linear copolymer having the formula:where R is a residue of a mono-functional initiating alcohol and x is an integer from 2 to 20.

[0184] In some other embodiments, the PAGES copolymers used to form solvent free 3D printable resins is a linear copolymer having the formula:where a is an integer from 2 to 20 and each x is an integer from about 1 to about 10.

[0185] In some other embodiments, the PAGES copolymers used to form solvent free 3D printable resins is a linear copolymer having the formula:where a is an integer from 2 to 20 and each x is an integer from about 1 to about 10.

[0186] The amount of bi or multifunctional thiol crosslinker will depend both the crosslink ratio used as well as the molecular weight of the thiol crosslinker. In one or more embodiments, the ratio of allyl groups on the PAGES polymer to thiol groups on the multifunctional thiol crosslinker will be from about 1:1 to about 60: 1. In some embodiments, the ratio of allyl groups on the PAGES polymer to thiol groups on the multifunctional thiol crosslinker will be from about 1 : 1 to about 50: 1, in other embodiments, from about 1 : 1 to about 30: 1, in other embodiments, from about 1 : 1 to about 1 :20, in other embodiments, from about 1 : 1 to about 1 : 10, in other embodiments, from about 1:5 to about 60:1, in other embodiments, from about 15:1 to about 60:1, in other embodiments, from about 25:1 to about 60:1, in other embodiments, from about 35:1 to about 60: 1, and in other embodiments, from about 45: 1 to about 60: 1. Here, as well as elsewhere in the specification and claims, individual range values can be combined to form additional non- disclosed ranges. In some embodiments, the ratio (wt. / wt.) of allyl groups on the PAGES polymer to thiol groups on the multifunctional thiol crosslinker will be about 5:1.

[0187] The bi- or multi-functional thiol crosslinker is not particularly limited and any molecul e having two or more available thiol groups may be used provided that the compound does not otherwise interfere with the reaction or reagents being used. In some embodiments, the bi- or multi-functional thiol crosslinker is trimethylolpropane tris (3 -mercaptopropionate), bis(3-mercaptopropyl) succinate, pentaerythritol tetrakis(3-mercaptopropionate), isosorbide bis(3- mercaptopropionate), 2,2’-((diisopropylsilanediyl)bis(oxy))bis(ethane-l-thiol) or a combination thereof. In some of these embodiments, the bi- or multi-functional thiol crosslinker is trimethylolpropane tris (3-mercaptopropionate). In some embodiments, the bi- or multi-functional thiol crosslinker will have the formula:

[0188] As set forth above, the amount of bi- or multi-functional thiol crosslinker used will depend upon both the crosslink ratio used as well as the molecular weight of the thiol crosslinker. In various embodiments, the bi- or multi-functional thiol crosslinker will comprise from about 0.1 mol.% to about 10 mol.% of the solvent free 3D printable resin. In some embodiments, the bi- or multi-functional thiol crosslinker will comprise from about 0.5 mol.% to about 10 mol.% , in other embodiments, from about 1 mol.% to about 10 mol.%, in other embodiments, from about 2 mol.% to about 10 mol.%, in other embodiments, from about 4 mol.% to about 10 mol.%, in other embodiments, from about 6 mol.% to about 10 mol.%, in other embodiments, from about 8 mol.% to about 10 mol.%, in other embodiments, from about 0.1 mol.% to about 9 mol.%, in other embodiments, from about 0.1 mol.% to about 7 mol.%, in other embodiments, from about 0.1 mol.% to about 5 mol.%, and in other embodiments, from about 0.1 mol.% to about 3 mol.% of the solvent free 3D printable resin.

[0189] In various embodiments, the bi- or multi-functional thiol crosslinker will comprise from about 1 wt.% to about 36 mol.% of the solvent free 3D printable resin. In some embodiments, the bi- or multi-functional thiol crosslinker will comprise from about 1 wt.% to about 30 wt.% , in other embodiments, from about I wt.% to about 20 wt.%, in other embodiments, from about I mol.% to about 10 wt.%, in other embodiments, from about 2 wt.% to about 36 wt.%, in other embodiments, from about 4 wt.% to about 36 wt.%, in other embodiments, from about 8 wt.% to about 36 wt.%, in other embodiments, from about 15 wt.% to about 36 wt.%, in other embodiments, from about 20 wt.% to about 36 wt.%, in other embodiments, from about 26 wt.%to about 36 wt.%, and in other embodiments, from about 30 wt.% to about 36 wt.% of the low solvent or solvent free 3D printable resin.

[0190] In one or more embodiments, the solvent free 3D printable resins of the present invention will also contain a photoinhibitor or light attenuating agent to absorb light to prevent excess radical formation, thus helping to suppress unintended reactions. Suitable photoinhibitors or light attenuating agents include, without limitation, oxybenzone (HMB), 2,2,6,6-tetramethyl-l- piperidinyloxy (TEMPO), quinolone yellow, Sudan I, Sudan II, sudan III, avobenzone, or a combination thereof. In ssoommee embodiments, the photoinitiator phenylbi s-(2, 4,6- trimethylbenzoyl)phosphine oxide (BAPO) is used in combination with the photoinhibitor oxybenzone (HMB) to help initiate and control radical formation to prevent lateral overcuring. In some embodiments, the photoinhibitor may be 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO). In some other of these embodiments, the photoinhibitors oxybenzone (HMB) and 2, 2,6,6- tetramethyl-l-piperidinyloxy (TEMPO) are both used to control radical formation to prevent lateral overcuring. In addition, photoinhibitors are added to the polymer prior to addition of the multi-functional thiol crosslinkers to prevent spontaneous crosslinking. In some of these embodiments, the solvent free 3D printable resins of the present invention will contain about 0.01 wt.% TEMPO.

[0191] As will be understood by those of skill in the art, the term “overcuring” refers to the curing of liquid resin into solid in locations adjacent to IJV light exposure. It indicates a lack of control over the crosslinking process and can cause low resolution printing. As follows, the term “lateral overcuring” refers to overcuring that happens in the XY plane along the cross section of the printed layer, whereas the term “vertical overcuring” refers to overcuring that happens along the Z axis.

[0192] In one or more embodiments, the solvent free 3D printable resins of the present invention will contain from about 0.01 wt. % to about 3 wt. % of a photoinhibitor or light attenuating agent, as described above. In some embodiments, the solvent free 3D printable resins of the present invention will contain 0.01 wt.% TEMPO.

[0193] As set forth above, in some embodiments, the solvent free 3D printable resins of the present invention will further comprise an operative amount of at least one photoinitiator. The photoinitiators that may be used in the solvent free 3-D printable resin of the present invention are not particularly limited and may be any photoinitiator capable of producing a radical whenirradiated with electromagnetic radiation at a suitable wavelength (approximately 254-450 nm), which does not otherwise react with any other material in the resin or quench the reaction. As will be appreciated by those of skill in the art, the choice of photoinitiator is often dictated by the requirements of the 3D printer being used, but suitable photoinitiators may include, without limitation, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), IRGACURE™ 819 and IRGACURE™ 784 (BASF, Ludwigshafen, Germany), IRGACURE™ 819 / BAPO (BASF, Florham Park, NJ), IRGACURE™ 2959 (BASF, Florham Park, NJ), lithium acylphosphinate (LAP), and combinations thereof.

[0194] The amount of photoinitiator required will depend upon the photoinitiator being used. In one or more embodiments, the solvent free 3D printable resins of the present invention will contain from about 0.5 wt. % to about 3 wt. % photoinitiator. In some of these embodiments, the solvent free 3D printable resins of the present invention will contain from about 0.5 wt. % to about 3 wt. % phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO). In some embodiments, the solvent free 3D printable resins of the present invention will contain 0.5 wt.% BAPO.

[0195] In various embodiments, the solvent free 3D printable resins of the present invention may also contain one or more other additives commonly used in 3D printable resins such as dyes, light attenuating agents, dispersants, emulsifiers, ceramics, BIOGLASS™, hydroxyapatite, 0- tricalcium phosphate, radical scavengers, or combinations thereof.

[0196] The dyes that may be used in the 3-D printable resin of embodiments of the present invention are not particularly limited and may include any dye conventionally used in 3D printing, provided that it does not quench the radical s necessary for crosslinking. Suitable dyes may include, without limitation, Sudan I dye, Sudan II dye, Sudan IB, dye, and combinations thereof. In some embodiments, Sudan I dye may be used. In one or more embodiments, the solvent free 3D printable resins of the present invention will contain from about 0.01 wt. % to about 3 wt. % dye. hi one or more embodiments, the solvent free 3D printable resins of the present invention will contain about 0.04 wt. % dye.

[0197] Emulsifiers that may be used in the 3-D printable resin of embodiments of the present invention are not particularly limited and may include, without limitation, sucrose, trehalose, or any sugar molecule. In various embodiments, the various resin components and additives described above may be added to the 3-D printable resin at any time prior to crosslinking of the PPF polymer, as described below.

[0198] In various embodiments, the bi- or multi-functional thiol crosslinker will comprise from about 0.1 mol.% to about 10 mol.% of the solvent free 3D printable resin, hi some embodiments, the bi- or multi-functional thiol crosslinker will comprise from about 0.5 mol.% to about 10 mol.% , in other embodiments, from about 1 mol.% to about 10 mol.%, in other embodiments, from about 2 mol.% to about 10 mol.%, in other embodiments, from about 4 mol.% to about 10 mol.%, in other embodiments, from about 6 mol.% to about 10 mol.%, in other embodiments, from about 8 mol.% to about 10 mol.%, in other embodiments, from about 0.1 mol.% to about 9 mol.%, in other embodiments, from about 0.1 mol.% to about 7 mol.%, in other embodiments, from about 0.1 mol.% to about 5 mol.%, and in other embodiments, from about 0.1 mol.% to about 3 mol.% of the solvent free 3D printable resin.

[0199] As will be understood by those of skill in the art, the complex viscosity (q ) of a polymer or copolymer is a measurement of a its total resistance to flow. Advantageously, it has been found that the solvent free 3D printable resins of the present invention have a complex viscosity that is suitable for 3D printing, without the need for a solvent or other diluent. In some embodiments, these solvent free 3D printable resins have a complex viscosity of from about 0.5 Pa.s to about 20 Pa.s, in other embodiments, from about 0.5 Pa.s to about 15 Pa.s, in other embodiments, from about 0.5 Pa.s to about 10 Pa.s, in other embodiments, from about 0.5 Pa.s to about 5 Pa.s, in other embodiments, from about 1 Pa.s to about 20 Pa.s, in other embodiments, from about 5 Pa- s to about 20 Pa- s, in other embodiments, from about 10 Pa.s to about 20 Pa- s, in other embodiments, from about 15 Pa- s to about 20 Pa- s. In some embodiments, these solvent free 3D printable resins have a complex viscosity from about 3 Pa.s to about 10 Pa.s.

[0200] In one or more embodiments, the solvent-free poly(allyl glycidyl ether succinate) resins of the present invention will comprise from 80 wt.% to about 99 wt.% linear poly(allyl glycidyl ether succinate) polymer, from 9 wt.% to about 11 wt.% multi-functional thiol crosslinker, 0.5 wt.% BAPO and 0.01 wt.% TEMPO, and have a crosslink ratio of from about 1:1 to about 15:1. In some embodiments, the solvent-free resin comprises from about 80 wt.% to about 99 wt.% of said poly(allyl glycidyl ether succinate) copolymer; from to 1 wt.% to about 20 wt.% of said multi-functional thiol crosslinker, wherein the molar ratio of allyl groups in said poly(allyl glycidyl ether succinate) copolymer to thiol groups in said multi-functional thiol crosslinker is from about 1 : 1 to about 20: 1 ; and from about 0.1 wt.% to about 3 wt.% of a photoinitiator.

[0201] In embodiments where the selected PAGES polymer has a complex viscosity over 20 Pa.s, a solvent or reactive diluent may be added produce a low solvent poly(allyl glycidyl ether succinate) resin having a complex viscosity of from about 0.5 Pa.s to about 20.0 Pa.s. Suitable solvents or reactive diluents may include, without limitation, ethyl acetate, chloroform, acetone, methyl ethyl ketone, ethanol, dimethyl sulfoxide (DMSO) and combinations thereof. In various embodiments, solvent or reactive diluent will be from about 0% (not present) to about 20% of the low solvent poly(allyl glycidyl ether succinate) resin. As will be apparent, no solvent or reactive diluent is added to the solvent-free poly(allyl glycidyl ether succinate) resins for the purpose of controlling the complex viscosity of the resin, although there may be small amounts (less than 1 wt.% as verified through mass loss in thermogravimetric analysis (TGA)) of solvents present in the resin, that are introduced during the polymer synthesis which uses toluene as a solvent.

[0202] In one or more embodiments, the low solvent poly(allyl glycidyl ether succinate) resins of the present invention will comprise from 0 to 20 wt.% ethyl acetate, 0.6 wt.% BAPO and 0.4 wt.%) HMB.

[0203] In various embodiments, the solvent free 3D printable resins of the present invention will have a degradation temperature (Td) of from about 250 °C to about 320 °C, as determined by Thermogravimetric Analysis (TGA). In some embodiments, the solvent free 3D printable resins will have a degradation temperature (Td) of from about 260 °C to about 310 °C, in other embodiments, from about 270 °C to about 310 °C, in other embodiments, from about 280 °C to about 310 °C, in other embodiments, from about 290 °C to about 310 °C, in other embodiments, from about 300 °C to about 310 °C, in other embodiments, from about 250 °C to about 300 °C, in other embodiments, from about 250 °C to about 290 °C, in other embodiments, from about 250 °C to about 285°C, in other embodiments, from about 250 °C to about 280 °C, in other embodiments, from about 250 °C to about 270 °C, in other embodiments, from about 250 °C to about 260 °C, as determined by Thermogravimetric Analysis (TGA).

[0204] In various embodiments, the solvent free 3D printable resins of the present invention will have a glass transition temperature (Tg) of from about -50 °C to about -10 °C as determined by Differential Scanning Calorimetry (DSC). The glass transition temperature (Tg) was determined as the midpoint of the transition in the second heating cycle In some embodiments, the solvent free 3D printable resins will have a glass transition temperature (Tg) of from about -40 °C to about -10 °C, in other embodiments, from about -30 °C to about -10 °C, in other embodiments, from about-20 °C to about -10 °C, in other embodiments, from about -50 °C to about -20 °C, in other embodiments, from about -50 °C to about -30 °C, and in other embodiments, from about -50 °C to about -40 °C. as determined by DSC.

[0205] In a fourth aspect, the present invention is directed to methods for making the reduced solvent or, preferably, solvent free 3D printable resins described above. The method begins with preparation of a poly(allyl glycidyl ether succinate) (PAGES) copolymer, as set forth above. In various embodiments, the PAGES copolymer will have a degree of polymerization of from about 2 to about 50 and a complex viscosity of from about 0.5 Pa.s to about 20.0 Pa.s, preferably from about 0.5 Pa.s to about 15 Pa.s, and more preferably, from about 0.5 Pa.s to about 10 Pa.s. In embodiments where a PAGES copolymer has a complex viscosity that even when diluted by the multi-functional thiol crosslinker is too high to permit efficient 3D printing, a sol vent / ' diluent may be added. These embodiments, while not preferred, permit 3D printing of higher molecular weight polymers with different mechanical and degradation properties using far less diluent than would ordinarily be required by conventional 3D printable polymers.

[0206] As set forth above, the term “polymer resin composition” is used herein to refer to the portion of the reduced solvent or, preferably, solvent free 3D printable resin comprising the PAGES copolymers, diluent (if any), exclusi ve of the multifunctional thiol crosslinkers and other components such as photoinhibitors, photoinitiators, and other additives. In various embodiments, the PAGES copolymers will comprise from about 80 wt.% to more than 99 wt.% (99+ wt.%) of the polymer resin composition. In some of these embodiments, the PAGES copolymers will comprise more than about 85 wt.% of the polymer resin composition. In some of these embodiments, the PAGES copolymers will comprise more than about 90 wt.% of the polymer resin composition. In some of these embodiments, the PAGES copolymers will comprise more than about 95 wt.% of the polymer resin composition. As set forth above, polymer resin composition for the solvent free PAGES copolymer resins according to the present invention will contain 99 wt.% or more PAGES copolymer.

[0207] Once the PAGES polymer is chosen and, if necessary, diluted to a 3D printable viscosity. One or more photoinhibitor or light attenuating agent, as described above, is added to the PAGES polymer and the mixture is stirred. It is often important, depending upon the PAGES copolymer and multi-functional crosslinker being used, that a photoinhibitor is added to the polymer before the multi-functional crosslinker is added to prevent premature crosslinking and, asset forth above, lateral overcuring. The photoinhibitor effectively prevents crosslinking until it can be initiated by the photoinitiator during the 3D printing process. In various embodiments, the PAGES copolymer / photoinhibitor mixture is mixed by conventional means to distribute the photoinhibitor throughout the PAGES copolymer.

[0208] The other components (i.e., the multi-functional thiol crosslinker, photoinitiator, dye, and other additives) of the resin are next added to the PAGES copolymer / photoinhibitor mixture. In various embodiments, an operative amount of one or more photoinitiators as described above are added to the PAGES copolymer / photoinhibitor mixture. As will be understood, the photoinitiator will produce radicals to initiate the crosslinking reaction when acted upon by the 3D printing apparatus. The photoinitiators that may be used in the low solvent and solvent free 3-D printable resin of the present invention are not particularly limited and may be any photoinitiator capable of producing a radical when irradiated with electromagnetic radiation at a suitable wavelength (approximately 254-450 nm), which does not otherwise react with any other material in the resin or quench the reaction. As will be appreciated, the type of photoinitiator used will depend upon the operation of the 3D printing apparatus and the requirements of the 3D printing apparatus should be considered when selecting a suitable photoinitiator. In one or more embodiments, the photoinitiator will initiate crosslinking when irradiated with ultra-violet (UV) light. Suitable crosslinkers may include, without limitation, phenylbis(2,4,6- trimethylbenzoyl)phosphine oxide (BAPO), IRGACURE™ 819 and IRGACURE™ 784 (BASF, Ludwigshafen, Germany), IRGACURE™ 819 / BAPO (BASF, Florham Park, NJ), IRGACURE™ 2959 (BASF, Florham Park, NJ), lithium acylphosphinate (LAP), and combinations thereof.

[0209] In one or more embodiments, one or more dye may also be added to the low solvent and solvent free 3-D printable resin of the present invention. In some embodiments, the dye serves as an opaqueing agent to prevent, or at least limit, transmission of the UV light through the resin during printing. In some other embodiments, the dye is used to produce colored 3D printed parts. As set forth above, he dyes that may be used in the 3-D printable resin of embodiments of the present invention are not particularly limited and may include any dye conventionally used in 3D printing, provided that it does not quench the radicals necessary for crosslinking. Suitable dyes may include, without limitation, Sudan I dye, Sudan II dye, Sudan III, dye, and combinations thereof. In some embodiments, Sudan I dye may be used. In one or more embodiments, the solvent free 3D printable resins of the present invention will contain from about 0.01 wt. % to about 3 wt.% dye. In one or more embodiments, the solvent free 3D printable resins of the present invention will contain about 0.04 wt. % dye.

[0210] In one or more embodiments, one or more emulsifier may also be added to the low solvent and solvent free 3-D printable resin of the present invention. Emulsifiers that may be used in the 3-D printable resin of embodiments of the present invention are not particularly limited and may include, without limitation, sucrose, trehalose, or any sugar molecule. In various embodiments, the various resin components and additives described above may be added to the 3- D printable resin at any time prior to crosslinking of the PPF polymer, as described below.

[0211] In various embodiments, other additives commonly used in 3D printing applications such as dispersants, ceramics, BIOGLASS1M, hydroxyapatite, P-tricalcium phosphate, radical scavengers, or combinations thereof may also be added to the low solvent or solvent free 3D printable resins of the present invention.

[0212] Finally, one or more bi- or multi-functional thiol crosslinker, as described above, is added to the resin. As set forth above, the bi- or multi-functional thiol crosslinker is not particularly limited and any molecule having two or more available thiol groups may be used provided that the compound does not otherwise interfere with the reaction or reagents being used. In some embodiments, the bi- or multi-functional thiol crosslinker is tri methylol propane tris (3- mercaptopropionate), bi s(3 -mercaptopropyl) succinate, pentaerythritol tetrakis(3- mercaptopropionate), isosorbide bi s(3 -mercaptopropionate), 2,2’-((diisopropylsilanediyl)bis(oxy))bis(ethane-l-thiol) or a combination thereof. In some of these embodiments, the bi- or multi-functional thiol crosslinker is trimethylolpropane tris (3- mercaptopropionate). In some embodiments, the bi- or multi-functional thiol crosslinker will have the formula:As set forth above, the amount of bi- or multi-functional thiol crosslinker used will depend upon both the crosslink ratio used as well as the molecular weight of the thiol crosslinker.

[0213] As will be apparent, the amount of the bi- or multi-functional thiol crosslinker added to the resin will depend upon the desired crosslink ratio. As used herein, the terms “crosslink ratio” or “crosslinking ratio” are used interchangeably to refer to the molar ratio of allyl groups in said linear poly(allyl glycidyl ether succinate) copolymer to thiol groups in said multi-functional thiol crosslinker. In various embodiments, the 3D printed polymer structure formed from the solvent free 3D printable resins described above will have a crosslink ratio (alkene to thiol) of from about 1 : 1 to about 60: 1 . In some embodiments, the 3D printed polymer structure formed from the solvent free 3D printable resins described above will have a crosslink ratio of from about 1 : 1 to about 40: 1 , in other embodiments, from about 1 : 1 to about 30: 1, in other embodiments, from about 1 : 1 to about 1:20, in other embodiments, from about 1:1 to about 1:10, in other embodiments, from about 1:5 to about 60:1, in other embodiments, from about 15: 1 to about 60:1, in other embodiments, from about 25:1 to about 60:1, in other embodiments, from about 35:1 to about 60: 1, and in other embodiments, from about 45:1 to about 60:1. In some embodiments, the 3D printed polymer structure formed from the solvent free 3D printable resins described above will have a crosslink ratio of from about 1:1 to about 20:1. In some embodiments, the 3D printed polymer structure formed from the solvent free 3D printable resins described above will have a crosslink ratio of 5: 1.

[0214] In various embodiments, the bi- or multi-functional thiol crosslinker added will comprise from about 0.1 mol.% to about 10 mol.% of the solvent free 3D printable resin. In some embodiments, the bi- or multi-functional thiol crosslinker added will comprise from about 0.5 mol.% to about 10 mol.%, in other embodiments, from about 1 mol.% to about 10 mol.%, in other embodiments, from about 2 mol.% to about 10 mol.%, in other embodiments, from about 4 mol.% to about 10 mol.%, in other embodiments, from about 6 mol.% to about 10 mol.%, in other embodiments, from about 8 mol.% to about 10 mol.%, in other embodiments, from about 0.1 mol.% to about 9 mol.%, in other embodiments, from about 0.1 mol.% to about 7 mol.%, in other embodiments, from about 0.1 mol.% to about 5 mol.%, and in other embodiments, from about 0.1 mol.% to about 3 mol.% of the solvent free 3D printable resin.

[0215] In various embodiments, the bi- or multi-functional thiol crosslinker added will comprise from about 1 wt.% to about 36 mol.% of the solvent free 3D printable resin. In some embodiments, the bi- or multi-functional thiol crosslinker will comprise from about 1 wt.% to about 30 wt.% , in other embodiments, from about 1 wt.% to about 20 wt.%, in other embodiments, from about 1 mol.% to about 10 wt.%, in other embodiments, from about 2 wt.% to about 36wt.%, in other embodiments, from about 4 wt.% to about 36 wt.%, in other embodiments, from about 8 wt.% to about 36 wt.%, in other embodiments, from about 15 wt.% to about 36 wt.%, in other embodiments, from about 20 wt.% to about 36 wt.%, in other embodiments, from about 26 wt.% to about 36 wt.%, and in other embodiments, from about 30 wt.% to about 36 wt.% of the low solvent or solvent free 3D printable resin.

[0216] Once these materials have been added to the polymer resin composition, the resulting mixture is stirred to ensure complete mixing of the various components to produce the low solvent or solvent free 3-D printable resin of the present invention.

[0217] In another aspect, the present invention is directed to a 3D printed polymer structure formed from the solvent free 3D printable resins described above. These 3D structures may be printed using any suitable light-based 3D printing system including but not limited to digital light processing (DLP) and stereolithography (SLA) 3D printers.

[0218] In various embodiments, the 3D printed polymer structure formed from the solvent free 3D printable resins described above will have a crosslink ratio (alkene to thiol) of from about 1 : 1 to about 60: 1. In some embodiments, the 3D printed polymer structure formed from the solvent free 3D printable resins described above will have a crosslink ratio of from about 1 : 1 to about 40: 1 , in other embodiments, from about 1 : 1 to about 30: 1, in other embodiments, from about 1 : 1 to about 1:20, in other embodiments, from about 1:1 to about 1:10, in other embodiments, from about 1:5 to about 60:1, in other embodiments, from about 15:1 to about 60:1, in other embodiments, from about 25:1 to about 60:1, in other embodiments, from about 35:1 to about 60: 1, and in other embodiments, from about 45:1 to about 60:1. In some embodiments, the 3D printed polymer structure formed from the solvent free 3D printable resins described above will have a crosslink ratio of 5: 1.

[0219] As shown in the Experimental section below, the mechanical and degradation properties of crosslinked materials were evaluated, and the results are displayed in FIGS. 22- 63B. Particularly important and surprising properties are shown in FIG. 49, which demonstrates that solvent free prints experience less shrinkage while having higher moduli than solvent containing prints.Experimental

[0220] To more fully illustrate and reduce the invention to practice, the solvent-free 3D printable PAGES polymers and polymer structures of the present invention were synthesized asset forth above and their printing performance, structure, and physical and chemical properties evaluated by Nuclear Magnetic Resonance (NMR) Spectroscopy (1H NMR); Size-Exclusion Chromatography (SEC); Matrix-Assisted Laser Desorption / Ionization Time of Flight Mass Spectrometry (MALDI TOF); Differential Scanning Calorimetry (DSC); Thermogravimetric Analysis (TGA); Rheology; Attenuated Total Reflection Fourier Transform Infrared (ATR FT1R) Spectroscopy; Uniaxial tensile testing; and Dynamic Mechanical Analysis (DMA). In addition, the swelling, degradation and shrinking properties of the solvent-free 3D printable PAGES polymers and polymer structures of the present invention were characterized and evaluated.Synthesis and Characterization of PAGES Polymer.

[0221] Poly(allyl glycidyl ether succinate) (PAGES) copolymers were synthesized using ring opening copolymerization (ROCOP) of allyl glycidyl ether and succinic anhydride using a Mg(BHT)2(THF)2 catalyst and 1,6-hexanediol as a difunctional initiator (See, FIG. 1). The kinetics of the PAGES polymerization are slower than ROCOP incorporating propylene oxide due to the sterically hindered epoxide. Analysis of the crude1H NMR samples taken at 24 hours intervals (FIG. 2) shows the appearance of resonances corresponding to the m ethylene (-CH2O-) protons in the polymer at 5 = 4.3 and δ = 3.6 ppm and the disappearance of methylylidene (-CH-) protons in the allyl glycidyl ether monomer at δ = 3.7, δ = 3.3, and δ = 3.1 ppm as expected throughout the polymerization process. Integrations of the δ = 4.3 ppm resonance of the polymer in comparison to the δ = 1.6 ppm resonance of the initiator reveal an initial slow conversion followed by an increased monomer consumption until slowing as the targeted DPnwas achieved at high conversion. A slow initiation occurs over 4 days attributed to two effects: low solubility of succinic anhydride in toluene at 80 °C and Mg(BHT)2(THF)2 catalyst bridging complexes. (See, e.g., Wattanasin, S. Succinic Anhydride. In Encyclopedia of Reagents for Organic Synthesis; John Wiley & Sons, Ltd, 2001. https: / / doi.org / 10.1002 / 047084289X.rsl25 and Calabrese, J.; Cushing, M. A. Jr.; Ittel, S. D. “Sterically Hindered Magnesium Aryloxides.” Inorg. Chem. 1988, 27 (5), 867-870. https: / / doi.org / T0.1021 / ic00278a023, the disclosure of which are incorporated herein by reference in their entirety). The Mg(BHT)?(THF)2 catalyst is hypothesized to form a stable, inactive bridging species that coordinates to both alcohol moieties of the diol initiator rather than complex to one alcohol initiator and one THF molecule, as expected in the coordination-insertion polymerization mechanism proposed for the ROCOP synthesis of PAGES. The polymerizationwill not occur until this complex decomposes. (See, Calabrese, J. et al. “Sterically Hindered Magnesium Aryloxides.” Inorg. Chem. 1988, 2.7 (5), 867-870. https: / / doi.org / 10.1021 / ic00278a023, the disclosure of which are incorporated herein by reference in their entirety).

[0222] For these experiments, a family of PAGES oligomers with controlled degree of polymerizations (DPn) was realized by stoichiometrically varying the monomer to initiator ratio. A reaction mechanism for the synthesis of PAGES using ring opening copolymerization of succinic anhydride and allyl glycidyl ether is shown in FIG. 1. FIG. IB is a schematic diagram showing 3D printing of PAGES oligomers with DPnof 6, 9 and 16 into tensile bars for mechanical property testing using digital light processing. As can be seen, network formation occurred through photochemically activated thiol-ene additions with a trifunctional thiol molecule.

[0223] Through integration of alkyl proton (-CH2-) resonances in the hexanediol initiator (8 = 1.6 ppm) and methylene (-CHzO(C=O)-) protons in the polymer repeat unit (δ = 4.3 ppm), three individual DPnwere verified (DPn: 6, 9, and 16) (FIGS. 3-6). Size exclusion chromatography (SEC) (FIG. 7) and matrix-assisted laser desorption ionization time-of-flight (MALDI TOF) mass spectrometry (FIGS. 8D-F, Table 1) each reported monomodal distributions for both DP6and DP9 oligomers, indicating that a narrow' molecular mass distribution was achieved.

[0224] Additionally, the mass of the repeat unit (214 g mol-1) was confirmed viaMALDITOF mass spectrometry (see, FIGS. 9A-F) to show a single population with well-defined end groups. The polymer copolymerization sequence was further confirmed by 2D NMR spectroscopy (FIGS. 10, 11).

[0225] Each oligomer was characterized thermally to determine the degradation temperature (Td,10%) and the glass transition temperature (Tg) (see, Table 2).Thermogravimetric analysis indicated that all oligomers were thermally stabile with degradation temperatures over 300 °C (FIG. 12). (See, e.g., Terzopoulou, Z. et al., “Thermal Degradation of Biobased Polyesters: Kinetics and Decomposition Mechanism of Polyesters from 2,5- Furandicarboxylic Acid and Long-Chain Aliphatic Diols.” Journal of Analytical and Applied Pyrolysis 2016, 117, 162-175. https: / / doi.org / 10.1016 / j.jaap.2015.11.016, the disclosure of which is incorporated herein by reference in its entirety). Differential scanning calorimetry (DSC) noted Tgvalues between -45 and -39 °C for each of the oligomers (FIG. 13) indicating that this family of oligomers would exhibit relatively low viscosities at ambient temperature. (See, e.g., Luo, ¥.; Dolder, C. K.; Walker, J. M.; Mishra, R.; Dean, D.; Becker, M. L. “Synthesis and Biological Evaluation of Well-Defined Poly(Propylene Fumarate) Oligomers and Their Use in 3D Printed Scaffolds.” Biomacromolecules 2016, 17 (2), 690-697. https: / / doi.org / 10.1021 / acs.biomac.6b00014, the disclosure of which is incorporated herein by reference in its entirety). Additionally, no melt transition temperatures or crystallization enthalpies were observed in the DSC thermograms, indicating that PAGES oligomers are completely amorphous due to the lack of stereoregularity of the pendent groups.

[0226] Rheological measurements helped assess the viscosity of PAGES solutions as resins for reduced solvent and solvent free DLP 3D printing. Frequency sweeps at ambient temperature were performed on each neat oligomer as well as a series of formulations diluted in ethyl acetate (95, 90, 80, and 70 wt.%) (FIGS. 8A-C). A linear relationship between DPnand viscosity of each neat polymer was determined (TIGS. 14A-B), as each integer unit increase in DPnresults in an approximately -4.2 Pa.s (-4200 cP) increase in viscosity. This relationship can be utilized to synthesize oligomers with specific viscosity values through targeting the corresponding DPn.3D Printing

[0227] As set forth above, using the minimum amount of solvent to achieve the desired printable resin viscosity is ideal to minimize the negative impacts associated with part shrinkage and residual stress. Each of the resins were formulated to contain PAGES, the diluent ethyl acetate, a photo initiator, a photo inhibitor, and a trifunctional small-molecule thiol crosslinker trimethylolpropane tris (3 -mercaptopropionate). The photoinitiator phenylbis-(2,4,6- trimethylbenzoyl)phosphine oxide (BAPO) and photo inhibitors oxybenzone (HMB) and 2, 2,6,6- tetramethyl-l-piperidinyloxy (TEMPO) were used in combination to help initiate and control radical formation to prevent lateral overcuring. (See, e.g., Xiong, D.; Ruan, P.; Li, Z.; Yi, W.; Wang, J. A General Strategy for Sustainable 3D Printing Based on A Multifunctional Photoinitiator. Angewandte Chemie International Edition n / a (n / a), e202406047, the disclosure of which is incorporated herein by reference in its entirety). PAGES resins were formulated using BAPO and HMB but were adjusted to use BAPO and TEMPO if lateral overcuring was observed. Ethyl acetate was used to adjust the resin viscosity. The PAGES oligomers and thiol crosslinker serve as the basis for the network formation during the 3D printing process. The pendant terminal alkene in each P AGES repeat unit undergo a thiol-ene addition reaction in the presence of a thiol group and UV light. Iha, R. K.; Wooley, K. L.; Nyström, A. M.; Burke, D. J.; Kade, M. J.; Hawker, C. J. Applications of Orthogonal “Click” Chemistries in the Synthesis of Functional Soft Materials. Chem. Rev. 2009, 109 (11), 5620 -5686, the disclosure of which is incorporated herein by reference in its entirety). Using a trifunctional thiol allowed for the individual PAGES oligomers to crosslink and form a solid network (FIGS. 15, 16). Additionally, the thiol selected for this study contained multiple ester groups, making it susceptible to hydrolytic degradation. (See, Shin, Y.; Becker, M. L. Gradient versus End-Capped Degradable Polymer Sequence Variations Result in Stiff to Elastic Photochemically 3D-Printed Substrates. Biomacromolecules 2022, 23 (5), 2106-2115; Rydholm, A. E.; Anseth, K. S.; Bowman, C. N. Effects of Neighboring Sulfides and pH on Ester Hydrolysis in Thiol-Acrylate Photopolymers. Acta Biomater 2007, 3 (4), 449-455, the disclosures of which are incorporated herein by reference in its entirety). The mass of thiol crosslinker added to each resin was scaled based on the targeted crosslink ratio (molar ratio of alkenes to thiols) within each print. The thiol-ene radical mechanism is UV-promoted, affording temporospatial control of crosslinking based on the location and timing of UV light. (See, e.g., Hoyle, C. E.; Bowman, C.N. Thiol -Ene Click Chemistry. Angewandte Chemie International Edition 2010, 49 (9), 1540- 1573, the disclosure of which is incorporated herein by reference in its entirety).

[0228] The components, crosslink ratio, crosslinks per chain. 100 μm layer print times, viscosity and gel points for the resins printed are set forth in Table 3, below.

[0229] Each resin formulation was tested to confirm that network formation occurred through thiol-ene additions, as opposed to pendent alkene moieties undergoing uncontrolled free radical coupling forming carbon-carbon linkages (See, Table 4).Control experiments revealed the absence of network formation in response to UV light without the thiol crosslinker. Several resin formulations without the thiol crosslinker were exposed to UV light (70 W, λ = 390-420 nm) for 15 minutes. Crosslinking was not observed, as no change in viscosity was seen in frequency sweep profiles after UV irradiation (FIG. 17). Insight into the network structure of the cured resin is essential to understanding the properties of the 3D printed materials such as mechanical strength and degradation profile. FT-IR spectra further confirmednetwork formation via thiol-ene addition through the absence of S-H stretching 2600-2550 cm-1that would be present if unreacted thiol crosslinker remained. Residual pendent alkene bending stretches at 995-885 cm-1were observed, as expected due to the sub-stochiometric crosslink ratios that were targeted (FIGS. 18A-B).

[0230] A simple cure test was used to determine optimal print time for a 100 μm thick layer (λ = 385 nm, 5 mW / cm2). Adjusting the layer cure time for each resin allows one to tune the light penetration depth, also known as the cure depth, which is essential for high resolution printing.4,6Cure testing was completed by printing four single-layer disks (100 μm) at varying 100 μm layer print times and measuring the height of the disks post-print (Tables 5-10) to determine the cure depth.

[0231] It was experimentally determined that using an ETEC D4K Pro printer produced high resolution prints using a cure depth between 350-500 μm. If a lower cure depth was used, structures would generally be under-cured, display poor network formation and resolution, and would occasionally fail completely due to layer delamination. If a greater cure depth was used, structures would over-cure, resulting in poor resolution and areas surrounding printed structures to be unintentionally solidified due to over-exposure. While achieving a cure depth 3.5-5x that of the print height seems unideal, this proved to be necessary- to avoid layer delamination, even in prints with varying geometries throughout the vertical axis. Previous reports detailing multi-layer printing corroborate these findings, showing that each layer within a multi-layer part experiences additional curing from the printing of subsequent layers, which means that the cure depth is greater than the layer thickness. (See, e.g., Kuang, X.; Wu, J.; Chen, K.; Zhao, Z.; Ding, Z.; Hu, F.; Fang,D.; Qi, H. J. “Grayscale Digital Light Processing 3D Printing for Highly Functionally Graded Materials.” Science Advances 2019, 5 (5), eaav5790, the disclosure of which is incorporated herein by reference in its entirety). Each resin was cure tested until a 100 μm layer print time was determined that would produce a disk that is approximately 400 μm thick when the printer is set to print a single-layer, 100 μm thick disk.

[0232] The range of the 100 μm layer print time varied between 1.25 and 13 seconds for each print. This caused the overall print time for each 32-layer part to vary from 23 to 30 minutes. These rapid print times for a variety of resin compositions could allow PAGES polymer to be translated to commercial, industrial, or clinical applications where rapid part fabrication is advantageous. Additionally, printing solvent free PAGES using an unmodified, commercially available DLP 3D printer at ambient temperature further showcases its potential for safe, commercial translation.

[0233] Gel point calculations were determined for each resin using Equation 1 where Pcis the critical extent of reaction for gelation to occur, r is the reactant ratio, p is the multifunctionality ratio, and f is the functionality.Determining the critical extent of reaction for gelation to occur, Pc, aids in the prediction of a successful print. It was observed that all resins that printed successfully with no significant complications had a Pc< 1 (FIGS. 19A-C). Conversely, prints with Pc> 1 visibly had lower resolution, a decreased output of intact parts, and were significantly more challenging to handle before post-print curing in an UV oven. Therefore, a critical gel point equal to one represents a threshold for print quality (FIG. 20). While not wanting to be bound by theory, it is believed that when the critical gel point is above one, print quality and resolution are compromised due to the impossibility of a reaction, reaching more than 100% completion and thus a percolated network, cannot form. It is believed that when the critical gel point is below one, the reaction can achieve the conversion necessary' for its critical gel point which allows for a percolated network to form, leading to increased print quality and resolution. Normalization of crosslink ratio and DPncan be helpful to compare different resins. Normalization was completed by calculating the theoretical number of crosslinkers per chain using Equation 2.

[0234] A schematic of network formation during the 3D printing process can be visualized in FIG. 15. A comparison of a DP6PAGES printed at a 5:1 and 10:1 crosslink ratio were used to better understand the value of the theoretical number of crosslinks per chain. A 5:1 crosslink ratio with a DP6polymer allows for most of the polymer chains to be interconnected, whereas a 10:1 crosslink ratio does not provide enough crosslinks to form a continuous network. For a DP6oligomer printed at a 10: 1 crosslink ratio, there would only be 0.6 crosslinks per chain. This shows that there are fewer crosslinking points than there are oligomer chains, meaning a continuous network cannot form. Conversely, for a DP6oligomer printed at a 5:1 crosslink ratio, there would be 1.2 crosslinks per chain, therefore allowing all chains to become interconnected. Thus, resins that possess < 1.0 crosslinks per chain could lead to poor print resolution or even print failure while resins with > 1.0 crosslinks per chain establish a baseline threshold for print quality (FIG. 21). When the number of crosslinks per chain is below one, print quality and resolution are compromised due to there being too few crosslinks to connect all the chains. When the number of crosslinks per chain is greater than one, all chains are connected and a percolated network is formed, leading to increased print quality and resolution A positive correlation between crosslink density (q) calculated from DMA temperature sweeps and number of crosslinks per chain (FIG. 22) confirms that calculating the number of crosslinks per chain is a reliable normalization for the amount of crosslinking in different prints.

[0235] A schematic of network formation during the 3D printing process can be visualized in FIG. 15. Possible network defects that will detract from maximum theoretical mechanical properties include dangling thiols, dangling chain ends, and intramolecular reactions that form loops.Analysis of 3D Printed Parts.

[0236] Mechanical property analysis of materials was conducted by uniaxial tensile testing until failure using ASTM D638 Type V (63.5 x 9.5 x 3.2 mm) 3D printed tensile bars (FIGS. 23- 32, Table 11).Samples with a constant crosslink ratio but increasing DPnpossessed higher tensile modulus values (see, FIG. 33A-B). Networks of higher DPnoligomers have more crosslinks per chain at the same crosslink ratio. (See, e.g., Scheutz, G. M. et al. “Adaptable Crosslinks in Polymeric Materials: Resolving the Intersection of Thermoplastics and Thermosets.” J. Am. Chem. Soc. 2019, 141 (41), 16181-16196 and Danielsen, S. P. O. et al., “Molecular Characterization of Polymer Networks.” Chem. Rev. 2021, 121 (8), 5042-5092, the disclosures of which are incorporated herein by reference in its entirety). The number of crosslinks per chain for the DP6, DP9, and DP16networks crosslinked at a 5:1 ratio were 1.2, 1.8, and 3.2 crosslinks per chain, respectively (Table 3). Samples with a constant DPnbut increasing crosslink ratio exhibited smaller tensile modulus values due to decreasing crosslink density (FIG. 33A). Peterson, G. I. et al., “Production of Materials with Spatially-Controlled Cross-Link Density via Vat Photopolymerization.” ACS Appl. Mater. Interfaces 2016, 8 (42), 29037-29043. the disclosure of which is incorporated herein by reference in its entirety). Reduced crosslink density results on average in less crosslinks per chain, yielding softer and more flexible networks. This can be seen in comparing the number of crosslinks per chain for the DP165:1, 10:1, and 20:1 prints respectively: 3.2, 1.6, and 0.8 crosslinks per chain (Table 3).

[0237] An additional point of interest can be found in comparing print formulations that do not have a common crosslink ratio or DPn. The DP1620: 1 and DP910: 1 prints have similar tensile modulus values (FIG. 33 A) and stress-strain curves (FIG. 24A-B). They also have similar numbers of crosslinks per chain with DP1620:1 having approximately 0.8 crosslinks per chain and DP910:1 having 0.9 crosslinks per chain. This further illustrates that the number of crosslinks per chain can be used to normalize the effects of crosslink ratio and DPnso different prints can be accurately compared. When plotting the measured tensile modulus values against the number of crosslinks per chain for each print, a linear trend can be identified (FIG. 33B). As the number of crosslinks per chain increases, the tensile modulus of the 3D printed structure also increases. The slope of this line indicates that for every unit increase in number of crosslinks per chain, there is a corresponding tensile modulus increase of 2.4 MPa.

[0238] Further analysis of mechanical properties was conducted using dynamic mechanical analysis (DMA) performed on 3D printed bars (18 x 3.6 x 2.4 mm). Analysis of elongational storage modulus through frequency sweeps (FIGS. 34-42, Table 12) revealed similar trends as those seen for tensile modulus.

[0239] As DPnincreased, storage modulus increased, and as crosslink density decreased, storage modulus decreased. Additionally, DP1620:1 and DP910:1 exhibited similar behaviors. Analysis of elongational storage modulus and tan(δ) curves from temperature sweeps revealed both curves shifting towards higher temperatures as crosslink density increases, representing an increase in network stiffness. This shift can be observed as DPnincreases (FIG. 43A-B) and crosslink ratio decreases (FIG. 43C-D) when the other variable is held constant because both adjustments would cause an increase in crosslinking density to occur (Table 13). sweeps of b on (n = 1).Tg(°QAs can be seen, the Tgincreases with the chain length.

[0240] Ail formulations that included solvent experienced part shrinkage. This shrinkage is caused by multiple phenomena, including shortening of intramolecular distance between molecules during curing and, most significantly, evaporation of solvent. (See, e.g., Sandmeier, M. et al., “Solvent-Free Three-Dimensional Printing of Biodegradable Elastomers Using Liquid Macrophotoinitiators.” Macromolecules 2021, 54 (17), 7830-7839 and Zhang, Q. et al., “Design for the Reduction of Volume Shrinkage-Induced Distortion in Digital Light Processing 3D Printing.” Extreme Mechanics Letters 2021, 48, 101403, the disclosures of which are incorporated herein by reference in their entirety). Part thickness, which tends to be the most tightly controlled dimension in DLP printed parts because it is not impacted by lateral overcuring, ranged from 3% to 14% shrinkage with an average of 9.5% shrinkage between all prints with an 80% polymer resin composition. (See, e.g., FIGS 79-81) This nonuniform shrinkage not only imposes challenges for 3D printed part tolerancing, but also imposes residual stresses on 3D printed parts which can lead to early and unexpected part failure. (See, e.g., Luo, Y.; Le Fer, G.; Dean, D.; Becker, M. L. 3D Printing of Poly (Propylene Fumarate) “Oligomers: Evaluation of Resin Viscosity, Printing Characteristics and Mechanical Properties.” Biomacromolecules 2019, 20 (4), 1699-1708; Barker, C. M. et al., “Solvent-Free Vat Photopolymerization of Unsaturated Polyesters: Structure-Property Relationships for Depolymerization.” MRS Communications 2023, 13 (S) ', 841-847; Cheng, X. et al., “Simultaneously Enhanced Chain Flexibility, Three Dimensional Printability, and Reduction of Shrinkage Stress in Biodegradable and Photocurable Multiblock Copolymers.” Macromolecules 2023, acs.macromol.3c00298; and Li, S.; Cui, Y.; Li, J. “Thiol-Terminated Hyperbranched Polymer for DLP 3D Printing: Performance Evaluati on of a Low Shri nkage Photosensitive Resin ” Journal of Applied Polymer Science 2021, 138 (22), 50525, the disclosures of which are incorporated herein by reference in their entirety). As will be apparent, minimizing part shrinkage minimizes issues associated with tolerancing and residual stress.

[0241] The degradation profile of each print formulation was studied under accelerated degradation conditions (1 N NaOH) with agitation at 37 °C (FIG. 44A). PAGES primarily degrades through hydrolysis of ester bonds in the polymer backbone. (See, e.g., Fisher, J. P.; Holland, T. A.; Dean, D.; Mikos, A. G. Photoinitiated Cross-Linking of the Biodegradable Polyester Polypropylene Fumarate). Part II. In Vitro Degradation. Biomacromolecules 2003, 4 (5), 1335-1342; Woodard, L. N.; Grunlan, M. A. Hydrolytic Degradation and Erosion of Polyester Biomaterials. ACS Macro Lett. 2018, 7 (8), 976-982; and Govindarajan, S. R. et al. “A Solventand Initiator Free, Low-Modulus, Degradable Polyester Platform with Modular Functionality for Ambient-Temperature 3D Printing.” Macromolecules 2016, 49 (7), 2429-2437, the disclosures of which are incorporated herein by reference in their entirety). The selected crosslinker also contains ester bonds, further increasing degradability of the polymer network. Degradation rate within each 3D printed part is dependent on the reacti on rate for hydrolyzing the ester bonds in the crosslinked network, the diffusion rate of the solution into the network, and the diffusion rate of degradation products out of the network. (See, e.g., Braunecker, J.; Baba, M.; Milroy, G. E.; Cameron, R. E. “The Effects of Molecular Weight and Porosity on the Degradation and Drug Release from Polyglycolide.” International Journal of Pharmaceutics 2004, 282 (1), 19—34, the disclosure of which is incorporated herein by reference in its entirety). Samples of varying DPndisplayed differences in degradation rate (FIG. 44A). Samples with lower DPndegraded the fastest while samples with higher DPndegraded more slowly likely because longer chains would need to experience more degradation to form soluble oligomers that can diffuse out of the network. (See, e.g., Cai, M.; Liu, FL; Jiang, Y.; Wang, J.; Zhang, S. A High-Strength Biodegradable Thermoset Polymer for Internal Fixation Bone Screws: Preparation, in Vitro and in Vivo Evaluation. Colloids and Surfaces B: Biointerfaces 2019, 183, 110445, the disclosure of which is incorporated herein by reference in its entirety). While not wishing to be bound by theory, it is believed that the lack of notable difference in degradation rate between formulations with constant DPnbut varying crosslink ratio occurs because not all bonds must be broken in order for degradation to occur; only enough bonds must be broken to form oligomers that are small enough to solubilize and diffuse out of the network. Complete degradation occurred for all 3D printed samples. The fastest degrading formulation (DP65:1) experienced complete degradation in 12 days under accelerated conditions, whereas the slowest degrading formulation (DP1610:1) experienced complete degradation in 40 days under accelerated conditions. Fully degradable materials are desirable for many applications such as biomedical implants, tissue engineering, waste reduction, and green engineering efforts. (See, e.g., Woodard, L. N.; Grunlan, M. A. “Hydrolytic Degradation and Erosion of Polyester Biomaterials” A CS Macro Lett. 2018, 7 (8), 976-982; Guo, Y.; Chen, S.; Sun, L.; Yang, L.; Zhang, L.; Lou, J.; You, Z. Degradable and Fully Recyclable Dynamic Thermoset Elastomer for 3D-Printed Wearable Electronics. Advanced Functional Materials 2021, 31 (9), 2009799 and Mason Wu, Y.-C.; Chyr, G.; Park, H.; Makar-Limanov, A.; Shi, Y.; M. DeSimone, J.; Bao, Z. “Stretchable, Recyclable Thermosets via Photopolymerization and 3D Printing ofHemiacetal Ester-Based Resins.” Chemical Science 2023, 14 (44), 12535-12540, the disclosures of which are incorporated herein by reference in their entirety). The ability to adjust the degradation speed of the prints is especially important for biomedical implants and tissue engineering so that degradation profiles can match the time frame of the intended application. (See, e.g., P. Brannigan, R.; P. Dove, A. Synthesis, Properties and Biomedical Applications of Hydrolytically Degradable Materials Based on Aliphatic Polyesters and Polycarbonates. Biomaterials Science 2017, 5 (1), 9-21, the disclosures of which are incorporated herein by reference in their entirety).

[0242] Crosslink density of each solvent-containing formulation was further investigated by completing a swelling study of each formulation in ethyl acetate for 48 hours (FIG. 44B). Trends in swelling data corroborate mechanical property trends described previously. First, when comparing prints with a constant crosslink ratio but varying DPn, as degree of polymerization increases, swelling decreases. This suggests that increasing the DPnwhile maintaining the crosslink ratio will lead to a more crosslinked network, which will swell less. (See, e.g., Shin, Y.; Becker, M. L. “Gradient versus End-Capped Degradable Polymer Sequence Variations Result in Stiff to Elastic Photochemically 3D-Printed Substrates.” Biomacromolecules 2022, 23 (5), 2106- 2115 and Kirillova, A.; Yeazel, T. R.; Gall, K; Becker, M. L. Thiol-Based Three-Dimensional Printing of Fully Degradable Polypropylene Fumarate) Star Polymers. ACS Appl. Mater. Interfaces 2022, acsami.2c06553, the disclosures of which are incorporated herein by reference in their entirety). When comparing groups with a constant DPnbut varying crosslink ratio, as crosslink ratio increases and resulting network density decreases, swelling increases. Again, this follows the inverse relationship between swelling and crosslink density. (See, e.g., Shin, Y.; Becker, M. L. “Gradient versus End-Capped Degradable Polymer Sequence Variations Result in Stiff to Elastic Photochemically 3D-Printed Substrates.” Biomacromolecules 2022, 23 (5), 2106- 2115 and Kirillova, A.; Yeazel, T. R.; Gall, K.; Becker, M. L. Thiol-Based Three-Dimensional Printing of Fully Degradable Polypropylene Fumarate) Star Polymers. ACS Appl. Mater. Interfaces 2022, acsami.2c06553, the disclosures of which are incorporated herein by reference in their entirety). These trends help to explain why the DP165:1 formulation swelled the least out of all the prints: it has both the lowest crosslink ratio and the highest DPnstudied, thus causing it to be the most densely crosslinked and consequently least swellable. The swelling results also trend with the number of crosslinks per chain. Because the DP165: 1 formulation has the highest numberof crosslinks per chain with 3.2 crosslinks per chain, it is the most crosslinked and least swellable. When plotting the number of crosslinks per chain versus the swelling percentage of each formulation (FIG. 45), the inverse relationship between amount of crosslinking and swelling can be seen. Similar trends were identified between swelling and crosslink density (q) calculated using DMA temperature sweeps (FIG. 46).

[0243] The sol fraction for each formulation was also calculated from the ethyl acetate swelling study (FIG. 44C). Sol fraction is the proportion of the printed part that is made up of unlinked polymer chains that does not contribute to the elastic properties of the solid. (See, e.g., Azoug, A.; Constantinescu, A.; Pradeilles-Duval, R. M.; Vallat, M. F.; Neviere, R.; Haidar, B. “Effect of the Sol Fraction and Hydrostatic Deformation on the Viscoelastic Behavior of Prestrained Highly Filled Elastomers.” Journal of Applied Polymer Science 2013, 127 (3), 1772— 1780, the disclosure of which is incorporated herein by reference in its entirety).The sol fraction can be determined by extracting the unlinked polymer chains from the polymer network into a good solvent. When comparing prints with a constant crosslink ratio but vaiying DPn, sol fraction decreases as DPnincreases. (See, e.g., Azoug, A.; Constantinescu, A.; Pradeilles-Duval, R. M.; Vallat, M. F.; Neviere, R.; Haidar, B. “Effect of the Sol Fraction and Hydrostatic Deformation on the Viscoelastic Behavior of Prestrained Highly Filled Elastomers.” Journal of Applied Polymer Science 2013, 127 (3), 1772-1780, the disclosure of which is incorporated herein by reference in its entirety). At the same crosslink ratio, shorter chains are more likely to be unlinked, as they have less crosslinks per chain. When comparing prints with a constant DPnbut varying crosslink ratio, sol fraction increases as crosslink ratio increases. Sol fraction can be related to the normalized value of the number of crosslinks per chain for each formulation. As the number of crosslinks per chain increases, the sol fraction decreases because there are fewer unlinked chains throughout the sample. When plotting the number of crosslinks per chain versus the sol fraction of each formulation (FIG. 47), the inverse relationship between crosslink density and sol fraction can be seen. These trends were further confirmed by identifying similar relationships between sol fraction and crosslink density (q) calculated using DMA temperature sweeps (FIG. 48).Solvent Free Printing.

[0244] Following the assessment of physi cal and mechani cal properties of structures printed from different DPnand crosslink ratios, the influence of solvent on the resin was investigated. Resins DP6 5:1 and DP9 5:1 were selected because they had neat viscosity values near or belowthe printable limit (10 Pa.s or 10,000cP) for DLP printing. Four DP6formulations and two DP9formulations all crosslinked at 5: 1 ratio with varying fractions of polymer and solvent were compared directly in this study. Each resin formulation was cure tested, printed, and post cured using conditions described above (Tables 14-17),Shrinkage of the parts is shown to decrease as the solvent fraction of the resin is reduced (FIG. 49 A, see also FIGS. 79-81). Parts resulting from DP6formulations exhibit 14% shrinkage at 80% polymer concentrations to less than 0.4% shrinkage in the solvent free (99+% polymer concentration) resin formulation. In general, solvent free parts experienced the least shrinkage with the DP65:1 parts experiencing 0.4% shrinkage and the DP95:1 parts experiencing 0.3% shrinkage.

[0245] Mechanical properties were analyzed using uniaxial tensile testing until failure, DMA temperature sweeps, and DMA frequency sweeps. Comparison of storage modulus (FIG. 49B, FIGS. 50-52, Table 19), stress-strain curves (FIGS. 49C-D, 53-57, Table 18), tensile modulus (FIG. 49E), and temperature sweep curves (FIGS. 58A-B, Table 20) reveal that there were minimal significant differences in mechanical properties between each DP6formulation with a 5:1 crosslink ratio.This is believed to be due to the limited connectivity in the network.

[0246] However, there were significant differences between each DP9formulation with a 5:1 crosslink ratio: solvent free printing unexpectedly produced parts that were stronger than those printed with solvent (FIGS. 59-63A-B, Tables 21-23).While not wishing to be bound by theory, it is believed that this difference is likely due to the formation of more intermolecular crosslinks instead of intramolecular crosslinks when the reaction concentration is higher in the solvent free formulation. It is likely that the solvent free DP6formulations also contain more intermolecular crosslinking, but the impacts are less pronounced due to the shorter chain length.

[0247] Swelling and sol fraction were determined for all low' solvent and solvent free prints in an ethyl acetate swelling study. Statistically significant swelling differences between solvent containing and solvent free prints confirm a difference in crosslink density between networks formed in the presence and absence of solvent. Decreased swelling observed for both DP699+% and DP999+% formulations further confinn an unexpected increased formation of intermolecular crosslinks in solvent free formulations. The lack of significant differences between sol fraction measurements for both DP6and DP9 oligomers indicates that the number of chains connected in each network is similar, as expected because the number of crosslinks per chain is not dependent on the presence or absence of solvent. However, the sol fraction does not show how the chains are connected (intermolecular versus intramolecular crosslinking) and thus cannot be used to confirm network structure differences between solvent containing and solvent free prints.

[0248] Solvent free PAGES resin capabilities were further demonstrated by printing structures with varying geometry throughout the z-axis. Solvent free 3D Benchy shape (FIG. 64A- C) (.stl files publicly available at https : / / www.3 dbenchy.com / ) and solvent free gyroid structures (FIG. 64D-F) demonstrate precise control over curing in all dimensions. Micro-computed tomography (pCT) images of 3D Benchy (FIG. 64B-C) displayed resolved vertical and horizontal structures, holes, overhangs, and organic shapes, while pCT images of gyroid structures (FIG. 64D-E) displayed continuous porosity throughout a triply periodic minimal surface design. Scanning electron microscopy (SEM) imaging (FIG. 65) provides further insight into printer resolution. The layered nature of DLP printing is demonstrated by the individual 100 μm layers visible within the pore. The use of a pixelated light engine is evident by the 50 μm x 50 μm grid pattern displayed on the surface layer of the gyroid.Solvent Free High Resolution Printing

[0249] Cure testing was performed on a solvent free DP65:1 resin formulation that included 0.04 wt.% Sudan I dye. A 100 μm layer print time of 40 s was used for these prints.

[0250] Cure testing is used to determine the layer print time (Table 24). Average disk height is a measurement of cure depth. A cure depth of -500 um, which corresponds to a layer cure time of 40 s, was selected for this print to ensure that each 100 um layer was cured and subsequently adhered to previously printed layers to avoid layer delamination. After printing each layer, the printer was set to first move the build tray upward to the next layer position at 20 um / s and then wait 10 seconds before printing the next layer. This allowed fresh resin to refill the void space left behind as the build tray moved up. The designs consisted of 240 layers, each 100 um thick. After printing, printed parts were cleaned using pressurized air and post cured under UV light for 15 minutes. Printed parts were imaged using uCT and SEM to verify their resolution throughout the entire part. Photographs of solvent free high resolution samples are shown in FIGS. 64A-F, 65, and 66A-D.Conclusions

[0251] Furthering the fields of additive manufacturing and their use in regenerative medicine will rely on the development of new degradable materials. Poly(allyl glycidyl ether succinate) has been demonstrated to be a highly scalable, widely tunable, and degradable polymer for use in DLP 3D printing. Solvent free, ambient, high resolution 3D printing can be achieved using PAGES due to its inherent low viscosity, affording minimal shrinkage and residual stress in 3D printed parts. 3D printed PAGES is a soft material due to its low modulus values. Degradable materials in this mechanical regime that can be 3D printed into complex shapes are exceedingly rare, thus, it has potential applications in soft tissue regeneration. For example, the average tensile modulus and ultimate tensile strength of the temporal muscle, which is frequently used as a graft in craniofacial surgery, is 1.58 ± 0.64 MPa and 260 ± 110 kPa respectively, which is very close to the PAGES properties reported here. (See, Singh, G.; Chanda, A. Mechanical Properties of Whole-Body Soft Human Tissues: A Review. Biomed. Mater. 2021, 16 (6), 062004, the disclosure of which is incorporated herein by reference in its entirety. Other tissues with similar tensile moduli to PAGES prints from this work include gallbladder, uterine, bladder, colon, nasal cavity, and small intestine.Outside of biomaterials, soft materials have gained attention in a wide range of applications including nanotechnology, wearable electronics, microfluidics, robotics, and more.EXAMPLES

[0252] The following examples are offered to more fully illustrate the invention, but are not to be construed as limiting the scope thereof. Further, while some of examples may include conclusions about the way the invention may function, the inventors do not intend to be bound by those conclusions, but put them forth only as possible explanations. Moreover, unless noted by use of past tense, presentation of an example does not imply that an experiment or procedure was, or was not, conducted, or that results were, or were not actually obtained. Efforts have been made to ensure accuracy with respect to numbers used (e.g., amounts, temperature), but some experimental errors and deviations may be present. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric.Examples 1-10

[0253] To more fully illustrate and reduce the invention to practice, five batches of the PAGES copolymers and resins of the present invention (designated MIS-I-140, MIS-I-166, MIS- I-171, MIS-I-182 and MIS-II-4) were synthesized as set forth above, and evaluated by Nuclear Magnetic Resonance (NMR) Spectroscopy, Size-Exclusion Chromatography (SEC), Matrix- Assisted Laser Desorption / Ionization Time of Flight Mass Spectrometry (MALDI TOF), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Rheometry, and Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) Spectroscopy. Further, 3D structures printed from these resins were evaluated by mechanical (tensile) testing.Materials

[0254] All solvents were purchased from Sigma Aldrich and were dried using a Pure Solv MD 5 INERT solvent purification system. Allyl glycidyl ether was purchased from Thermo Scientific and was sparged immediately before use. 1,6-hexanediol and trimethylolpropane tris (3- mercaptopropi onate) were purchased from Sigma Aldrich and were used as received. Succinic anhydride was purchased from Thermo Scientific and was used as received. The catalyst Mg(BHT)2(THF)2 was synthesized using previously reported methods.Example 1Synthesis of Poly (Allyl Glycidyl Ether Succinate) Copolymers.

[0255] Poly(Allyl Glycidyl Ether Succinate) (PAGES) was synthesized using the ring-open copolymerization (ROCOP) of succinic anhydride (SAn) and allyl glycidyl ether (AGE) with 1,6- hexane diol as the bifunctional initiator in toluene using Mg(BHT)2(THF)2 as a catalyst. (See, Scheme 4, below). The monomer conversions were monitored in crude samples from the reaction mixture using1H-NMR in CDCl3. After polymerization, the PAGES was purified using precipitation, liquid-liquid extraction, and silica plug methods.where x. is an integer from about 5 to about 50.

[0256] The PAGES copolymers (MIS-I-140, MIS-I-166, MIS-I-171,) and resins of the present invention were synthesized as described above. PAGES copolymers MIS-I-140, MIS-I- 182, and MIS-II-4 were synthesized using a slight excess of AGE. The theoretical yield, catalyst loading, and reaction time of each of these batches of PAGES polymers are set forth in Table 25, below.Example 2Nuclear Magnetic Resonance (NMR) Spectroscopy.

[0257] 1H-NMR,13C-NMR, and1H-1H-COSY NMR were recorded using a 700 MHz Bruker Avance III. Chemical shifts were recorded in parts per million (ppm) relative to the IMS reference resonance at 8=0.00. The1H-NMR of purified MIS-I-140 in CDCl3is shown in FIG. 67; the13C- NMR of purified MIS-I-140 in CDCI3 is shown in FIG. 68; and the1H-1H-COSY NMR of purified MIS-I-140 in CDCl3is shown in FIG. 69.1H-1H-COSY NMR (FIG. 69) was used to assign1H- NMR resonances to corresponding protons within the polymer (FIG. 67).

[0258] Reaction progress was monitored using1H-NMR in CDCl3. Time to reaction completion was decreased by adjusting reaction target degree of polymerization to be higher than ideal degree of polymerization to reduce time spent reacting in the final portion of the reaction in which monomer concentrations are low. Additionally, by increasing reaction size, the amount of monomer was increased, thus increasing the statistical likeliness of a collision allowing for reaction between two monomers, thus inherently decreasing reaction time, as can be seen when comparing the reaction time of MIS-I-140 to the rest of the samples. The degree of polymerization for MIS-I-140, MIS-I-166, MIS-I-171, MIS-I-182, and MIS-II-4are reported in Table 26, below. 26 calculated from1H-NMR integrations.

[0259] The degree of polymerization for each sample was calculated from1H-NMR integrations. The resonance occurring at 1.61 ppm was set to have an integration value of 4.00 because it corresponded to four protons on the initiator. The degree of polymerization was calculated as half of the integration value of the resonances occurring at 4.31 and 4.20 ppm.Example 3 Size-Exclusion Chromatography (SEC).

[0260] Number average molecular mass (Mn), weight average molecular mass (Mw), and dispersity (D) was determined using a Tosoh Bioscience HLC-8420 GPC with an RI detector. Molecular masses were determined using a calibration curve derived from polystyrene standards in tetrahydrofuran (THF) with eluent flowing at 0.5 mL / min and a sample concentration of approximately 2 mg / mL. Normalized RI SEC curves of each batch of PAGES polymer in THF are shown in FIG. 70. The number average molecular mass (Mn), weight average molecular mass (Mw), and dispersity (D) for MIS-I-140, MIS-I-166, MIS-I-171, MIS-I-182, and MIS-H-4 are reported in Table 71, below.Number average molecular weight, weight average molecular weight, and dispersity of each batch of PAGES calculated from Rf SEC curves.

[0261] PAGES polymers display bimodal SEC curves in THE, showing that two different populations of chains of significantly different lengths exist. This could be due to two possibilities: the reaction was stopped before achieving full conversion or there are two different initiating species present. For the first possibility, if the reaction was stopped prematurely, there is a chance that one portion of the reaction mixture has reached higher conversion than another portion. For the second possibility, if the AGE underwent a ring-opening reaction, it could act as a diol initiator with one primary alcohol initiation site and one secondary alcohol initiation site. The secondary initiation site would react more slowly than the primary initiation site due to steric effects. If this ring-opened AGE were to initiate polymerizations as well as the intended diol initiator has two primary alcohol initiation sites, it would cause there to be two separate polymer populations. One population would have the intended diol initiator, causing it to have an overall higher molecular weight due to the two faster, primary initiation sites, and the other population would have the ring-opened AGE as the initiator, causing it to have an overall lower molecular weight due to the one slower, secondary initiation site.

[0262] The number average molecular weight and weight average molecular weight of each sample are not absolute values due to the reliance of the data on a standardized curve based on polystyrene samples. Due to significant differences in chemical structure and behavior of the PAGES polymer in comparison to polystyrene, the average molecular weight values produced can only be used for relative comparison of molecular weights against one another and should not be used to calculate degree of polymerization. The theoretical molecular weight of a PAGES polymer initiated with 1,6-hexanediol with a degree of polymerization of 20 is 4419.9 g / mol.Example 4Matrix-Assisted. Laser Desorption / Ionization Time of Flight Mass Spectrometry (MALDI TOF).

[0263] MALDI TOF was performed using a Bruker Autoflex Speed LRF MALDI-TOF system. The samples were diluted in acetone, combined with trans-2-[3-(4-tert-butylphenyl)-2- methyl-2-propenylidene]malononitrile (DCTB) matrix, and spotted by dried droplet on a polished steel plate. All samples were analyzed in linear positive ion mode against adrenocorticotropic hormone (ACTH(18-39)) and insulin standards. MALDI-TOF end group analysis was used to determine initiating species. The MALDI-TOF curve of MIS-I-140 is shown in FIG. 72 and the MALDI-TOF curve of MIS-I-166 is shown in FIG. 73.Example 5 Differential Scanning Calorimetry (DSC).

[0264] Thermal analysis was performed on pure PAGES as well as crosslinked PAGES samples on a TA Instruments Discovery DSC 250. The temperature range scanned was -60 °C to 70 °C at a 10 °C / min ramp rate. Glass transition temperature (Tg) was determined as the midpoint of the transition in the second heating cycle. The results are shown in Table 28 and FIG. 74. The DSC curve of MIS-I-140 showing the Tgoccurring at the midpoint of the transition in the second heating cycle is shown in FIG. 74. As can be seen, the Tgof the MIS-I-140 PAGES samples occurs near -45 °C (FIG. 74).Example 6 Thermogravimetric Analysis (TGA).

[0265] Thermal analysis was performed on pure PAGES as well as crosslinked PAGES samples on a TA Instruments Discovery TGA 550, The TGA cycle run was either a temperature ramp from 30 °C to 600 °C at a 20 °C / min ramp rate or the temperature was ramped to 100 °C at 10 °C / min, held isothermally for 30 minutes, equilibrated at 30 °C, and finally ramped from 30 °C to 400 °C at 10 °C / min. Degradation temperature (Td) was determined as the temperature at both 5% and 10% mass loss. The results are shown in FIG. 75.

[0266] The TGA curves of the PAGES samples are shown in FIG. 75 and the degradation temperature of PAGES co polymer samples at both 5% and 10% mass loss are reported in Table 29, below.

[0267] As can be seen, the MIS-I-140 and MIS-I-166 samples have lower Td values than do the MIS-I-171 and MIS-I-182 samples due to differences in purification methods. Samples MIS- I-171 and MIS-I-182 both underwent purification via a silica plug column, which helped to remove Mg(BHT)2(THF)2 catalyst from the polymer. It is believed that the decreasing amount of catalyst caused the degradation temperature to increase.Example 7 Rheology.

[0268] Complex viscosity was measured using a TA Instruments Discovery HR-3 Hybrid Rheometer. Samples were placed on 20 mm parallel plate geometry with a 0.2 mm gap. The complex viscosity was collected over a frequency sweep from 0.1 rad / s to 500 rad / s at 10% strainand 25 °C. Zero shear viscosity of samples was determined by extrapolating complex viscosity curves to 0 rad / s. The results are show in FIG. 76.

[0269] As set forth above, PAGES polymers according to the present invention have a low viscosity, even when not diluted with any solvent. The maximum viscosity for a resin that can be successfully printed in a Carbon M2 printer is 10 Pa.s, whereas the viscosity of most neat PAGES polymers is 5.5 Pa.s. (See, FIG. 71). Because of this, most PAGES polymers can be 3D printed solvent free.

[0270] It has been found, moreover, that with changes to the synthesis process, PAGES complex viscosity can be tuned. In the synthesis of MIS-I-171,for example, a 1:1 ratio of allyl glycidyl ether and succinic anhydride was used, thus causing the end group of the chain to be statistically determined. This causes changes to viscosity because any end groups resulting from the succinic anhydride monomer would be capable of hydrogen bonding, thus increasing the viscosity of the polymer. The higher viscosity value of MIS-I-182 is not attributed to end group effects but instead to higher average molecular weight values, as can be seen in Table 26 (see, FIG. 70, Table 26).Example 8Attenuated Total Reflection Fourier Transform Infrared (ATR FTIR) Spectroscopy.

[0271] Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectra of pure PAGES copolymer was collected using a Thermo Scientific Nicolet i S50 FT-IR spectrometer with a built-in iS50 diamond ATR. The results The FTIR curve of MIS-I-140 is attached as FIG. 77.Example 9 3D Printing.

[0272] 3D printing resins were prepared by adding an operative amount of photoinitiator (phenylbis-(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO)); a radical scavenger (oxybenzone (2-hydroxy-4-methoxybenzophenone (HMB))); and a thiol crosslinker (trimethylolpropane tris(3 - mercaptopropionate)) to the purified PAGES polymer made in Example . 0.6 wt.% BAPO and 0.4 wt.% HMB were used rel ative to the mass of the polymer. The amount of thiol crosslinker added was determined by the desired crosslinking ratio (in this case 5:1), defined as the ratio of alkene bonds in the polymer to the thiol groups available for chemical crosslinking (alkene:thiol). The viscosity was too high in resins comprising polymers MIS-I-166 and MIS-I-171, whose end group control was not refined due to hydrogen bonding effects and polymers with larger DP6like MIS-1-182 (see, Example 7, above). If needed, ethyl acetate can be added to the resins for printing to dilute the viscosity or alter the density of the resin. Tensile bars (ASTM D368 Type V) were printed using an EnvisionTec D4K Pro DLP 3D printer. Printed samples were washed using ethyl acetate and isopropyl alcohol, submerged in deionized (DI) water, and cured in a B9Creations B9 Model Cure XL UV oven for 15 minutes. Samples were then dried in a Thermo Scientific Lindberg / Blue M Vacuum Oven at 60 °C for 6 days.Example 10 Tensile Testing.

[0273] Uniaxial tensile testing was performed on 3D printed samples of each resin using an AMETEK LLOYD INSTRUMENTS LRX Plus Materials Testing Machine. Force, displacement, stress, and strain were measured using a 50 N load cell at a 10 mm / min extension rate. The ultimate tensile strength was determined as the maximum recorded stress value. The strain at break was determined as the maximum recorded strain value. The modulus was determined as the slope of the stress-strain curve between 0% and 3% strain.

[0274] Stress strain curves generated during uniaxial tensile testing of MIS-I-166 at a 5:1 crosslink ratio are shown in FIG. 78. The measured ultimate tensile strength, strain at break, and modulus are set forth in Table 30, below.Examples 11 to 22

[0275] To more fully illustrate and reduce the invention to practice, the PAGES copolymers having different degrees of polymerization (DP) and resins having differing crosslink ratios were synthesized as set forth above and evaluated by Nuclear Magnetic Resonance (NMR) Spectroscopy, Size-Exclusion Chromatography (SEC), Matrix-Assisted Laser Desorption / Ionization Time of Flight Mass Spectrometry (MALDI TOF), Differential ScanningCalorimetry (DSC), Thermogravimetric Analysis (TGA), Rheometry, and Attenuated Total Reflection Fourier Transform Infrared (ATR FTIR) Spectroscopy. Further, 3D structures printed from these resins were evaluated by mechanical (tensile) testing.Materials

[0276] Tetrahydrofuran and toluene were purchased from Sigma Aldrich and were dri ed using a Pure Solv MD 5 INERT solvent purification system. Chloroform and hexanes were purchased from Sigma Aldrich and were used as received. n-Butyl-seobutyl magnesium 0.7 M solution in hexanes, 2,6-di-tert-butyl-4-methylphenol (BHT), allyl glycidyl ether, 1,6-hexanediol, trimethylolpropane tris (3-mercaptopropionate), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), 2-hydroxy-4methoxybenzophenone (oxybenzone, HMB), and 2,2,6,6-tetramethyl- 1-piperidinyloxy (TEMPO) were purchased from Sigma Aldrich and were used as received. Succinic anhydride was purchased from Thenno Scientific and was used as received.Methods

[0277] Nuclear Magnetic Resonance (NMR) Spectroscopy.1H NMR (600 MHz),13C NMR (150 MHz),1H^H COSY NMR, and HSQC NMR were recorded using a Broker Avance III spectrometer. Chemical shifts were recorded in parts per million (ppm) relative to the TMS reference resonance at 5=0.00. Proton NMR was used to monitor reaction conversion and determine the degree of polymerization while13C NMR,1H COSY NMR and HSQC NMR were used to verify polymer sequence and structure.1H COSY NMR was conducted at 300 K, 8 FT scans, T2 = 2 second delay, spectra center of 6 ppm and width of 13 ppm.1H13C HSQC NMR. was conducted at 300 K using a gradient pulse, 8 scans, T2 = 1 second delay, 16 ppm1H NMR spectra width and 200 ppm13C spectra width.

[0278] Size-Exclusion Chromatography (SEC). Number average molecular mass (Mn), weight average molecular mass (Mw), and molar mass distribution (£)) were determined using a TOSOH Bioscience HLC-8320 GPC with a TSKgel GMHHR-N mixed bed column and an RI detector. Samples were prepared bis dissolving 3-5 mg of polymer in 2 mL HPLC -grade THF and then filtered through 0.2 μm PTFE filter. Molecular masses were determined using a calibration curve derived from NIST certified polystyrene standards in tetrahydrofuran (THF) with eluent flowing at 0.35 mL / rnin and a sample concentration of 2 mg / mL.

[0279] Matrix-Assisted Laser Desorption / Ionization Time of Flight Mass Spectrometry (MALDI TOF) MALDI TOF was performed using a Bruker Autoflex Speed LRF MALDI-TOF system. The samples combined in a 1:1000 volumetric ratio with trans-2-[3-(4-tert-butylphenyl)- 2-methyl-2-propenylidene]malononitrile (DCTB) matrix, and spotted on a polished steel plate. All samples were analyzed in both linear positive and reflectron positive ion mode. Spectra were collected using an average of three laser shots at 60% laser power. Number average molecular mass (Mn), weight average molecular mass (Mw), and molar mass distribution (£)) were calculated using the following equations where N is the intensity and M is the m / z value from the spectra:

[0280] Differential Scanning Calorimetry (DSC). Thermal analysi s was performed on a TA Instruments Discovery DSC 250. Each sample was prepared by loading 10 mg of material into an aluminum DSC crucible. The temperature range scanned was -60 °C to 70 °C at a 10 °C / min ramp rate under N2 gas flow. Two cycles were completed: the first to reset the material’s thermal history and the second to collect representative data. All measurements are reported against a sealed, empty reference crucible. Glass transition temperature (Tg) was determined as the midpoint of the transition in the second heating cycle.

[0281] Thermogravimetric Analysis (TGA). Thermal analysis was performed on a TA Instruments Discovery TGA 550. Each sample was prepared by loading 10 mg of material onto a platinum TGA pan. The temperature was ramped to 100 °C at 10 °C / min, held isothermally for 30 minutes, equilibrated at 30 °C, and finally ramped from 30 °C to 600 °C at 10 °C / min all under N2 gas flow. Degradation temperature (Td) was determined as the temperature at 10% mass loss.

[0282] Rheology. Complex viscosity was measured on n = 1 sample per mixture using a TA Instruments Discovery HR-3 Hybrid Rheometer. Each sample was prepared by mixing polymer with ethyl acetate according to the specified weight% of each for the given experiment using a spatula until a homogenous mixture was achieved. Samples were loaded on 20 mm parallel plategeometry with a 0.2 mm gap. A trim gap of 50 μm was used to ensure proper distribution of each sample between plates. The complex viscosity was collected over a frequency sweep from 0.1 rad / s to 500 rad / s at 10% strain and 25 °C. Viscosity of samples was determined as the complex viscosity at 10 rad / s.

[0283] Attenuated Total Reflection Fourier Transform Infrared (ATR FTIR) Spectroscopy. ATR-FTIR spectra were collected using a Thermo Scientific Nicolet iS50 FT-IR spectrometer with a built-in iS50 diamond ATR. Liquid samples were placed directly onto the ATR crystal using a pipette. Solid samples were placed on the ATR crystal and then secured using a lever to ensure proper contact between the solid samples and the crystal. The number of scans was set to 64 for both background and sample spectra collection.

[0284] Statistical Analysis. Statistical analysis was performed using Prism GraphPad software. Sample averages were compared using an ordinary one-way ANOVA test with statistical significance being determined as a calculated p-value < 0.05. Threshold values for levels of statistical significance are as follows: *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. Sample averages were compared to each other using a Tukey’s multiple comparisons test with statistical significance being determined as a calculated p-value < 0.05. Threshold values for levels of statistical significance are as follows: *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.Example 12Synthesis of Mg(BHT)2(THF)2 Catalyst for One-Pot Polymerization.

[0285] Mg(BHT)2(THF)2 was synthesized by reacting n-butyl-sec-butyl magnesium 0.7 M solution in hexanes with 2,6-di-tert-butyl-4-methylphenol (BHT) and tetrahydrofuran (THF) at room temperature under nitrogen atmosphere conditions as described previously.1Prior to synthesis, all glassware was oven dried at 150 °C and put under nitrogen atmosphere conditions using standard Schlenk line techniques. After reacting for 24 hours, excess THF was removed using a vacuum and the catalyst was dried for an additional 24 hours under vacuum. Due to the one-pot synthetic approach for the catalyst and polymer, the catalyst is not isolated, so a 100% yield is assumed in future calculations.Example 13General Procedure for the One-Pot Synthesis ofPoly(Allyl Glycidyl Ether Succinate).

[0286] Poly( Allyl Glycidyl Ether Succinate) (PAGES) was synthesized using a ring-opening copolymerization (ROCOP) of succinic anhydride and allyl glycidyl ether (with 1,6-hexane diol as the difunctional initiator in toluene with a Mg(BHT)2(THF)2 catalyst. Polymer synthesis occurred in the same glassware used to synthesize the Mg(BHT)2(THF)2 catalyst; thus, this is a one-pot catalyst and polymer reaction.

[0287] Polymers with different degrees of polymerization (DPn) were produced by adjusting the proportion of initiator to monomers (Table 31). The amount of toluene added to the reaction was determined to make the total reaction concentration 15 M. Catalyst loading was determined using a 0.01 molar ratio of catalyst to succinic anhydride. Prior to synthesis, all glassware was oven dried at 150 °C and put under inert atmosphere conditions using standard Schlenk line techniques with nitrogen gas. The reaction was maintained at 80 °C while being constantly stirred in an inert atmosphere using nitrogen gas for the entire reaction. The monomer conversion was monitored in crude samples from the reaction mixture using1H-NMR in CDCl3. After polymerization, PAGES was purified using precipitation into hexanes and filtration.

[0288] Poly(Allyl Glycidyl Ether Succinate) (PAGES) DP6: Previously synthesized and dried Mg(BHT)2(THF)2 (15.00 g, 0.024 mol, 0.06 eq) was dissolved in dry toluene (431 mL) in a 2L round bottom flask at 40 °C. While stirring, 1,6-hexanediol (48.42 g, 0.410 mol, 1 eq), allyl glycidyl ether (375.00 mL, 3.160 mol, 7.7 eq), and succinic anhydride (287.45 g, 2.872 mol, 7 eq) were added to the reactor. The temperature was increased to 80 °C. The monomer conversion was first monitored when the reaction was no longer cloudy, indicating that the succinic anhydride had fully solubilized. Post-purification1HNMR spectra revealed the following resonance shifts (ppm): 1H-NMR (600 MHz, CDCl3) δ 7.27, 5.87, 5.27, 5.20, 4.34, 4.22, 3.99, 3.56, 3.50, 3.46, 2.65, 1.63,1.38. Post-purification TGA revealed a Td of 312 °C. Post-purification DSC revealed a Tgof - 42°C. Post-purification MALDI TOF revealed a Mnof 1500 g / mol.

[0289] Poly(Allyl Glycidyl Ether Succinate) (PAGES) DP9: Previously synthesized and dried Mg(BHT)2(THF)2 (15.00 g, 0,024 mol, 0.1 eq) was dissolved in dry toluene (397 mL) in a 2L round bottom flask at 40 °C. While stirring, 1,6-hexanediol (29.10 g, 0.246 mol, 1 eq), allyl glycidyl ether (353.00 mL, 2.979 mol, 12.1 eq), and succinic anhydride (271.02 g, 2.708 mol, 11 eq) were added to the reactor. The temperature was increased to 80 °C. The monomer conversion was first monitored when the reaction was no longer cloudy, indicating that the succinic anhydride had fully solubilized. Post-purification1H NMR spectra revealed the following resonance shifts (ppm):1H NMR. (600 MHz, CDCl3) 8 7.28, 5.87, 5.28, 5.19, 4.34, 4.22, 3.99, 3.56, 3.50, 3.47, 2.64, 1.64, 1.38. Post-purification TGA revealed a Ta of 313°C. Post-purification DSC revealed a Tgof -39°C. Post-purification MALDI TOF revealed a Mnof 2100 g / mol.

[0290] Poly(Allyl Glycidyl Ether Succinate) (PAGES) DP16: Previously synthesized and dried Mg(BHT)2(THF)2 (21.00 g, 0.034 mol, 0.2 eq) was dissolved in dry toluene (522 mL) in a 2L round bottom flask at 40 °C. While stirring, 1,6-hexanediol (20.37 g, 0.172 mol, 1 eq), allyl glycidyl ether (450.00 mL, 3.792 mol, 22 eq), and succinic anhydride (379.43 g, 3.792 mol, 22 eq) were added to the reactor. The temperature was increased to 80 °C. The monomer conversion was first monitored when the reaction was no longer cloudy, indicating that the succinic anhydride had fully solubilized. Post-purification NMR spectra revealed the following resonance shifts (ppm):1H NMR (600 MHz, CDCl3) 87.30, 5.87, 5.27, 5.19, 4.34, 4.22, 3.99, 3.56, 3.50, 3.47, 2.64, 1.63, 1.38. Post-purification13C-NMR spectra revealed the following resonance shifts (ppm):13C-NMR (600 MHz, CDCh) δ 171.77, 171.50, 134.31, 117.32, 77.35, 77.13, 76.92, 72.31, 70.65, 68.13, 63.03, 29.06, 28.88. Post-purification TGA revealed a Td of 319°C. Post-purification DSC revealed a Tgof -45°C. Post-purification MALDI TOF revealed a Mnof 3600 g / mol.Example 14 Kinetics Studies.

[0291] Polymerization kinetics of PAGES polymers were studied using1H NMR relative integrations of alkyl (-CH2-) protons in the hexanediol initiator (δ = 1.6 ppm) and methylene (- CH2O(C=O)-) protons in the polymer repeat unit (δ = 4.3 ppm) from crude1H NMR samples measured once every 24 hours to monitor changes in degree of polymerization over time. The results are reported in FIG 2.Example 15Photochemical 3D Printing

[0292] 3D printing resins were prepared by mixing ethyl acetate, phenylbis-(2,4,6- trimethylbenzoyl)phosphine oxide (BAPO), 2-hydroxy-4-methoxybenzophenone (HMB), 2, 2,6,6- tetramethyl-l-piperidinyloxy (TEMPO), and tri m ethylolpropane tri s(3 -mercaptopropionate) to purified PAGES polymer. The amount of ethyl acetate added varied for each print (0 wt.% (i.e. no ethyl acetate) to 20 wt.%). BAPO (0.6 wt.%) and HMB (0.4 wt.%) were used in all prints that contained ethyl acetate relative to the mass of the polymer. BAPO (0.5 wt.%) and TEMPO (0.01 wt.%) were used in all solvent free prints relative to the mass of the polymer. The amount of thiol crosslinker added was determined by the desired crosslinking ratio, which is defined as the molar ratio of alkenes in the polymer backbone to thiols in the respective crosslinker. An EnvisionTec D4K Pro DLP 3D printer (λ = 385 nm, 5 mW / cm2, 25-50 μm XY resolution, 25-100 μm Z resolution) was used for this study. Print cure time was determined by cure testing each resin prior to printing. Cure testing was completed by printing four single layer 100 μm thick disks at varying layer print times and measuring the height of the disks. This was repeated until disks approximately 0.4 mm tall were produced. The print time that corresponded to the 0.4 mm tall disks was used as the 100 μm layer cure time for the print. Disk height was measured using an Absolute Digimatic Indicator Series 543. Tensile bars (ASTM D368 Type V, 63.5 x 9.5 x 3.2 mm) and bars (18 x 3.6 x 2.4 mm) were printed and washed using ethyl acetate and isopropanol, submerged in deionized (DI) water, and cured in a B9Creations B9 Model Cure XL UV oven (70 W, 55Hz, λ = 390-420 nm) for 15 minutes. Samples were then dried in a Thermo Scientific Lindberg / Blue M Vacuum Oven at 60 °C for 6 days. The results are reported in FIGS. 19-66 and 79-81.Example 163D Printed Part Shrinkage Studies.

[0293] 3D printed tensile bars were formed from DP65:1, DP95:1, DP165:1, DP1610:1, DP1620:1, and DP9 10:1 using DLP 3D printing and measured using calipers to determine the length, width, and height of each specimen (n=5). Measured dimensions were compared to print dimensions of the STL file input into the printer. Percent difference in each dimension was calculated as the percentage normalized ratio of the measured dimension to the corresponding STL file dimension. Percent shrinkage in each dimension was calculated as 100% difference. The results are reported in FIGS. 79A-C, 80A-C, 81 A-C and Tables 32-34.Example 17Tensile Testing.

[0294] Uniaxial tensile testing was performed (n=5) on 3D printed ASTM D368 Type V tensile bars (63.5 x 9.5 x 3.2 mm) of DP6 5:1, DP95:1, DP165:1, DP1610: 1, DP1620:1, and DP910:1 using a TA Instruments Discovery HR-3 Hybrid Rheometer with tensile clamps. Tensile bar sample edge tabs were fit with sandpaper to prevent slippage during testing. Stress and strain were measured at a clamp separation speed of 10 mm / min. The ultimate tensile strength was determined as the maximum recorded stress value. The strain at break was determined as strain that corresponded to the ultimate tensile strength. The tensile modulus was determined as the slope of the stress-strain curve between 0% and 0.1% strain. The results are reported in FIGS. 19, 23-33, 49C, 49E, 53-57, 59-61, 78.Example 18 Dynamic Mechanical Analysis (DMA).

[0295] Oscillation strain sweeps in tension were performed on 3D printed bar (18 x 3.6 x 2.4 mm) of DP65:1, DP9 5:1, DP165:1, DP1610:1, DP1620:1, and DP9 10:1 to identify the linear viscoelastic region (LVR) for subsequent measurements. The frequency was maintained at 1 Hz while the strain varied from 0.1 to 1%. The LVR was determined as the strain values between which the measured storage modulus remained constant. Oscillation frequency sweeps in tension were performed on 3D printed bars (18 x 3.6 x 2.4 mm) (n=3). The strain was maintained at 0.5% while the frequency varied between 0.1 and 100 Hz. Elongational storage modulus was determined as the storage modulus corresponding to a frequency of 5 Hz. Oscillation temperature ramps were performed on a 3D printed bar (18 x 3.6 x 2.4 mm). The strain was maintained at 0.1% and the frequency was maintained at 1 Hz while the temperature was ramped from -50 °C to 200 °C at a rate of 5 °C / min. Tgwas determined as the temperature corresponding to the maximum tan(8) value. The rubbery modulus (G’ rubbery) was determined as the minimum storage modulus plateau. The molecular weight between crosslinks (Mc) was determined using the following equation where p is the density of the network, R is the universal gas constant, T is the temperature of the onset of the rubbery plateau, G’ rubbery is the rubbery modulus. Density of the network was assumed to be 1 g / cm3for all calculations.The crosslink density (q) was determined using the following equation where Mwis the weight average molecular weight of the polymer calculated via MALDI TOF mass spectrometry and Mcis the molecular weight between crosslinks. (See, e.g., Ahn, D.; Stevens, L. M.; Zhou, K.; Page,Z. A. Additives for Ambient 3D Printing with Visible Light. Advanced Materials 2021, 33 (44), 2104906, the disclosure of which is incorporated herein by reference in its entirety).The results are reported in FIGS. 22, 34-43, 46, 48, 49B, 50-52, 58, 62-63.Example 19Degradation Studies.

[0296] Degradation experiments were conducted on 3D printed bars (n= 5) of DP65: 1, DP95:1, DP165:1, DP1610:1, DP1620:1, and DP910:1 in IM NaOH solution at 37 °C. The bars were weighed and then submerged in 5 mL of solution with the mass being measured at 2, 4, 7, 10, 14, 21, and 28 days. Sample mass was recorded at every time point as both a wet mass immediately after being removed from solution and as a dry mass after being dried in a 60 °C vacuum oven for 2 days. Percentage degradation was determined using the following equation where Wo is the initial dry mass of the sample and Wd is the final dry mass of the sample.The results are reported in FIG. 44 A.Example 20Swelling Studies.

[0297] Swelling experiments were conducted on of DP65:1, DP95: 1, DP165: 1, DP1610:1, DP1620:1, and DP910:1 using 3D printed bars (n=3) in ethyl acetate at room temperature. The bars were weighed and then submerged in 10 mL of solution with the mass being measured after 48 hours. Sample mass was recorded as both a wet mass immediately after being removed from the ethyl acetate and as a dry mass after being dried in a 60 °C vacuum oven for 2 days. Swelling percentage and sol fraction were calculated using the following equations, where Wo is the initial dry mass of the sample, Wd is the final dry mass of the sample, and Wsis the swollen, wet mass immedi ately after being removed from the ethyl acetate.The results are reported in FIGS. 44B, 44C, 45-48, 49F, 49G.Example 21 Micro-Computed Tomography (pCT).

[0298] pCT scans were completed using a Nikon XTH 225 ST instrument. Voxel size was 24.34 μm. The source to object distance was 90.83 mm. The source to detector distance was 746.20. X-ray projections (n = 2500 projections) were taken in a 360 degree scan with an angular step between projections of 0.144 degrees. The x-ray energy was 189 kilovolts (kV). The x-ray flux was 85 microamps (pA). The beam power was 16.1 watts (W). The gain was 24 decibels (dB). Scans were reconstructed in Avizo software. The scans are reported in FIGS. 64B, 64C, 64E, 64F.Example 22Scanning Electron Microscopy (SEM).

[0299] SEM was performed on a Thermo Fisher Scientific Apreo S. Magnification was kept constant at SOX and angles were varied between 5 and -5 degrees in order to image pore spaces precisely. The SEM images may be found in FIG. 65.

[0300] In light of the foregoing, it should be appreciated that the present invention significantly advances the art by providing a solvent-free 3D printable resin that is structurally and functionally improved in a number of ways. While particular embodiments of the invention have been disclosed in detail herein, it should be appreciated that the invention is not limited thereto or thereby inasmuch as variations on the invention herein will be readily appreciated by those of ordinary skill in the art. The scope of the invention shall be appreciated from the claims that follow.

Claims

CLAIMSWhat is claimed is:

1. A solvent-free resin for 3D printing comprising: a linear poly(allyl glycidyl ether succinate) copolymer having a degree of polymerization of from about 2 to about 20; and a multi-functional thiol crosslinker; wherein said solvent free resin has a complex viscosity of from about 0.5 Pa.s to about 20.0 Pa.s.

2. The solvent-free resin of claim 1, wherein the poly(allyl glycidyl ether succinate) copolymer comprises the ring opening copolymerization reaction product of succinic anhydride and allyl glycidyl ether using a mono- or bi-functional alcohol initiator and Mg(BHT)2(THF)2 catalyst.

3. The solvent-free resin of claim 1, wherein the shaped poly(allyl glycidyl ether succinate) copolymer comprises a linear copolymer having two poly(allyl glycidyl ether succinate) chains emanating from a residue of a bi-functional alcohol initiator.

4. The solvent-free resin of claim 1, wherein the linear poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having the formula:where R is a residue of a mono-functional initiating alcohol and x is an integer from 2 to 20.

5. The solvent-free resin of claim 1, wherein the linear poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having the formula:where a is an integer from 2 to 20 and each x is an integer from about 1 to about 10.

6. The solvent-free resin of claim 1, wherein the poly(allyl glycidyl ether succi nate) copolymer is a linear copolymer having a formula selected from:where each x is an integer from about 1 to about 10.

7. The solvent-free resin of claim 1, wherein the poly( allyl glycidyl ether succinate) copolymer has a degree of polymerization of from about 2 to about 20.

8. The solvent-free resin of claim 1, wherein the multi-functional thiol crosslinker has from 2 to 4 thiol functional groups.

9. The solvent-free resin of claim 1, wherein the multi-functional thiol crosslinker is selected from the group consisting of trimethylolpropane tris (3 -mercaptopropionate), bis(3- mercaptopropyl) succinate, pentaerythritol tetrakis(3-mercaptopropionate), isosorbide bis(3- mercaptopropionate), 2,2'-((diisopropylsilanediyl)bis (oxy))bis(ethane-1-thiol), and combinations thereof.

10. The solvent-free resin of claim 1, wherein the multi-functional thiol crosslinker has the formula:

11. The solvent-free resin of claim 1, wherein the multi-functional thiol crosslinker comprises from about 1 weight percent to about 36 weight percent of said solvent-free resin.

12. The solvent-free resin of claim 11, wherein the multi-functional thiol crosslinker comprises from about 8 weight percent to about 12 weight percent of said solvent-free resin.

13. The solvent-free resin of claim 1, comprising about 89 wt.% or more of said poly(allyl glycidyl ether succinate) copolymer.

14. The solvent-free resin of claim 1, wherein a molar ratio of allyl groups on said poly(a11yl glycidyl ether succinate) copolymer to thiol groups on said multi-functional thiol crosslinker is from about 1 : 1 to about 20: 1.

15. The solvent-free resin of claim 1, wherein the molar ratio of allyl groups on said poly(allyl glycidyl ether succinate) copolymer to thiol groups on said multi-functional thiol crosslinker is about 5:1.

16. The solvent-free resin of claim 1, containing 2.0 wt.% or less, preferably 1.0 wt.% or less, and more preferably 0.1 wt.% or less, of a solvent or diluent.

17. The solvent-free resin of claim 1 , further comprising at least one photoinitiator.

18. The solvent-free resin of claim 17, wherein the photoinitiator is phenylbis(2,4,6- trimethylbenzoyl)phosphine oxide (BAPO).

19. The solvent-free resin of claim 1, further comprising a light attenuating agent or photoinhibitor.

20. The solvent-free resin of claim 19, wherein the light attenuating agent or photoinhibitor is oxybenzone.

21. The solvent-free resin of claim 1, further comprising BAPO and oxybenzone.

22. The solvent-free resin of claim 21, further comprising 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO).

23. The solvent-free resin of claim 1, having a complex viscosity of from about 0.5 Pa.s to about lO Pa.s.

24. The solvent-free resin of claim 1, compri sing: from about 80 wt.% to about 99 wt.% of said poly(allyl glycidyl ether succinate) copolymer; from to 1 wt.% to about 20 wt.% of said multi-functional thiol crosslinker, wherein the molar ratio of allyl groups in said polyfallyl glycidyl ether succinate) copolymer to thiol groups in said multi-functional thiol crosslinker is from about 1 : 1 to about 20: 1; and from about 0.1 wt% to about 3 wt.% of a photoinitiator.

25. The solvent-free resin of claim 24, further comprising from about 0.1 wt.% to about 3 wt.% light attenuating agents or photoinhibitors.

26. The solvent-free resin of claim 24 wherein the multi-functional thiol crosslinker is trimethylol propane tris (3 -mercaptopropionate) and the poly(allyl glycidyl ether succinate) copolymer has a formula selected from:

27. A 3D printed polymer structure formed from the solvent-free resin of claim 1 .

28. A linear poly(allyl glycidyl ether succinate) copolymer for use in 3D printing comprising two poly(allyl glycidyl ether succinate) copolymer segments each having a degree of polymerization of from about 2 to about 100 wherein said two poly(allyl glycidyl ether succinate) copolymer segments are joined to each other through the residue of a bi- functional alcohol initiator.

29. The linear poly(allyl glycidyl ether succinate) copolymer of claim 28, wherein the linear poly(allyl glycidyl ether succinate) copolymer comprises the ring opening copolymerization reaction product of succinic anhydride and allyl glycidyl ether using a bi -functional alcohol initiator and Mg(BHT)2(THF)2 catalyst.

30. The linear poly(allyl glycidyl ether succinate) copolymer of claim 28, wherein the linear poly(allyl glycidyl ether succinate) copolymer comprises two poly(allyl glycidyl ether succinate) chains emanating from a residue of a bi-functional alcohol initiator.

31. The linear poly(allyl glycidyl ether succinate) copolymer of claim 28, wherein the linear poly(allyl glycidyl ether succinate) copolymer comprises a poly(allyl glycidyl ether succinate) chain emanating from a residue of a mono-functional alcohol initiator.

32. The linear poly(allyl glycidyl ether succinate) copolymer of claim 28, wherein the linear poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having the formula:where a is an integer from 2 to 20 and x is an integer from about 1 to about 50.

33. The linear poly(allyl glycidyl ether succinate) copolymer of claim 28, wherein the linear poly(allyl glycidyl ether succinate) copolymer is a linear copolymer having a formula selected from:where a is an integer from 2-20 and x is an integer from about 2 to about 50.

34. The linear poly(allyl glycidyl ether succinate) copolymer of claim 28, wherein each of the poly(allyl glycidyl ether succinate) copolymer segments has a degree of polymerization of from about 1 to about 10.

35. A method for making a solvent-free poly(allyl glycidyl ether succinate) resin according to claim 1 comprising:A) preparing a linear poly(allyl glycidyl ether succinate) copolymer having a degree of polymerization of from about 2 to about 20 and a complex viscosity of from about 0.5 Pa.sto about 20.0 Pa.s;B) adding one or more photoinhibitor and one or more photoinitiator; andC) adding a multi-functional thiol crosslinker to the mixture of step B to produce a solvent- free poly(allyl glycidyl ether succinate) resin, wherein the molar ratio of allyl groups in said linear poly(allyl glycidyl ether succinate) copolymer to thiol groups in said multi- functional thiol crosslinker is from about 1:1 to about 20:1.

36. The method of claim 35, wherein the linear poly(allyl glycidyl ether succinate) copolymer has a formula selected from:where a is an integer from 2 to 20 and each x is an integer from about 1 to about 10.

37. The method of claim 35, wherein the photoinitiator is phenylbis(2,4,6- trimethylbenzoyl )phosphine oxide (BAPO).

38. The method of claim 35, wherein the photoinhibitor is at least one of 2,2,6,6-tetramethyl-l- piperidinyloxy (TEMPO) and oxybenzone.

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