Solvent-free synthesis and purification of poly(Β-methyl-Δ-valerolactone)

Abstract

This invention relates to solvent-free synthesis and purification of poly(β-methyl-δ-valerolactone) (sometimes referred to herein as "PβMVL") and variants thereof (e.g., cross linkable, e.g., photo-cross linkable PβMVL's and cross-linked products formed therefrom) as well as related methods of use, compounds and compositions thereof.

Description

[0001]Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 SOLVENT-FREE SYNTHESIS AND PURIFICATION OF POLY(β-METHYL-δ-VALEROLACTONE) CROSS REFERENCE TO RELATED APPLICATION This application claims the benefit of United States Provisional Patent Application No.63 / 669,576, filed on July 10, 2024, which is incorporated herein by reference in its entirety. STATEMENT OF GOVERNMENT SUPPORT This invention was made with government support under FA8650-21-2-5028 awarded by the United States Air Force. The government has certain rights in the invention. TECHNICAL FIELD This invention relates to solvent-free synthesis and purification of, e.g., poly(β- methyl-δ-valerolactone) (sometimes referred to herein as “PβMVL”) and variants thereof (e.g., cross linkable, e.g., photo-cross linkable PβMVL’s and cross-linked products formed therefrom) as well as related methods of use, compounds and compositions thereof BACKGROUND Production of plastics typically uses petroleum-based feedstocks. Polyurethanes (PUs) are petroleum-derived and cannot degrade on reasonable timescales. Polyols, diisocyanates, and diol chain extenders are used in the synthesis of thermoplastic polyurethanes (TPUs). Industrial preparation of TPUs typically proceeds by reacting polyol, diisocyanate, and chain extender simultaneously. SUMMARY Thermoplastic polyurethane-ureas (TPUUs) from bio-based, depolymerizable polyesters may be recycled. This disclosure describes the bulk room temperature polymerization of β-methyl-δ-valerolactone (βMVL) using hydrochloric acid (HCl), as a solution in ether, as an acid catalyst to prepare low molar mass polyols. Production of poly(β- methyl-δ-valerolactone) (PβMVL) typically includes a non-negligible equilibrium monomer concentration ([M]eq) at temperatures at or greater than room temperature. To mitigate the consequences of residual monomer that results from βMVL polymerization strategies including rapid distillation to rid the polymer of residual monomer; sequestration of remaining Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 monomer with diamines to prepare diamidodiols in situ along with the polyol, which can subsequently be used as chain extenders in polyurethane urea syntheses; the copolymerization of βMVL with lactone monomers that exhibit a higher ceiling temperature to prepare copolymers with varying degrees of crystallinity, improved thermal stability, and reduced residual βMVL content, or any combination thereof can be used. The aliphatic polyols can then be used as soft-segments in a one-pot approach to prepare TPUUs by reacting with isophorone diisocyanate and chain extending with water. The resulting TPUUs are tough, elastic materials that can be chemically recycled by depolymerization to βMVL, which can be used to prepare new TPUUs with comparable properties. This disclosure describes one-pot, solvent-free synthesis of low molar mass polyols from lactone-based monomers, and purification of PβMVL via distillation under reduced pressure at 120 °C without significant depolymerization. Solvent-free syntheses are more desirable under the principles of Green Chemistry by removing the environmental impacts and safety concerns associated with using organic solvents. Minimizing the number of steps and reagents for the purification of the polyol is desirable for industrial standards. Using an organic acid catalyst with increased volatility that is active at room temperature and pressure is an improvement from using toxic metal-based catalysts that require high temperatures for activity. Using organic acid catalysts with increased volatility is an improvement from using other organic acids like diphenyl phosphate which, while active at room temperature, typically devolatilize at high temperatures in solvent-free conditions. In another aspect, this disclosure also features cross linkable, e.g., photo cross linkable, PβMVL’s. In some embodiments, said PβMVL’s are provided by contacting a PβMVL described herein (e.g., prepared using any of the methods described herein) with one or more cross-linking agents (e.g., an acrylate-based cross-linking agent, e.g., 2- isocyanatoethyl acrylate). By way of example, this disclosure provides a one-pot, solvent-free synthesis of cross linkable, e.g., photo-cross linkable, PβMVLs. In still another aspect, this disclosure provides cross-linked products formed from said cross linkable, e.g., photo cross linkable PβMVLs. This disclosure also describes related methods of use, compounds and compositions. The details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 BRIEF DESCRIPTION OF DRAWINGS FIG.1 is a reaction schematic illustrating a solvent-free synthesis and purification of poly(β-methyl-δ-valerolactone) (PβMVL) using HCl in ether as a catalyst for ring opening transesterification polymerization (ROTEP). FIG. 2 shows a change in [βMVL] as a function of time at different catalyst loadings at a fixed initial benzene dimethanol (BDM) concentration ([BDM]0). FIG. 3 shows1H NMR spectra showing removal of HCl in ether and residual βMVL monomer by reduced pressure distillation at 120 °C. FIG. 4 shows an effect of βMVL feed content on conversion after polymerization with 1 mol% HCl in ether for 24 h at room temperature. FIG. 5 shows an effect of PβMVL content in copolymer on degradation temperature, as determined by TGA (10 °C min-1ramp rate). FIGS. 6A and 6B show differential scanning calorimetry (DSC) data for copolymers and homopolymers. FIG.6A shows DSC data for PβMVL-co-PCL. FIG.6B shows DSC data for PβMVL-co-PVL. FIG. 7 is a reaction schematic showing synthesis of carbamate end-blocked PβMVL from telechelic PβMVL and cyclohexyl isocyanate. FIG.8 shows1H NMR spectra of successful endblocking after 40 days. FIG.9 shows a reaction schematic of sequestration of βMVL with diamines to form diamidodiols. FIG. 10A-C shows a reaction schematic of a synthesis of thermoplastic polyurethane-ureas (TPUUs) with various polyols. FIG.10A shows polyol C (PβMVL-co-PCL P). FIG. 10B shows polyol S: PβMVL with diamidodiol prepared in situ. FIG. 10C shows polyol D: PβMVL. FIG.11 shows tensile properties of TPUUs. FIG.12 shows DMTA plots of TPUUs. FIG.13 shows hysteresis plots of four TPUUs. FIG. 14 shows a reaction schematic of polyol R reacted with IPDI and chain extended with water. FIG. 15 shows Impact of kobs v. [HCl] for the bulk polymerization of βMVL at room temperature plotted on a linear axis. kobs values obtained from the slopes in FIG.1. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 FIG. 16. Change in [MVL] as a function of time at different catalyst loadings at a fixed [BDM], assuming negligible volume of mixing. Data was fit to early conversions to estimate initial rates. FIG. 17. Impact of kobson [HCl] for the bulk polymerization of βMVL at room temperature plotted on a linear axis. This data was from an initial rates analysis in FIG. S2. FIG. 18. a) First order kinetics fit at different catalyst loadings at a fixed [BDM], assuming negligible volume of mixing. [M]0 = 9.64 and [M]eq was approximated to be 1.04 based on equilibrium data. This data does not fit well to a linear regression indicating a first order analysis is not the best to describe this polymerization. FIG. 19. SEC data from a PMVL polyol before and after 3h distillation at 120 °C to remove 10% remaining BMVL. Mn before distillation was 5.6 kg / mol and after distillation was 5.7 kg / mol, indicating no significant depolymerization. THF mobile phase on an instrument equipped with a MALS detector. FIG. 20.1H NMR spectrum showing long-term instability of vacuum-distilled PβMVL (no catalyst) at room-temperature in a sealed glass vial. After 25 days, more βMVL has reappeared, indicating re-establishment of equilibrium monomer concentration. FIG. 21. Representative1H NMR spectrum of peak assignments for monitoring copolymerization kinetics of βMVL with CL. FIG. 22 shows representative1H NMR spectrum of peak assignments for monitoring copolymerization kinetics of βMVL with VL. FIG. 23. Monomer conversion vs. total conversion for the copolymerization of βMVL and CL. Data were fit to the BSL nonterminal model. FIG. 24. Monomer conversion vs. total conversion for the copolymerization of βMVL and VL. Data were fit to the BSL nonterminal model. FIG.25. Reactivity ratios determined from copolymerizations of a) βMVL and CL or b) βMVL and VL with different initial feed ratios of βMVL. Reactivity ratios were calculated from the Beckingham-Sanoja-Lynd Model (BSL). FIG. 26.1H NMR spectrum showing long-term stability of PβMVL-PCL copolymers (no at room-temperature in a sealed glass vial. After 30 days, no additional βMVL (red) has reappeared, indicating kinetic trapping by end-capping CL repeat units. FIG. 27. Map of PβMVL-co-PCL copolymer structures for a representative 50 chains generated by the SM model for the fβMVL= 0.6 composition. βMVL repeat units are shown in blue and CL repeat units are shown in red. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 FIG. 28. Map of PβMVL-co-PVL copolymer structures for a representative 50 chains generated by the SM model for the fβMVL= 0.6 composition. βMVL repeat units are shown in blue and VL repeat units are shown in red. FIGS.29(a) and 29(b). TGA of a) PβMVL-co-PCL and b) PβMVL-co-PVL copolymers and homopolymers under nitrogen, using a 10 °C min-1ramp rate from room temperature to 550 °C. The insets show the difference in temperatures of 0-5% mass loss. FIG. 30.1H NMR spectrum showing endcapping of PβMVL with phenyl isocyanate, preventing reformation of βMVL monomer. FIG. 31. FTIR spectrum showing successful endcapping of PβMVL with phenyl isocyanate. The peak boxed at 2260 cm-1indicates the NCO peak. FIG. 32.1H NMR spectrum showing successful sequestration of βMVL with Jeffamine EDR-148. FIG. 33.1H NMR spectrum showing sequestration of βMVL with hexamethylene diamine. However, the stability of the polyol decreases over time as seen with the increased content of βMVL after one month. FIG. 34. Thermogravimetric Analysis of four different polyols (copolymer, sequestered, distilled, and recycled). Values are shifted for clarity. Samples were heated from 40 °C to 550 °C at a rate of 10 °C min-1. FIG. 35. Differential scanning calorimetry of four different polyols (copolymer, sequestered, distilled, and recycled). Black triangles denote the glass transition temperature. Values are shifted for clarity. Data were taken from the second heating ramp from -80 to 200 °C at a rate of 10 °C min-1. FIG. 36. FTIR spectrum showing the progression of polyurethane-urea formation of TPUU-C. The peak at 2250 cm-1corresponds to the isocyanate peaks and the peak at 3370 cm-1corresponds to the N-H peaks in the TPUU. CE means after chain extension with water. FIG. 37. FTIR spectrum showing the progression of polyurethane-urea formation of TPUU-S. The peak at 2250 cm-1corresponds to the isocyanate peaks and the peak at 3370 cm-1corresponds to the N-H peaks in the TPUU. CE means after chain extension with water. FIG. 38. FTIR spectrum showing the progression of polyurethane-urea formation of TPUU-D. The peak at 2250 cm-1corresponds to the isocyanate peaks and the peak at 3370 cm-1corresponds to the N-H peaks in the TPUU. (CE means after chain extension with water). FIG. 39. FTIR spectrum showing the progression of polyurethane-urea formation of TPUU-R. The peak at 2250 cm-1corresponds to the isocyanate peaks and the peak at 3370 cm-1corresponds to the N-H peaks in the TPUU. CE means after chain extension with water. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 FIG. 40. Size Exclusion Chromatography of TPUUs and their polyol precursors. Data were taken on an HFIP SEC equipped with RI detector relative to PMMA standards at a flow rate of 0.35 mL min-1. FIG. 41. Thermogravimetric Analysis of TPUUs prepared from four different polyols (copolymer, sequestered, distilled, and recycled). Values are shifted for clarity. Samples were heated from 40 °C to 550 °C at a rate of 10 °C min-1. FIG.42. Differential scanning calorimetry of TPUUs prepared from four different polyols. Black triangles denote the glass transition temperature. Values are shifted for clarity. Data were taken from the second heating ramp from –80 to 200 °C at a rate of 10 °C min-1. FIG.43. GC spectrum of virgin and recycled βMVL. Sample was run on a GC-MS equipped in electrospray mode from 50 to 320 °C at a rate of 20 °C min-1. FIG. 44.1H NMR spectrum of virgin βMVL (bottom) and recycled βMVL recovered from TPUU-D (top). The recovered βMVL contains a small amount of 1,4- butanediol initiator which can be quantified and used for subsequent polymerization. FIG. 45. Size Exclusion Chromatography of recycled TPUU and its polyol precursor made from 50% virgin and 50% recycled βMVL. Taken on an HFIP SEC equipped with RI detector, relative to PMMA standards. FIG.46.1H NMR spectrum of βMVL. Taken in CDCl3 on a 500 MHz Bruker NMR spectrometer. FIG. 47.13C NMR spectrum of βMVL. Taken in CDCl3 on a 500 MHz Bruker NMR spectrometer. FIG. 48.1H NMR spectrum of PβMVL with 3.6 mol% residual βMVL. Diastereotopic protons with different chemical shifts are labelled as x and x’. Taken in CDCl3on a 500 MHz NMR Bruker spectrometer. FIG. 49.1H NMR spectrum of PβMVL-co-PCL (fβMVL = 0.5) with 1.6 mol% residual βMVL. Diastereotopic protons with different chemical shifts are labelled as x and x’. Taken in CDCl3on a 500 MHz NMR Bruker spectrometer. FIG.50.13C NMR spectrum of PβMVL-co-PCL (fβMVL= 0.5). Taken in CDCl3on a 500 MHz NMR Bruker spectrometer. FIG. 51.1H NMR spectrum of PβMVL-co-PVL (fβMVL = 0.5) with 3.2 mol% residual βMVL. Diastereotopic protons with different chemical shifts are labelled as x and x’. Taken in CDCl3 on a 500 MHz NMR Bruker spectrometer. FIG.52.13C NMR spectrum of PβMVL-co-PVL (fβMVL= 0.5). Taken in CDCl3on a 500 MHz NMR Bruker spectrometer. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 FIG.53.1H NMR spectrum of EtDA diamidodiol prepared from EtDA and βMVL. Diastereotopic protons with different chemical shifts are labelled as x and x’. Taken in DMSO- d6 on a 500 MHz Bruker NMR spectrometer. FIG.54.13C NMR spectrum of EtDA diamidodiol prepared from EtDA and βMVL. Taken in DMSO-d6 on a 500 MHz Bruker NMR spectrometer. FIG.55.1H NMR spectrum of Jeffamine diamidodiol prepared from Jeffamine-148 and βMVL. Diastereotopic protons with different chemical shifts are labelled as x and x’. Taken in DMSO-d6on a 500 MHz Bruker NMR spectrometer. FIG. 56.13C NMR spectrum of Jeffamine diamidodiol prepared from Jeffamine- 148 and βMVL. Taken in DMSO-d6on a 500 MHz Bruker NMR spectrometer. FIG. 57.1H NMR spectrum of TPUU-C prepared from a PβMVL-co-PCL copolyol. Integrated peaks were used for hard segment content analyses. Taken in DMSO-d6on a 500 MHz Bruker NMR spectrometer. FIG. 58.1H NMR spectrum of TPUU-S prepared from PβMVL with diamine sequestered βMVL. Integrated peaks were used for hard segment content analyses. Taken in DMSO-d6 on a 500 MHz Bruker NMR spectrometer. FIG. 59.1H NMR of TPUU-D prepared from distilled PβMVL. Integrated peaks were used for hard segment content analyses. Taken in DMSO-d6 on a 500 MHz Bruker NMR spectrometer. FIG. 60.1H NMR of TPUU-R prepared from 50% virgin and 50% recycled PβMVL. Taken in DMSO-d6on a 500 MHz Bruker NMR spectrometer. FIG. 61 shows overlayed 1H NMR spectra of PMVL triol with MVL that is purified via vacuum distillation. FIG. 62 shows overlayed 1H NMR spectra of PMVL with residual MVL that is removed via distillation. FIG. 63 shows sequestration of βMVL using representative diamines to prepare diamidodiols. FIG. 64 shows Overlayed 1H NMR spectra of PMVL with MVL sequestered by ethylene diamine. FIG. 65 shows a one-pot TPU synthesis utilizing diamidodiol sequestration for removal of residual βMVL. FIG. 66 shows Arrhenius analysis of bulk βMVL polymerization with HCl^Et2O catalyst plotted relative to conversion from -11 to 45 °C. Error calculated from standard error in kapp from first-order fitting. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 FIG. 67 shows graphs summarizing dynamic mechanical thermal analyses (DMTA) plots of series with A) diamidodiol loading held constant and PβMVL molar mass varied from 0-35 wt%. B) PβMVL molar mass held constant and diamidodiol loading varied from 0-35 wt%. Samples were heated from -60 to 180 °C at a rate of 5 °C min-1. Storage modulus (E’) is shown in closed circles and loss modulus (E”) is shown in open circles. FIG. 68 summarizes the tensile properties of crosslinked PβMVLs. Samples were extended at a rate of 50 mm min-1. a) Representative stress-strain curves of series with diamidodiol loading held constant and PβMVL molar mass varied from Mn= 5-28 kg mol-1. b) Representative stress-stress curves of series with PβMVL molar mass held constant and diamidodiol loading varied from 0-35 wt%. Elastic 50A processed by the same method (a commercial vat photopolymerization resin) is shown for comparison. c) Hysteresis plots of two crosslinked PβMVLs (top: P-10-23, bottom: P-11-35). Samples were extended to 50% strain for 20 cycles. FIG.69 shows graphs summarizing the suitability of photocrosslinkable PBMVLs for vat photopolymerization applications. a) Steady shear viscosity of materials at 1 s-1and 25 °C before crosslinking as a function of polyol molar mass. FIG.70 shows the change in [βMVL] as a function of time at different temperatures and constant [BDO]0, [βMVL]0, and [HCl]0. Negligible volume of mixing was assumed. FIG. 71 shows that first order kinetic fits at different temperatures with constant [BDO]0, [βMVL]0, and [HCl]0. [M]eq was approximated based on equilibrium data after 24 h. Negligible volume of mixing was assumed. FIG.72 shows stacked1H NMR spectra (CDCl3, 500 MHz, 16 scans, 5 s relaxation delay) of PβMVL polymerization at three temperatures prior to devolatilization of HCl^Et2O, showing an increase in equilibrium monomer concentration with increased polymerization temperature. FIG. 73 shows stacked1H NMR spectra (CDCl3, 500 MHz, 16 scans, D1 = 10 s) of representative synthesis of acrylated PβMVL-based material, including sequestration of residual βMVL by diamine and acrylation by 2-isocyanatoethyl acrylate. FIG. 74 shows differential scanning calorimetry (DSC) data for crosslinked PβMVLs. Samples were heated to 80 °C, cooled to -80 °C, and then heated to 80 °C at a ramp rate of 10 °C min-1. Data shown are taken from the second heat (-80 °C to 80 °C). Endothermic heat flow is upward. Plots are stacked for clarity and glass transitions are indicated with triangles. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 FIG. 75 shows Hysteresis plots of crosslinked materials (a: P-10-0, b: P-10-8, c: Elastic 50A). Samples were extended to 50% strain for 20 cycles at a rate of 50 mm min-1. FIG. 76 shows steady-shear viscosity measurements as a function of shear rate at room temperature (25 °C). Viscosities are measured prior to crosslinking and compared to a commercial resin (Elastic 50A). FIG. 77 shows curing kinetics of crosslinkable resins, shown as normalized modulus as a function of time at room temperature (25 °C). UV light (λ = 365 nm, I = 10 mW / cm2) was turned on at 60 s and remained on for 10 min. FIG. 78 shows that in the recycling of crosslinked PβMV, the additional products remaining in the distillation flask (not pictured) are predicted to include crosslinks comprised of diamidodiol segments and allophanate bonds from free isocyanate. FIG.79 shows the1H NMR spectra (CDCl3, 500 MHz, 16 scans) of virgin βMVL (bottom) and recycled βMVL (top) recovered from crosslinked PβMVL (P-10-8) via distillation. The recovered βMVL contains a small amount of 1,4-butanediol, the initiator from the previous βMVL polymerization. FIG.80 shows the1H NMR spectrum of βMVL (CDCl3, 500 MHz, 16 scans). FIG. 81 shows the1H NMR spectrum of distilled PβMVL (CDCl3, 500 MHz, 16 scans, D1 = 10 s). FIG.82 shows the1H NMR spectrum of acrylated diamidodiol (CDCl3, 500 MHz, 16 scans). FIG.831H NMR spectrum of P-10-0 (CDCl3, 500 MHz, 16 scans, D1 = 10 s). The details of one or more embodiments of the invention are set forth in the accompanying FIGS. 1-83 and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. DETAILED DESCRIPTION This disclosure describes solvent-free polymerization and purification techniques to produce poly(β-methyl-δ-valerolactone) (PβMVL) polyols and variants thereof (e.g., cross- linkable, e.g., photo cross linkable PβMVL’s and cross-linked products formed therefrom and related methods, compounds and compositions). This disclosure further describes producing low molar mass polyols from lactone-based monomers in one reaction vessel substantially without the use of solvent. Purification of PβMVL via distillation under reduced pressure at Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 120 °C without significant depolymerization is disclosed. This disclosure also describes the products of the methods provided herein. PβMVL can be prepared through ring opening transesterification polymerization (ROTEP) of the 6-membered cyclic ester β-methyl-δ-valerolactone (βMVL). βMVL, a recyclable feedstock, can be synthesized from sugar feedstocks, and can be used to replace petroleum-derived polyesters. The metal catalyst tin octoate (Sn(Oct)2) which is active at high temperatures can successfully catalyze the ROTEP of various lactones. In some examples, an organozinc catalyst (e.g., Zn(Oct)2) can be used. βMVL has a low ceiling temperature (Tc = 227 °C) in the neat (i.e., undiluted) state due at least in part to the thermodynamic parameters associated with the ring opening reaction to polymer in the forward (polymerization) direction and the ring closing reaction to monomer in the reverse (depolymerization) direction. Thermodynamics limiting monomer conversion to the polymer can originate at least in part from low ring strain, which can produce a low enthalpic driving force for ROTEP, and the positioning and length of n-alkyl substituents, which exacerbate the typical negative change in entropy upon polymerization of small rings. For exothermic polymerizations, polymer formation is favored at low temperatures. Lower polymerization temperatures typically lead to smaller equilibrium monomer concentrations. The ROTEP of βMVL with various organocatalysts (e.g., diphenyl phosphonic acid (DPP) and triazabicyclodecene (TBD)), which are active at reduced temperatures, have been utilized to ensure reasonably low equilibrium monomer concentrations. While these organocatalysts are active at room temperature and make good candidates for the catalyzed ROTEP of cyclic esters, purifying the resultant polymer typically includes various precipitation steps or catalyst devolatilization at high temperatures. The Brønsted acid catalyst HCl, a low boiling catalyst, is a candidate for the ROTEP of lactones at room temperature. Brønsted acid catalysts can undergo an activated monomer mechanism (AMM), in which the rate is limited by the reaction of the protonated monomer with a nucleophilic propagating chain end stemming from initiation by, for example, and exogenous nucleophile. The polymer produced can be purified under reduced pressure at low temperatures to remove the catalyst, eliminating the use of a solvent for purification. While a low ceiling temperature of βMVL can be useful when designing polymers for chemical recycling, a non-negligible equilibrium monomer concentration ([M]eq) at use temperatures can decrease long-term product stability provided there is a mechanism available for reestablishing equilibrium. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 The present disclosure describes a method of polymerizing the low Tc monomer βMVL which focuses on room temperature ROTEP with low levels of HCl (as a solution in ether) as a catalyst. The use of HCl (as a solution in ether) catalyst provides a solution towards the bulk polymerization and purification of aliphatic polyesters. In this disclosure, the kinetics of polymerization of βMVL with HCl to prepare low molar mass polyols that can be used for the synthesis of TPUUs. This disclosure explores methods to manage [βMVL]eq. In one example, PβMVL can be purified via distillation to devolatilize the remaining monomer without significant depolymerization of the polymer. In a second example, copolymerizing βMVL with more thermodynamically favored lactone monomers, yields copolymers with greater thermal stability and lower [βMVL]eqvalues. In a third example, this disclosure uses the remining βMVL and sequesters it with various diamines to produce reactive diamidodiols in situ. Using the three polyol preparation methods, this disclosure describes the synthesis of TPUUs using isophorone diisocyanate (IPDI) and water as a chain extender. The TPUUs can be chemically recycled to recover βMVL in high yield and high purity. Repolymerization of recycled monomer to make polyols for TPUUs demonstrates recoverable material properties. In another aspect, this disclosure features a polyol substituted with one or more cross- linking agents, e.g., PβMVL substituted with one or more cross-linking agents. For ease of reference, a PβMVL substituted in this manner is sometimes referred to as a “cross linkable PβMV,” e.g., “a photo cross linkable PβMVL.” In some embodiments, the photo cross linkable PβMVLs described herein are provided by contacting a PβMVL described herein (e.g., prepared using any of the methods described herein) with one or more cross-linking agents (e.g., an acrylate-based cross-linking agent, e.g., 2-isocyanatoethyl acrylate). In another aspect, this disclosure provides a one-pot, solvent-free synthesis of photocrosslinkable PβMVLs. In still another aspect, this disclosure provides cross-linked PβMVLs. In some embodiments, the cross-linked PβMVLs described herein are prepared by subjecting the photocrosslinkable PβMVLs described herein to reaction conditions suitable to achieve the desired level of cross- linking (e.g., subjecting the photocrosslinkable PβMVLs to light, e.g., UV light). Cross-linking agents can be selected as desired. Additional examples of cross-linking agents include, without limitation, ethylene glycol di(meth)acrylate and derivatives thereof, methylenebisacrylamide, formaldehyde-free cross linking agents (e.g., N-(1-Hydroxy-2,2-dimethoxyethyl)acrylamide), divinylbenzene and derivatives thereof, methacryloyl chloride, acryloyl chloride, methacrylic anhydride, and acrylic anhydride. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 EXAMPLES This disclosure describes the use of controlled polymerization techniques to produce poly(β-methyl-δ-valerolactone) (PβMVL) polyols. Methods of synthesizing and purifying PβMVL are described herein. Utilizing 1M HCl in ether as a Brønsted acid for the acid-catalyzed ring opening transesterification polymerization (ROTEP) of the lactone monomer β-methyl-δ-valerolactone (βMVL) yields polyols of controlled molar masses. Suitable difunctional initiators can be used if desiring linear difunctional polyols (reaction schematic). A representative reaction scheme is provided below. 61). The HCl and ether can be devolatilized under moderately reduced pressure to obtain pure polyol. Due at least in part to PβMVL having a high monomer concentration (~10 mol%) at equilibrium, removal of remaining monomer can be achieved by distillation under reduced pressure at 120 °C for 3 h, at which point the remaining monomer content is typically at or below 1% as seen by1H NMR spectroscopy in (FIG.62). A method for removing monomer includes sequestration using diamines to produce diamidodiols (see FIG. 63 and FIG. 64). The reactive diamidodiol now dissolved in the polymer can be used as a chain extender for the synthesis of thermoplastic polyurethanes (see FIG. 65). The synthesis can be applicable to a variety of lactone monomers to prepare low molar mass polyols. A range of lactones can be used to produce polyols. Initiator loadings can be varied to obtain polyols of ranging molar masses. Materials of molar masses <10,000 g / mol are typically used. A variety of diamines are suitable for the diamidodiol synthesis. A diamine soluble in the polymer could be chosen to produce a solvent-free synthesis. Materials. Hexafluoro-isopropanol, chloroform, methanol, and tetrahydrofuran were obtained from Fisher Scientific and used without any further purification. 1,4-benzene dimethanol was obtained from Sigma-Aldrich and recrystallized 3x in toluene and dried in vacuo to obtain white crystals.1,4-butanediol was obtained from Sigma-Aldrich and dried over 4Å molecular sieves in the vacuum oven at 60 °C and stored in a desiccator. Jeffamine EDR- 148 was obtained from Huntsman and used as received. All other reagents and solvents were Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 obtained from Sigma-Aldrich and used without purification unless otherwise noted. β-Methyl- δ-valerolactone was prepared according to literature and was distilled prior to usage. Characterization NMR Spectroscopy:1H and13C nuclear magnetic resonance (NMR) spectra were obtained in CDCl3 and DMSO-d6 for TPUUs and were obtained on a 500 MHz Bruker Advance III spectrometer. Number average molar masses of polymers were obtained by end-group analysis. Size exclusion chromatography: Data for the hydroxy-terminated PβMVL homopolymers and copolymers were obtained on an Agilent Infinity 1260 series HPLC system equipped with a Wyatt multiangle laser light scattering detector and Wyatt diffractive refractive index detector through 3 Styragel HR columns at 35 °C with a tetrahydrofuran mobile phase and flow rate of 1 mL min-1. A concentration of 4−5 mg mL-1was used for each sample. The average molar mass values and molar mass distribution for each polymer was determined using a 100% mass recovery method that uses an “in-line” method using the area of the total area of the RI signal for samples of a known concentration to determine the dn / dc of the polymer. Data for the PβMVL prepolymers and TPUUs were obtained on a Tosoh EcoSEC system equipped with a refractive index detector in a hexafluoroisopropanol mobile phase and a flow rate of 0.35 mL min-1. Molar masses were determined using PMMA standards. Fourier transform infrared spectra (FTIR): Data were obtained on a Bruker Alpha Platinum spectrometer equipped with a diamond crystal in attenuated total reflection (ATR) mode. A resolution of 4 cm-1and 32 scans were done for each sample. Gas chromatography- mass spectrometer (GC-MS): Data were obtained on an Agilent 7200 GC / QTOF-MS equipped with chemical ionization. Thermogravimetric analysis (TGA): Measurements were performed on a TA Instruments Q500 Analyzer. Samples were heated from room temperature to 550 °C at a rate of 10 °C min-1under nitrogen atmosphere. A typical sample size was 5–10 mg. Differential scanning calorimetry (DSC): Measurements were performed on a TA Instruments Discovery 2500 differential scanning calorimeter. Samples were analyzed in hermetically sealed T-Zero aluminum pans (2–8 mg). Homopolymer and copolymer samples were heated to 100 °C at 10 °C min-1for the first cycle and subsequently cooled to -80 °C at 10 °C min-1followed by a second heat cycle to 100 °C at 10 °C min-1. TPUU materials were heated to 200 °C at 10 °C min-1for the first cycle and subsequently cooled to -80 °C at 10 °C min-1followed by a second heat cycle to 200 °C at 10 °C min-1. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 Material Processing: TPUU materials were melted processed on a hot press at 160 °C for 2 min then pressed at 160 °C for 2 min at 136.1 kg (300 lbs.) followed by 2 min at 1360.8 kg (3000 lbs.). The samples were rapidly quenched to room temperature. The resultant materials appeared clear and colorless. Dynamic mechanical thermal analysis (DMTA): Experiments were conducted on a TA-instruments RSA-G2 analyzer with rectangular shaped samples in a tensile geometry. Samples were cut from films directly with a thickness of approximately 0.25 mm, a gauge length of approximately 7 mm, and a gauge width of approximately 3 mm. Experiments were conducted under nitrogen atmosphere. For DMTA experiments, samples were cooled to -80 °C with liquid nitrogen and the axial force was adjusted to 0.0 N to ensure no buckling. Once at - 80 °C, the axial force was set to 0.10 N of tension. Samples were heated at a rate of 5 °C min–1to 200 °C with an oscillatory strain of 0.05% and an angular frequency of 6.28 rad s–1(1 Hz). Uniaxial Tensile Testing: A Shimadzu Autograph AGS-X series instrument was used to conduct uniaxial extension and hysteresis tests on the TPUUs at room temperature. Samples were placed in flat grips and sandpaper was used to prevent slipping. Samples were extended at a rate of 50 mm min-1until material failure. The extension experiments were performed with 5 replicates per sample. The Young’s modulus was calculated using a linear fit from 0-1% strain. For hysteresis experiments, one dogbone of each sample was subjected to cyclical loading (50% strain) and unloading for 20 cycles. Noisy data were smoothed using a smoothing function in Origin. Methods Synthesis of β-Methyl-δ-valerolactone: A 500 mL 3 neck round bottom flask, was fitted with a reflux condenser connected to an air bubbler, a thermometer, and a septum. 3- methyl-1,5-pentanediol (110 g, 0.93 mol) and copper chromite (5.8 g, 0.02 mol) were added to the flask. The flask was placed on a heating block and heated to 200 °C until hydrogen evolution slowed by the air bubbler. The reaction was then cooled to room temperature and βMVL was distilled directly from the crude mixture. βMVL was then dried over calcium hydride and distilled a second time to obtain pure βMVL in >80% yield (90 g).1H NMR (500 MHz, CDCl3) δ 4.49–4.35 (m, 1H, –O–CH2–), δ 4.30–4.19 (m, 1H, –O–CH2–), 2.75–2.59 (q, 1H, –C=O–CH2–), 2.18–2.02 (m, 2H, –CH2–CH2–CH–), 1.98–1.87 (m, 1H, –C=O–CH2–), 1.58–1.43 (m, 1H –CH2–CH–), 1.11-0.96 (d, 3H, CH3–CH–). Synthesis of PβMVL polyols: In an inert atmosphere glovebox, diol (1,4- butanediol or 1,4-benzenedimethanol) (360 mg or 552 mg, 4 mmol for target Mn= 2.5 kg / mol) was added to an oven-dried Schlenk adapted two-neck round bottom flask with a magnetic stir Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 bar. The initiator was dissolved in monomer (βMVL) (10 g, 88 mmol). The ratio of alcohol initiator to monomer was varied to obtain different target molar masses. The flask was sealed and removed from the glovebox, before attaching a vacuum line and evacuating / backfilling the arm of the flask 3x with an inert gas such as argon or nitrogen.1M HCl in ether (0.5 mol% to monomer; 0.44 mL, 0.44 mmol) was added to the flask under positive pressure of inert gas. The reaction was left to stir at room temperature until the reaction approached equilibrium as found by1H NMR spectroscopy (typically 10-13% βMVL remaining depending on the specific room temperature), after around 120 min (though the reaction could proceed from 30 min to run overnight, depending on catalyst concentration). Note that the reaction stopped stirring after several minutes for 6 kg / mol molar mass targets at room temperature. Aliquots for kinetics were taken under positive pressure of inert gas and quenched in CDCl3 with pyridine for1H NMR spectroscopy. The crude polymer was placed under vacuum at 45 °C for 2 h to completely devolatilize the HCl and ether. The remaining polymer contained around 8-12% monomer and was used for subsequent experiments. For removal of remaining monomer without depolymerizing the polymer, a short path distillation apparatus was used to distill off residual βMVL at 120 °C under reduced pressure (50–200 mTorr) for 3 h. Note, insulating the round bottom and distillation apparatus with glass wool and aluminum foil and cooling the receiving flask with an ice bath aids in the distillation process. 1H NMR (500 MHz, CDCl3) δ 4.24–4.06 (m, 2H∙n, CH2–CH2–O–), 3.78–3.64 (m, 1H∙n, –CH2–OH), 2.40–2.29 (m, 1H∙n C=O–CH2–), 2.34–2.16 (m, 1H∙n C=O–CH2–) 2.16– 2.07 (m, 1H∙n, –CH2–CH–), 1.78–1.66 (m, 1H∙n, –CH2–CH2–CH–), 1.60–1.46 (m, 1H∙n, – CH2–CH2–CH–), 1.11–1.08 (d, 3H∙n, –CH–CH3). Preparation of Diamidodiols from βMVL and diamines: For PβMVL containing 8-12% MVL, a diamine (ethylene diamine EtDA or Jeffamine-148) was added to the vessel such that the ratio of amine functional groups to βMVL was at least 1:1 and the reaction was left to react at 45°C until all the βMVL had been sequestered by diamine into diamidodiol as monitored by1H NMR spectroscopy. EtDA diamidodiol:1H NMR (500 MHz, DMSO-d6) δ 7.93–7.65 (s, 2H, –NH–), 4.38–4.28 (t, 2H, –OH), 3.47–3.35 (m, 4H, –CH2–CH2–OH), 3.34–3.01 (t, 4H, –NH–CH2–), 2.10–2.01 and 1.89–1.81 (m, 4H, –C=O–CH2), 2.00–1.89 (m, 2H, –CH–CH2), 1.48–1.18 (m, 4H, –CH2–CH2–CH–), 0.89–0.78 (d, 6H, –CH3). Jeffamine diamidodiol:1H NMR (500 MHz, DMSO-d6) δ 7.93–7.70 (s, 2H, –NH– ), 4.41–4.25 (t, 2H, –OH), 3.53–3.47 (s, 4H, –NH–CH2–CH2–), 3.47–3.34 (m, 8H, –CH2–OH and –CH2–CH2–O–), 3.24–3.12 (m, 4H, –CH2–NH–), 2.14–2.00 and 1.90–1.80 (m, 4H, –CH2– Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 C=O), 2.00–1.90 (m, 2H, –CH–CH2–), 1.50–1.18 (m, 4H, –CH2–CH2–CH–), 0.91–0.76 (d, 6H, –CHbh3) Synthesis of PβMVL copolymer polyols: To a two neck round bottom flask was added 1,4-benzenedimethanol as an initiator in an inert atmosphere glovebox. The initiator was dissolved in monomer (βMVL and CL or VL) with a magnetic stir bar. The ratio of βMVL to comonomer was varied to target different copolymer compositions. The flask was sealed and removed from the glovebox before adding 1M HCl in ether (1 mol% to monomer for βMVL- CL copolymerizations and 0.5 mol% to monomer for βMVL-VL copolymerizations) under positive pressure of inert gas. For kinetics experiments, aliquots were taken at desired timepoints under positive pressure of inert gas, quenched with pyridine in CDCl3, and analyzed via1H NMR spectroscopy. Once the polymerization approached equilibrium by1H NMR spectroscopy, the crude polymer was placed under vacuum at 45 °C overnight to completely devolatilize the HCl and ether. PβMVL-co-CL1H NMR (500 MHz, CDCl3) δ 4.20–4.00 (m, 2H∙n + 2H∙m, –CH2– O–), 3.74–3.58 (m, 2H, –CH2–OH), 2.43–2.25 (m, 1H∙n + 2H∙m, –C=O–CH2–), 2.23–2.00 (m, 2H∙n, –C=O–CH2–and –CH–CH3–), 1.79–1.46 (m, 2H∙n + 4H∙m, –CH2–CH2–O– and –C=O– CH2–CH2–), 1.45–1.30 (m, 2H∙m, –CH2–CH2–CH2–O–), 1.01–0.94 (d, 3H∙n, –CH3). PβMVL-co-VL1H NMR (500 MHz, CDCl3) δ 4.20–4.01 (m, 2H∙n + 2H∙m, –CH2– O–), 3.72–3.59 (m, 2H, –CH2–OH), 2.43–2.03 (m, 2H∙n + 2H∙m, –C=O–CH2–), 1.76–1.62 (m, 1H∙n, –CH–CH3–), 1.61–1.45 (m, 2H∙n + 4H∙n, –CH2–CH2–O– and –C=O–CH2–CH2–), 1.04– 0.93 (d, 3H∙n, –CH3). Synthesis of PβMVL TPUUs: A three neck round bottom flask containing PβMVL was cycled under vacuum and inert atmosphere 3x in the Schlenk line and placed under inert atmosphere, before attaching a mechanical stirrer and heating to 65 °C. To the PβMVL flask, 1,8-Diazabicyclo(5.4.0)undec-7-ene (DBU) then isophorone diisocyanate (IPDI) were added. The reaction was left to stir for 1 h in vacuo, upon which the viscosity of the mixture increased. Water was added dropwise after 1 h, resulting in a significant increase in mixture viscosity and opacity as well as bubbling from CO2 evolution. The reaction was stirred until completion as monitored by the disappearance of the NCO stretching peak in the in-situ ATR-FTIR spectrum, at approximately 24 h. The TPUU was removed from the flask, which may be aided by swelling in chloroform and dried in vacuo at 100 °C for 24 h to devolatilize DBU and remove any added solvent. 1H NMR (500 MHz, DMSO-d6) δ 7.56-6.42 and (m, 2H∙m, C=O-NH-CH; CH2- NH-C=O), 6.03-5.27 (m, 2H∙m, -C-CH2-NH-C=O-) 4.38-3.85 (m, 2H∙n, CH2-CH2-O-) 3.73- Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 3.50; 2.84-2.61 (m, 2H∙m, NH-CH-; CH-CH2-C(CH3)2-), 2.42-2.22 and 2.19-2.07 (m, 2H∙n, C=O-CH2-CH-), 2.04-1.88 (m, 1H∙n, -CH2-CH-CH3), 1.72-1.52 and 1.52-1.37 (m, 2H∙n CH- CH2-CH2-), 1.52-1.37 (m, 4H∙m, CH-CH2-C-CH3(CH2)- and -C(CH3)2-CH2-C-), 1.15-0.61 (m, 3H∙n and 9H∙m, CH2-CH(CH3)-CH2; CH2-C(CH3)2-CH2; CH2-C(CH3)(CH2)2-). Recycling of βMVL-based TPUUs: TPUU containing PβMVL was cut into pieces and placed in a one neck round bottom flask with a stir bar. Sn(Oct)2(0.5 mol% to βMVL monomer in TPUU) was added to the flask. βMVL monomer was distilled from the mixture in vacuo at 120 °C for 3 h. Reaction completion was determined by gravimetric analysis of the receiving flask over time and yield was 90%. Material collected in the receiving flask was analyzed by1H NMR spectroscopy and GCMS to determine βMVL purity. βMVL containing diol initiator was subsequently repolymerized by adding additional initiator as necessary to achieve the desired molar mass, as well as HCl in ether catalyst using the previously described method, which could be quantified by1H NMR spectroscopy. Table S1. Summary of PβMVL homopolymer and copolymer data. SampleaMna(kg / mol) Mnb(kg / mol) Đ % βMVL (at [M]eq)PβMVL(8.5) 4.1 13.8 1.3 8.5 PβMVL(21.4) 5.4 7.0 1.3 9.2 PβMVL(43.8) 4.3 6.8 1.2 10.3 PβMVL(87.6) 4.9 6.5 1.1 6.3 PβMVL(E)no - 36 1.6 22 initiator PβMVL(F) 57 36 1.2 5.5 PβMVL-co- 6.5 6.6 1.2 1.9 PCL(0.27) PβMVL-co- 5.6 6.4 1.2 1.9 PCL(0.41) PβMVL-co- 5.7 6.3 1.2 2.4 PCL(0.51) PβMVL-co- 5.8 6.1 1.2 2.7 PCL(0.62) PβMVL-co- 6.0 6.3 1.1 4.9 PCL(0.72) PβMVL-co- 5.1 5.5 1.4 9.1 PVL(0.23) PβMVL-co- 5.6 6.7 1.2 9.3 PVL(0.38) PβMVL-co- 4.9 6.2 1.2 9.4 PVL(0.49) Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 PβMVL-co- 4.6 5.2 1.1 9.4 PVL(0.60) PβMVL-co- 5.3 6.0 1.4 9.6 PVL(0.69)aObtained by end-group analysis via1H NMR spectroscopy. Parenthetical number of copolymer samples refers to the molar fraction of βMVL. For PβMVL homopolymers, the number in parentheses refers to the mmol HCl catalyst loadings (1, 0.5, 0.25, and 0.1 mol% HCl catalyst loadings, respectively). PβMVL homopolymer E refers to a polyol with 1 mol% catalyst and no initiator and polymer F refers to a polyol prepared with 1 mol% catalyst targeting 100 kg / mol based on initiator concentration.bObtained by SEC equipped with MALS detector. Derivation of Empirical Rate Equation (full kinetic analysis) The empirical rate equation for the polymerization of βMVL can be expressed in terms of the reactive species, as follows: ^^^ ൌିௗ^ఉெ^^^ ௗ௧ൌ ^^^^^^^^^^௫^^^^^^^^^^௬^^^^^^^^௭ (1)We defined end) for all us a ^^ᇱ ൌ ^^^^^^^^^^௭ (2)Thus, the empirical rate expression can be re-written as: ିௗ^ఉெ^^^ᇱ ௫௧^ ^௬ௗൌ ^^ ^^^^^^^^ ^^^^^^^^ (3)We also reasonably define a combined observed rate constant: ^^^^^ ൌ ^^ᇱ^^^^^^^^௫ (4)Thus, the empirical rate expression can be re-written as: ିௗ^ఉெ^^^ൌ ^^ ^^^ ^௬ௗ௧^^^ ^^^^^^ (5)Under the four versus time data suggest that the rate expression is zero order in [BMVL]. Thus, the value of y in equation (5) is assumed to be 0 (i.e., zero-order dependence on [BMVL]). The values of the observed rate constant kobsat the four different [HCl] upon fitting to 70% BMVL conversion are given in Table S2: Table S2: Rate data for ROTEP of βMVL at different concentrations of HCl Polymer kobs [HCl] [BDM] Mnb(M min-1) (mmol) (mmol) (kg / mol)at1 / 2(min) PβMVL 0.146 8.5 167 5.4 25 PβMVL 0.197 21.4 167 5.2 18.8 PβMVL 0.450 43.8 167 5.5 8.9 Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 PβMVL 0.673 87.6 167 5.2 5.5aObtained from end group analysis via1H NMR spectroscopybTime required for 50% conversion calculated using equation t1 / 2= [M]0 / (2kobs) where [M]0= 9.64 M To estimate k’ and the order in [HCl] we plotted kobs as a function of [HCl]. The linearity of the plot is consistent with a first order dependence in [HCl] (FIG. S1). This analysis gave a k’ ≈ 6.9 min–1. FIG.15 shows the impact of kobsv. [HCl] for the bulk polymerization of βMVL at room temperature plotted on a linear axis. kobs values obtained from the slopes in FIG.1. FIG.16 shows the change in [MVL] as a function of time at different catalyst loadings at a fixed [BDM], assuming negligible volume of mixing. Data was fit to early conversions to estimate initial rates. FIG. 17 shows the impact of kobs on [HCl] for the bulk polymerization of βMVL at room temperature plotted on a linear axis. This data was from an initial rates analysis in FIG. 16. FIG.18 shows a) First order kinetics fit at different catalyst loadings at a fixed [BDM], assuming negligible volume of mixing. [M]0 = 9.64 and [M]eq was approximated to be 1.04 based on equilibrium data. This data does not fit well to a linear regression indicating a first order analysis is not the best to describe this polymerization. FIG. 19 shows SEC data from a PMVL polyol before and after 3h distillation at 120 °C to remove 10% remaining BMVL. Mn before distillation was 5.6 kg / mol and after distillation was 5.7 kg / mol, indicating no significant depolymerization. THF mobile phase on an instrument equipped with a MALS detector. FIG.20 shows a1H NMR spectrum showing long-term instability of vacuum-distilled PβMVL (no catalyst) at room-temperature in a sealed glass vial. After 25 days, more βMVL has reappeared, indicating re-establishment of equilibrium monomer concentration. Copolymerization kinetics: Monomer conversion: Monomer conversion was determined by monitoring monomer and polymer peak intensities over time. The per-proton integrations for each species in the PβMVL-co-PCL copolymerization were calculated from the following peaks shown in FIG. 21 [[S7]]: βMVL (δ1.04-1.11 ppm, d, J = 6.2 Hz, 3H) = ^ ^δ ^1.04 െ 1.11^ ൌ^ ଷ^ peak aPβMVL (δ0.95-1.00 ppm, d, J = 6.6 Hz, 3H) ^ ଷ^ peak dCL = ^^^ δ ^4.19 െ 4.33^ െ^ ^δ ^1.04 െ 1.11^^ ൌ^^^peak b, c െ^ ଷ^ peak a^ Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 PCL = ^δ ^3.98 െ 4^ ^ ^ ଶ^ .18^ െଷ^ δ(0.95-1.00) =ଶ^ peak e,f െଷ^ peak dFIG.21 shows representative1H NMR spectrum of peak assignments for monitoring copolymerization kinetics of βMVL with CL. The per-proton integrations for each species in the PβMVL-co-PVL copolymerization were calculated from the following peaks shown in FIG.22 [[S8]]: βMVL (δ1.04-1.11 ppm, d, J = 6.2 Hz, 3H) = ^ ^ ଷ^ δ ^1.04 െ 1.11^ ൌଷ^ peak a= = ^ ^ ^ ^c FIG. 22 shows representative1H NMR spectrum of peak assignments for monitoring copolymerization kinetics of βMVL with VL. Kinetic fitting: Using OriginLab software, the kinetic data were fit to the Beckingham- Sanoja-Lynd (BSL) nonterminal model: ^^^୭^ୟ୪ ൌ 1 െ ^^^^ ^1 െ ^^^^ െ ^1 െ ^^^^ ^^1 െ ^^ ^^^ ಳ1 ^^^^ ^1 ^^^^^ಲ ^1 ^^^^ ^^1 ^^^^where ptotal is the total of monomers A and B (ptotal= (pA+ pB) / 2), fA0is the initial feed ratio of monomer A, and rAand rBare the reactivity ratios of monomers A and B (where rA = 1 / rB). The suitability of the kinetic model for the data may be assessed by varying the copolymerization feed compositions and comparing the calculated reactivity ratios. The variation in reactivity ratios across feed compositions suggests that the nonterminal model may not fully describe the copolymerizations,2particularly for the PβMVL-co-PCL copolymers in which the reversible monomer is more kinetically active and present at the chain end when the irreversible comonomer is added. Thus, the copolymerization kinetic data (initial monomer and initiator concentrations and zero-order kinetic rate constants) for a representative experiment were fit to the stochastic model (SM) developed by Kuehster et al., which accounts for the reversible propagation of βMVL during the copolymerization.3We assumed only βMVL exhibited reversibility. A copolymerization with high initial loading of βMVL (fβMVL= 0.6) was selected for the stochastic model to allow for verification of the kinetic rate constants by Kuehster et al.’s related simplified deterministic model (SDM). The SDM extracts rate information directly from experimental data by assuming the only significant depolymerization reaction is that of the slower monomer from a chain end of itself. This assumption is valid for Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 βMVL-VL copolymerizations, in which the reversible βMVL monomer is added slower at higher overall conversions, but not for βMVL-CL copolymerizations, in which the reversible βMVL monomer is added faster at lower overall conversions, making depolymerization of βMVL from βMVL and CL chain ends relevant. Table S3. Summary of copolymerization reactivity ratios for experiments with varying initial loadings of βMVL and CL comonomers. The kinetic data were fit to the Beckingham-Sanoja- Lynd (BSL) nonterminal model and, for a representative trial, a stochastic model (SM). fβMVLrβMVLrCLModel 0.25 4.8 ± 0.3 0.42 ± 0.06 BSL 0.40 4.1 ± 0.4 0.38 ± 0.06 BSL 0.50 4.8 ± 0.5 0.43 ± 0.05 BSL 5.9 ± 0.6 0.44 ± 0.05 BSL 0.60 7.06 0.14 SM 0.75 16.7 ± 2.9 0.25 ± 0.01 BSL Table S4. Summary of copolymerization reactivity ratios for experiments with varying initial loadings of βMVL and VL comonomers. The kinetic data were fit to the Beckingham- Sanoja-Lynd (BSL) nonterminal model and, for a representative trial, a stochastic model (SM). fβMVLrβMVLrVLModel 0.25 0.55 ± 0.04 1.65 ± 0.02 BSL 0.40 0.61 ± 0.02 1.60 ± 0.04 BSL 0.50 0.60 ± 0.02 1.54 ± 0.04 BSL 0.63 ± 0.02 1.44 ± 0.05 BSL 0.60 0.57 1.71 SM 0.62 ± 0.03 1.53 ± 0.05 BSL Homopolymerization of βMVL. The ring opening transesterification polymerization (ROTEP) of βMVL was conducted in bulk at room temperature according to the conditions listed in the reaction schematic shown in FIG.1. HCl in diethyl ether (1 M) was chosen for its room temperature activity and high volatility (boiling point of diethyl ether is 34.6 °C; boiling point of HCl is –85 °C). Polymerization was initiated with a difunctional initiator benzene dimethanol (BDM) to produce linear hydroxy telechelic polymers with target molar masses depending on the initial hydroxyl group [OH]0 concentration. In a control experiment in which no initiator was used, 0.5 mol% HCl (delivered as a solution in diethyl ether) was mixed with neat βMVL, where the initial βMVL concentration ([βMVL]0) was 9.64 M, for one week yielding Mn = 36 kg / mol based on SEC analysis for the product PβMVL. In some examples, the initial βMVL concentration ([βMVL]0) ranges from a Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 concentration of about 5M to about 15 M. Subsequent control experiments targeting 50 kg / mol PβMVL yielded moderate molar masses with a limit around 13 kg / mol by SEC analysis. HCl performs as a catalyst for the controlled preparation of low molar mass (<10 kg / mol) polyols. A series of kinetics experiments was conducted, targeting a specific low molar mass polyol to determine the rates of polymerization at different catalyst loadings. The kinetics of homopolymerization at a fixed [βMVL]0 = 9.64 M and initial benzene dimethanol (BDM) concentration ([BDM]0) = 0.167 M with different initial catalyst concentrations [HCl]0 is shown in FIG.2. The data was fit to 70% conversion. Negligible volume of mixing was assumed. The conditions were chosen to target a PβMVL molar mass of about 6 kg / mol considering the expected equilibrium concentration of βMVL. Monomer conversion was monitored by1H NMR spectroscopy through aliquots taken from the polymerization at designated timepoints and quenched with dilute pyridine in deuterated chloroform to neutralize the acid catalyst. Polymerizations were carried out to equilibrium, about 90% conversion in all cases (requiring < 90 min at the lowest catalyst concentration explored). A negligible molar volume of mixing of monomer in polymer to calculate intermediate βMVL concentrations was assumed. The decrease in monomer concentration appeared linear in time and thus were fit accordingly up to about 70% conversion. The slopes of the lines in FIG.2 correspond to the observed zero-order rate constants kobs (M min-1) at each initial catalyst concentration at these specific initial conditions (i.e., [BDM]0=0.167 M, RT). While the zero-order kinetic analysis gives a good fit, the data was also analyzed using initial rates and first-order analyses (FIGS.16-18). A complete empirical rate equation is described herein. Based on the data, we concluded a first order dependence in HCl concentration (Exhibit 1, FIG.15 and Table S2). The rate of polymerization for βMVL at room temperature when using [BDM]0= 0.167 M (e.g., targeting a PβMVL molar mass of about 6 kg / mol) can be approximated by Equation 1 with k’ = 6.9 min-1: ^^^ ൌିௗ^ఉெ^^^ൌ ^^′^^^^^^^^^^^^^^^^^^^^ ൌ ^^ᇱ^^^^^^^^ (1) Deviation from zero-order kinetics in [βMVL] at higher conversations suggest some competing contributions from protonation and deprotonation equilibria with both the monomer and backbone esters. The data support achievement of equilibrium at the targeted molar masses in as little as 20 min at room temperature using 0.3 wt% HCl. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 Purification of the homopolymers was conducted under reduced pressure at lower temperatures to devolatilize the catalyst prior to distillation at 120 °C under reduced pressure to remove remaining βMVL. In some examples, devolatilizing the catalyst occurs at 45 °C under a reduced pressure of 26,664.5 Pa (200 mTorr). In some examples, distillation occurs at 120 °C at 26,664.5 Pa (200 mTorr). The polymer typically contained < 2 wt% monomer and in the best case < 0.5% monomer as determined by1H NMR spectroscopy (FIG.3). Size exclusion chromatography (SEC) and1H NMR of the polymer before and after distillation confirmed no significant indicating success at a solvent-free purification method (FIG.19). The PβMVL at room temperature showed a re- establishment of equilibrium monomer concentration after 25 days at room temperature in a capped glass vial. FIG. S6 shows the growth of monomer methyl βMVL peaks at 1.1 ppm in a PβMVL homopolymer of Mn= 2000 g / mol. The monomer concentration increased from 1.8% to 4.7 wt% over the period, supporting re-establishment of the equilibrium monomer concentration at room temperature over a period of months. Copolymerizations of βMVL with γ-valerolactone and ε-caprolactone. Copolymerization with comonomers that are more thermodynamically driven to polymerize can reduce total residual monomer content at the end of the polymerization. In some examples, the reaction mixture includes one or more additional lactones, and further includes copolymerizing the βMVL with the one or more additional lactones to yield a copolymer. The one or more additional lactones can include δ-valerolactone, ε-caprolactone, or a combination thereof. Copolymerizations of βMVL with δ-valerolactone (VL) and ε- caprolactone (CL) were explored due at least in part to βMVL, VL, and CL having similar enthalpies of polymerization and lacking the entropic penalty that is typically associated with ring-opening of cyclic esters containing pendant alkyl groups. The copolymerization experiments were conducted using the same conditions as the βMVL homopolymerization (though a reduced catalyst loading was used for βMVL-VL copolymerizations due to faster reaction kinetics), and feed ratios of comonomers were varied from 25% to 75 mol% βMVL. A summary of copolymer data is given in Table S1 and monomer conversion versus total conversion is also given in FIGS.23-24 which were fit to the Beckingham-Sanoja-Lynd model (BSL) to give an estimate of the inherent reactivity ratios at fβMVL= 0.5: rβMVL= 4.8 and rCL = 0.43 for βMVL-CL copolymerizations and rβMVL = 0.60 and rVL = 1.54 for βMVL- VL copolymerizations. The nonterminal BSL model assumes that the rate of monomer incorporation depends on the monomer rather than chain end identity and is consistent with the proposed activated monomer mechanism, in which reactivity is largely determined by Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 monomer basicity. BSL and other simplified models using the copolymer equation do not account for reversible propagation. A stochastic model, using monomer and initiator concentrations and zero-order kinetic rate constants, was used to calculate reactivity ratios with reversibility considered (Tables S3–S4). The two models generated similar reactivity ratios (e.g., when the reversible monomer was present at the chain end as is the case for βMVL-VL copolymerizations). Copolymerizations exhibited a gradient behavior, as indicated by the reactivity ratios (rA> 1 > rB) shown in FIG.25, in which the less kinetically active monomer was located towards the chain ends. The ability of copolymerization to stabilize PβMVL was determined by the kinetic profile of the copolymerization. FIG.4 shows an effect of βMVL feed content on conversion after polymerization with 1 mol% HCl in ether for 24 h at room temperature. As shown in FIG.4, increased feed ratio of the comonomer resulted in greater conversion of βMVL. The CL comonomer, with a slower rate of polymerization relative to βMVL, added more monomer units near the chain ends. This “end-capping” of βMVL repeat units helped prevent depolymerization by chain-end backbiting and reduced residual βMVL and CL content to as low as 1.3 wt% and ~0 wt%, respectively. The monomer content did not change after leaving the copolymer at room temperature for 1 month as shown in FIG.26. This gradient composition has been observed in copolymers of α-methylene-δ-valerolactone and ε-caprolactone, with reactivity ratios of rαMVL = 7.68 and rCL = 0.0035. The same conversion for βMVL and VL copolymerizations were unable to be achieved as in a majority of VL monomers reacted before βMVL reached equilibrium conversion, making end-capping with VL less likely. The effect is illustrated through a map of copolymer chain structure determined by the stochastic model simulation in FIGS.27-28. As shown in FIGS.5 and 29, the thermal stability of the copolymers was assessed by thermogravimetric analysis (TGA), demonstrating the stabilizing effect of higher Tc comonomers. For both copolymers, a monotonic increase in the thermal degradation temperature (Td,5%), defined here as the 5% mass loss temperature, is observed with increasing incorporation of the higher Tccomonomer. The effect is particularly notable for PβMVL-co-PCL, in which end-capping CL units kinetically limit depolymerization from chain ends. FIGS.6A and 6B show differential scanning calorimetry (DSC) data for copolymers and homopolymers. FIG.6A shows DSC data for PβMVL-co-PCL. FIG.6B shows DSC data for PβMVL-co-PVL. Samples were heated to 80 °C then cooled to –80 °C and heated again to 80 °C (10 °C min-1). Data was collected from the second heat cycle from Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 –80 to 80 °C. Endothermic heat flow upwards and plots are shifted for clarity. Glass transitions are indicated with a black triangle and melting peaks are indicated with a black square. Differential scanning calorimetry (DSC) (FIGS.6A and 6B) demonstrated that the inclusion of comonomers had minimal impact on the glass transition temperature (Tgvalues were between –64.1 °C and –52.2 °C) due at least in part to the corresponding homopolymers PβMVL, PCL, and PVL exhibit similar Tgvalues. In the PβMVL-co-PVL samples, crystallinity was observed at high VL incorporation (>75 mol%), whereas copolymers with a majority of CL exhibited some crystallinity. The appearance of relatively small melting endotherms in PβMVL-PCL copolymer samples with lower, but still majority, PCL content were accompanied by cold crystallization exotherms, which are due at least in part to the slower crystallization rate of the shorter CL-rich units formed in the gradient copolymers at intermediate CL loadings. At the highest loading of PCL (27 mol% PβMVL), a multimodal melting transition was apparent, but no cold crystallization exotherm was obtained. Multiple melting peaks are hypothesized to arise from the formation of crystallites with different thicknesses due to a heterogeneous comonomer distribution, as expected in gradient copolymers. The phenomenon may have been absent in PβMVL-co-PVL due at least in part to the lower overall degree of crystallinity or the more closely matched reactivity ratios, demonstrating a more even distribution of VL throughout the copolymer. Relative to their respective homopolymers, the copolymers demonstrate the potential for accessing a tunable degree of crystallinity and melting point with minimal impact on Tg. Endblocking experiments to stabilize βMVL polyols. As with the copolymerizations, other ways to improve the kinetic stability of PβMVL were investigated. Removal of monomer via distillation or other purification methods allows the generation of a kinetically stable polymer, but as demonstrated, the polymer can still slowly depolymerize due at least in part to a remaining active hydroxyl chain end that can undergo backbiting to give βMVL. One way of trapping polymer chains is through end capping. In some examples, the copolymer includes end caps of the one or more additional lactones. The copolymer can include end caps of a lactone comonomer with slower ROTEP kinetics. Stabilized end- capped polyesters can be used as stimuli-responsive materials for triggered degradation. Trapping polymer chains can be achieved by end-capping with a higher Tccomonomer, as described above in the case for PβMVL-co-PCL copolymers. In some examples, trapping polymer chains can include reacting the polyol with a monomer with a Tcthat exceeds the Tcof βMVL, thereby end capping the polyol with the monomer. The monomer can include a lactone with a higher Tcthan βMVL. In some cases, monomer is a monofunctional isocyanate Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 (e.g., cyclohexyl isocyanate), which end caps the polyol. In certain cases, the monomer is a difunctional isocyanate, which end caps the polyol before chain extension to yield a polyurethane. Stabilization is possible with small molecules that react with the OH chain end. An example is when polyols derived from low Tcmonomers are incorporated into polyurethanes which end caps the OH chain ends and pins the OH chain ends between hard segments. FIG.7 is a reaction schematic showing synthesis of carbamate end-blocked PβMVL from telechelic PβMVL and cyclohexyl isocyanate. FIG.7 shows the reaction of a 2 kg / mol PβMVL polyol with cyclohexyl isocyanate leads to formation of a carbamate end- capped polyester. The reaction was monitored by1H NMR and IR spectroscopy and was carried out to completion (FIGS.29 and 30). FIG.8 shows1H NMR spectra of successful endblocking by conversion of terminal methine protons at 3.7 ppm to 4.25 ppm and no significant increase of βMVL integrations at 1.10 ppm after 40 days. The long-term stability of the end-capped polymer was demonstrated by no change in the equilibrium monomer concentration over 40 days at room temperature (FIG.8) in a capped glass vial. The method demonstrates the effectiveness of end-capping to kinetically trap the polymer chain end. Sequestration with diamines. Diamidodiols, prepared through the reaction of a variety of lactone-based monomers (e.g., βMVL and CL) with diamines, show properties as chain-extenders in polyurethane syntheses. The in situ sequestration of βMVL with a variety of diamines (e.g., ethylenediamine (EtDA), hexamethylenediamine (HMDA), or 2,2'- (ethylenedioxy)bis(ethylamine) (Jeffamine EDR-148)) is shown in FIG.9. When PβMVL containing 10 wt% βMVL was reacted with these diamines, a decrease in the βMVL methyl resonances at 1 ppm and increase in the diamidodiol methine group resonances at 3.7 ppm were observed by1H NMR spectroscopy. The resonances overlap with the terminal methine groups of the polymer (FIG.31). In the cases of EtDA and HMDA, the diamidodiol was not soluble in the polymer and precipitated out of solution. This insolubility was not the case with Jeffamine EDR-148, which when reacted with βMVL gives a homogeneous liquid. While this reaction sequesters the remaining monomer, it does not end-cap and kinetically trap the βMVL polymer chain end. After 33 days, the monomer content in the PβMVL diamidodiol mixture increased from 0.5 to 5.3% (FIG.32). Despite the reduced long-term stability, sequestration can be a viable first step to manage residual βMVL in a multistep preparation of PβMVL polyols for TPUU syntheses. TPUU synthesis and characterization. Thermoplastic polyurethane-ureas with PβMVL soft segments were prepared using water or βMVL-based diamidodiol chain extenders. The TPUUs exhibit tensile properties due at least in part to hard segment content Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 and can be chemically recycled with Sn(Oct)2 to obtain βMVL. A series of PβMVL-based polyols with molar masses ranging from 2–3 kg / mol were prepared with 1,4-butanediol as an initiator and HCl as the catalyst and purified utilizing previously described methods to remove excess βMVL remaining at the end of the polymerization (Table S5). Polyol C was prepared by copolymerizing βMVL with 50% CL feed ratio. Polyol S was a homopolymer of PβMVL purified via sequestration of βMVL with Jeffamine EDR-148 to prepare a diamidodiol. Polyol D was prepared by purifying a PβMVL homopolymer via distillation. Polyols C, S, and D exhibited glass transition temperatures ranging from -70 to -60 °C and the thermal stabilities of polyol C, polyol S, and polyol D ranged from 200-270 °C with the most stable being polyol C (FIGS.33–34). Table S5. Polyol Data MnbMncdSamplea(kg / mol (kg / mol ĐcTgTd1, 5%wt% BMVL e remaining PβMVL-co-PCL (C) 268 3.1 PβMVL (S) 1.9 2.6 1.6 -60 192, 254 10 (before sequestration) PβMVL (D) 2.2 2.7 1.6 -59 152, 206 1.4 PβMVL (R) 2.3 3.0 1.4 -60 134, 197 1.5aThe sample name is composed of the polyol type and, in parenthesis, how it was prepared and purified. (S) means the remaining monomer was sequestered with Jeffamine EDR 148, (D) means the polyol was purified via distillation to remove residual monomer, and (R) refers to a polyol made with 50% virgin and 50% recycled monomer from a previously synthesized TPUU.bMolar mass obtained by end-group analysis using1H NMR spectroscopy.cRelative molar mass and dispersity were determined by SEC (HFIP, PS standards), seen in FIG. S24.dfrom TGA at a ramp rate of 10 °C min-1.eDetermined by DSC, taken on the second heating ramp at a rate of 10 °C min-1. TPUU synthesis and characterization. FIG.10 shows a reaction schematic of a synthesis of TPUUs with various polyols. FIG.10A shows polyol C (PβMVL-co-PCL P). FIG.10B shows polyol S (PβMVL with diamidodiol prepared in situ from sequestering 10 wt% remaining βMVL with Jeffamine EDR 148. FIG.10C shows polyol D (PβMVL purified via distillation). Isophorone diisocyanate (IPDI) was used as the main component of the hard segments. Utilizing polyols C, S, and D, a series of TPUUs from PβMVL and IPDI were prepared using a one-pot, solvent-free synthesis employing an overhead mechanical stirrer to Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 ensure thorough mixing during the reaction as shown in FIG.10. Organobases (e.g., 1,4- diazabicyclo[2.2.2]octane (DABCO) and 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU)) show activity for the reaction of polyols and isocyanates and have been used to make PU networks with IPDI, though full conversion can take a >6 h reaction time. While organotin catalysts (e.g., tin octoate and dibutyltin dilaurate) show higher selectivity and shorter reaction times for urethane formation, the lower boiling organobase DBU was used due at least in part to DBU could be devolatilized under reduced pressure to negate the need for nonsolvent precipitations. In the synthesis described herein, each polyol was reacted with 2 mol% DBU and excess IPDI (4:1 NCO: polyol OH for the preparation of TPUU-D and TPUU-C, 3:1 NCO: polyol OH for TPUU-S to achieve equal target hard segment contents) for 1 h to prepare isocyanate-capped PβMVL. In the case of polyol S, the diamidodiol is also end- capped in this step. The end-capped polymer and remaining diisocyanate were reacted with excess H2O to consume a fraction of the diisocyanate and form the segmented TPUU structure. Reaction progression was indicated by bubbling due at least in part to CO2evolved from the decomposition of an isocyanate into an amine upon reaction with H2O. FTIR spectroscopy was used to monitor the disappearance of the NCO stretching peak at 2270 cm-1to confirm reaction completion (FIGS.35-38). The TPUUs were purified under reduced pressure at 100 °C to devolatilize the DBU catalyst, yielding high molar mass polymers (Mn > 100 kg / mol by SEC relative to PMMA standards) in all cases (Table 1). Table 1. TPUU properties using PβMVL soft segments SampleaHS Mn polyolcMncĐcTgTdσbεb(%)fEy(MPa)f%b(kg / mol) (kg / mol) (°C)d(°C)e(MPa)fTPUU-C 24 2.9 120 1.9 –52 310 50 ± 6 830 ± 80 7.8 ± 0.5 TPUU-S 28 1.9 160 2.3 –41 276 16 ± 1 960 ± 40 22 ± 8 TPUU-D 30 2.2 150 2.2 –43 304 54 ± 3 740 ± 80 13 ± 1 TPUU-R 30 2.3 70 2.2 –44 280 54 ± 7 720 ± 40 11 ± 0.5aThe sample name contains a letter indicating the synthesis and purification method of the polyol where TPUU-C is a copolyol with 50 mol% PCL, TPUU-S is in situ sequestration of the remaining βMVL with Jeffamine EDR 148 to prepare a diamidodiol, TPUU-D is PβMVL purified via distillation and TPUU-R is a TPUU made from 50% virgin βMVL and 50% of the recovered βMVL from TPUU-D.bThe hard segment content: %HS=100*(mass of Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 IPDI) / (mass of IPDI+PβMVL). In the case of the sequestered polyol, the diamidodiol is counted as part of the hard-segment.cRelative molar mass and dispersity were determined by SEC (HFIP, PMMA standards), seen in FIG. S26.dDetermined by DSC, taken on the second heating ramp at a rate of 10 °C min-1.eObtained from TGA at a 10 °C min-1.fUltimate tensile strength (σb) and maximum elongation (εb) are the stress and elongation at break. Elastic modulus (Ey) was taken from the 0-1% strain regime and σb, and εb, were determined using uniaxial extension tests at a constant velocity of 50 mm min-1. Thermogravimetric analysis of the TPUUs (FIG.40) demonstrated higher thermal degradation temperatures than of the corresponding polyol precursors. Among the three TPUUs prepared from virgin feedstocks, TPUU-C exhibited the greatest thermal stability, due at least in part to the increased conversion of βMVL with a more thermally stable comonomer, CL. The thermal reversion of PβMVL is prevented once the hydroxyl groups are capped as carbamates in the TPUUs until thermally stimulated reversion above 180 °C. At elevated temperatures, polyesters containing β-hydrogens can be pyrolyzed to generate olefins and carboxylic acid groups that can accelerate the rate of depolymerization. The TPUUs exhibited glass transition temperatures corresponding to the soft segments from -52 to -44 °C as seen by differential scanning calorimetry, consistent with restricted movement of the soft segments by hard segments (Table 1 and FIG.41). No melting transitions were observed in any of the TPUUs due at least in part to the non- symmetric IPDI isocyanate suppressing crystallinity and leading to increased elasticity and clarity when incorporated as hard-segments in TPUs. IPDI was used as the hard segment component in non-crystalline TPUUs using polycarbonate diols as the soft-segments which exhibit elastic properties. The tensile properties of the TPUUs by uniaxial extension tests are shown in FIG. 11. Tensile samples were extended at a rate of 50 mm min-1until break. TPUU-C and TPUU- D exhibited stresses at break greater than 50 MPa and strains at break above 600%. TPUU-S did not show as high tensile strength, with stresses at break around 15 MPa. The reduced tensile strength of TPUU-S could be due at least in part to the presence of diamidodiol segments in the PUU, which chemically resemble the soft segments more than the asymmetric IPDI-based hard segments. The diamidodiol segments could be acting as a plasticizer due at least in part to low molar mass and flexibility, which could dilute entanglements in the soft segments rather than toughening the hard segments through hydrogen bonding and limiting the tensile strength of these materials. The Young’s modulus Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 of the TPUUs ranged from 7–22 MPa with the highest modulus coming from TPUU-S. TPUU-S did not exhibit high tensile strengths, the high Young’s modulus may be due at least in part to hydrogen bonding between segments, which is not disrupted at low strains. Dynamic mechanical thermal analysis (DMTA) of TPUU-C and TPUU-D showed a plateau modulus over a range of temperatures, with a flow temperature near 200 °C that could be due at least in part to urethane reversion as shown in FIG.12. DMTA samples were heated from -80 °C to 200 °C at a rate of 5 °C min-1. TPUU-S displayed a higher plateau modulus, consistent with a higher Young’s modulus from tensile testing, but a lower flow temperature (70 °C). Decreased flow temperatures are seen in TPU elastomers from βMVL and diamidodiol chain extenders, which have been attributed to hard and soft segment phase mixing. A lower flow temperature can be due at least in part to a reduction in soft segment entanglements due at least in part to diamidodiol segment dilution (which accounts for 5 wt% of total TPUU). Using a smaller chain diamine for sequestration could suppress this effect and lead to tougher TPUUs with higher flow temperatures. TPUU samples were extended to 50% strain at a rate of 50 mm min-1for 20 cycles to characterize material recovery, as shown in FIG.13. TPUU-C demonstrated recovery with 20% energy loss calculated from the area under the unloading curve after the first loading cycle. Energy losses relative to the first cycle remained constant at around 10% (Table S6). TPUU-S exhibited the highest energy loss for the first cycle when compared to the other TPUUs, which could be due at least in part to the presence of the long diamidodiol chain extender possibly diluting entanglements. High energy losses for the first cycle of hysteresis were observed in TPUs from βMVL and hexamethylene diamine chain extenders. The decrease in hysteresis values also correlates to an increase in molar mass of the soft segment. Longer soft segments lead to more complete microphase separation, and less susceptibility to deformation, as shown in TPUs from poly-δ-decalactone and TPUUs from poly(propylene oxide). Table S6. Hysteresis energy loss for different TPUUs over 20 cycles Cycle Sample 1 2 10 20 TPUU-C 19% 11% 10% 10% TPUU-S 70% 57% 53% 31% TPUU-D 36% 23% 20% 19% TPUU-R 36% 24% 22% 22% Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 Due at least in part to PβMVL’s low ceiling temperature, chemical recycling of TPUU-D to obtain βMVL was performed by heating TPUU-D to 210 °C with 0.5 wt% Sn(Oct)2 for 3 hours. The recovered βMVL was obtained in >90% yield in 1 h, after which conversion plateaued. The monomer showed purity with the only contaminant being 1,4- butanediol (BDO), the initiator used for polymerization in the original polyol. While GC-MS helped quantify the purity of βMVL, BDO was not visible (FIG.42). The amount of BDO was quantified by1H NMR spectroscopy and found to be 1.8 wt% of the total mixture (FIG. 43) compared to the starting TPUU which contained 3.4 wt% BDO. The BDO was not recovered likely due at least in part to incomplete conversion of the ring closing depolymerization, leaving some PβMVL and BDO in the residue. Using a 50% feedstock of recycled βMVL and 50% from virgin βMVL, PβMVL was prepared according to the procedure in reaction schematic shown in FIG.1 to obtain a recycled polyol (polyol R) that showed a similar molar mass of 2.3 kg / mol relative to the original polyol D which had a molar mass of 2.2 kg / mol (Table S5). Polyol R was reacted with IPDI, and chain extended with water according to the procedure in the reaction schematic shown in FIG.14 to obtain a recycled TPUU (TPUU-R) of molar mass 74 kg / mol (FIG. S31). TPUU-R exhibited similar tensile properties to the original material, TPUU-D, shown in FIG.7. The recoverable tensile properties of the TPUU-R demonstrate the viability of chemical recycling as an option when elastomers cannot be reprocessed into similar value materials due at least in part to loss of mechanical integrity or presence of other impurities from recycling streams. TPUU-R showed a similar plateau modulus when compared to TPUU-D. TPUU-R started to soften around 180 °C, a slightly lower temperature than TPUU-D, likely due at least in part to a lower molar mass. The hysteresis properties of TPUU-R in FIG.13 showed similar energy loss profiles over 20 cycles when compared to TPUU-D due at least in part to their similar chemical composition. The kinetics of homo and copolymerization of βMVL with CL and VL using HCl in ether to prepare low molar mass polyols was described herein. The lactone monomers show rapid kinetics with an HCl catalyst, achieving >80% conversion in less than 90 min for loadings as little as 0.1 mol%. At these catalyst loadings, HCl can be removed from the reaction vessel under reduced pressure. Chemical modifications to mitigate challenges associated with the equilibrium concentration of βMVL were presented. βMVL can be distilled from the polyol at moderate temperatures without significant depolymerization, copolymerized with high Tcmonomers to prepare more thermodynamically stable Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 copolymers, sequestered with diamines to prepare diamidodiols in situ, or any combination thereof. The three synthetic and purification methods were used to prepare a series of polyols that were incorporated as soft segments in thermoplastic polyurethane-urea elastomers. The TPUU elastomers were prepared in a one-pot, two-step method, and purified through selective devolatilization of the catalyst. The TPUUs are thermally stable and exhibit tougher mechanical properties than similar PβMVL analogues. The use of PβMVL as the soft segment allows the TPUUs to be chemically recycled back to the starting monomer, which can be repolymerized and used to make recycled TPUUs that exhibit similar properties to the primary materials. Cross-Linking of PβMVL’s The scheme below shows a representative one-pot, solvent-free synthesis of photocrosslinkable PβMVL, with covalent acrylate-based crosslinks depicted as circles and non-covalent hydrogen bonding interactions depicted as rectangles. Table S7 below shows Molecular characteristics of photocrosslinkable PβMVL library. e MbResidual DegreeSamplance of Mx,eff (kg mol-1) Tpolym(°C) βMVL Swellingd(kg mol-1) P-10-0 10.2 7.4 ± 0.4 6.2 ± 0.2 Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 P-10-8 9.5 -4 5.2 6.4 ± 0.5 6.4 ± 0.6 P-10-23 10.2 22 10.2 5.0 ± 0.2 2.5 ± 0.1 P-11-35 10.7 45 16.0 5.1 ± 0.9 1.5 ± 0.1 P-5-14 5.4 22 7.1 4.1 ± 0.3 1.8 ± 0.1 P-28-22 28.0 22 10.2 6.5 ± 0.1 3.7 ± 0.1aSample name is composed of P-polyol molar mass (Mn,NMR in kg mol-1)-diamidodiol loading (wt%).bObtained by end-group analysis via1H NMR spectroscopy prior to crosslinking.cObtained via1H NMR spectroscopy prior to sequestration. Residual βMVL post- polymerization in sample P-10-0 was distilled off at 120 °C.dObtained by comparison of swollen volume (in CHCl3, after 3x extraction with CHCl3) to initial, dry volume post UV- crosslinking.eCalculated from the plateau modulus (GN0) at 25 °C measured by DMTA post UV-crosslinking. FIG.67 shows graphs summarizing dynamic mechanical thermal analyses (DMTA) plots of series with A) diamidodiol loading held constant and PβMVL molar mass varied from 0-35 wt%. B) PβMVL molar mass held constant and diamidodiol loading varied from 0-35 wt%. Samples were heated from -60 to 180 °C at a rate of 5 °C min-1. Storage modulus (E’) is shown in closed circles and loss modulus (E”) is shown in open circles. FIG.68 shows graphs summarizing the tensile properties of crosslinked PβMVLs. Samples were extended at a rate of 50 mm min-1. a) Representative stress-strain curves of series with diamidodiol loading held constant and PβMVL molar mass varied from Mn = 5-28 kg mol-1. b) Representative stress-stress curves of series with PβMVL molar mass held constant and diamidodiol loading varied from 0-35 wt%. Elastic 50A processed by the same method (a commercial vat photopolymerization resin) is shown for comparison. c) Hysteresis plots of two crosslinked PβMVLs (top: P-10-23, bottom: P-11-35). Samples were extended to 50% strain for 20 cycles. FIG.69 shows graphs summarizing the suitability of photocrosslinkable PBMVLs for vat photopolymerization applications. a) Steady shear viscosity of materials at 1 s-1and 25 °C before crosslinking as a function of polyol molar mass. The exact composition of Elastic 50A is not known but predicted to be small molecule and oligomeric species. b) Curing kinetics of crosslinkable resins, demonstrated through storage modulus as a function of time at room temperature (25 °C). UV light (λ = 365 nm, I = 10 mW / cm2) was turned on at Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 60 s and remained on for 10 min. c) Image of [insert here] produced by vat photopolymerization of P-11-35 resin. Additional Supporting Information Derivation of Empirical EaThe empirical rate equation for the polymerization of βMVL can be expressed as: െ^^^^^^^^^^^^ ^^௫ ௬ ௭^^^^ൌ ^^^^^ ^^^^^^^^ ^^ℎ^^^^^^ ^^^^^ ൌ k^HCl^ ^ROH^We assume [ROH] (propagating chain end = [initiator] = 0.0945 M) and [HCl] (= 0.0828 M) remain constant over the course of the reaction. As shown in FIG.70, multiple polymerization temperatures were probed while maintaining a constant catalyst loading ([HCl]0) and target Mn([ROH]). (S1) FIG. 71 shows that first order kinetic fits at different temperatures with constant [BDO]0, [βMVL]0, and [HCl]0. [M]eq was approximated based on equilibrium data after 24 h. Negligible volume of mixing was assumed. Across these conditions, the linearity in the ln([M- Meq] / [M0-Meq]) vs. time plots to approximately 50% conversion suggests the rate expression is first order in [βVML] (x = 1) as shown in FIG.71. The calculated kappfor each condition from the first order fits can be plotted as a function of inverse temperature, as shown in Fig.1. Fitting these data to the Arrhenius equation: ^^^1 ^^^^^^ ൌ െ ^ ^^^^^^-1^^ ^^ results in the calculated Ea= 14 ± 1 kJ mol . (S2) FIG.72 shows stacked1H NMR spectra (CDCl3, 500 MHz, 16 scans, 5 s relaxation delay) of PβMVL polymerization at three temperatures prior to devolatilization of HCl^Et2O, showing an increase in equilibrium monomer concentration with increased polymerization temperature. FIG.73 shows stacked1H NMR spectra (CDCl3, 500 MHz, 16 scans, D1 = 10 s) of representative synthesis of acrylated PβMVL-based material, including sequestration of residual βMVL by diamine and acrylation by 2-isocyanatoethyl acrylate. Table S7 below shows thermal and molecular characteristics of crosslinked PβMVLs. Sample Mna(kg mol-1) ĐaGel Fracb(%) Tgc(°C) P-10-0 10.8 1.5 85 ± 3 -50.4 P-10-8 12.9 1.4 90 ± 10 -49.9 P-10-23 11.7 1.4 98 ± 8 -49.0 P-11-35 13.6 1.3 91 ± 2 -48.2, 18.1 Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 P-5-14 8.3 1.4 110 ± 20 -48.2 P-28-22 31.3 1.2 77 ± 1 -51.5, 16.7 P-0-100 -- -- -11.6 aObtained by SEC equipped with RI detector using PS standards prior to crosslinking.bGel fraction = wpost extraction / winitial x 100, extracted with CHCl3.cDetermined by DSC on the second heating ramp at 10 °C min. FIG.74 shows differential scanning calorimetry (DSC) data for crosslinked PβMVLs. Samples were heated to 80 °C, cooled to -80 °C, and then heated to 80 °C at a ramp rate of 10 °C min-1. Data shown are taken from the second heat (-80 °C to 80 °C). Endothermic heat flow is upward. Plots are stacked for clarity and glass transitions are indicated with triangles. Table S9 shows the mechanical behavior of crosslinked PβMVL Table S9 σbε (%)aEyb P-10-23 6 ± 1 100 ± 20 48 ± 8 1.8% 8.2% 8.6% 6.4% P-11-35 8 ± 2 105 ± 8 60 ± 10 25% 10% 9.8% 9.3% P-5-14 2.8 ± 0.5 80 ± 10 30 ± 20 P-28-22 3.3 ± 0.4 380 ± 70 9 ± 4 Elastic 6 ± 3 130 ± 20 47 ± 3 10% 6.0% 5.6% 9.4% 50A aDetermined by uniaxial extension tests at 50 mm min-1. Ultimate tensile strength (σb) and maximum elongation (εb) are the stress and elongation at break, calculated as the average and standard deviation of at least 5 samples. Elastic modulus (Ey) was taken from the 0–10% strain regime.bHysteresis energy losses over 20 cycles, measured at 50 mm min-1. FIG.75 shows Hysteresis plots of crosslinked materials (a: P-10-0, b: P-10-8, c: Elastic 50A). Samples were extended to 50% strain for 20 cycles at a rate of 50 mm min-1. FIG. 76 shows steady-shear viscosity measurements as a function of shear rate at room temperature (25 °C). Viscosities are measured prior to crosslinking and compared to a commercial resin (Elastic 50A). FIG.77 shows curing kinetics of crosslinkable resins, shown as normalized modulus as a function of time at room temperature (25 °C). UV light (λ = 365 nm, I = 10 mW / cm2) was turned on at 60 s and remained on for 10 min. Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 FIG.78 relates to the reaction scheme shown below: are of diamidodiol segments and allophanate bonds from free isocyanate. FIG.79 shows the1H NMR spectra (CDCl3, 500 MHz, 16 scans) of virgin βMVL (bottom) and recycled βMVL (top) recovered from crosslinked PβMVL (P-10-8) via distillation. The recovered βMVL contains a small amount of 1,4-butanediol, the initiator from the previous βMVL polymerization. FIG.80 shows the1H NMR spectrum of βMVL (CDCl3, 500 MHz, 16 scans). FIG. 81 shows the1H NMR spectrum of distilled PβMVL (CDCl3, 500 MHz, 16 scans, D1 = 10 s). FIG.82 shows the1H NMR spectrum of acrylated diamidodiol (CDCl3, 500 MHz, 16 scans). FIG.831H NMR spectrum of P-10-0 (CDCl3, 500 MHz, 16 scans, D1 = 10 s). Although this disclosure contains many specific embodiment details, these should not be construed as limitations on the scope of the subject matter or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this disclosure in the context of separate embodiments can also be implemented, in combination, in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments, separately, or in any suitable sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. Particular embodiments of the subject matter have been described. Other embodiments, alterations, and permutations of the described embodiments are within the Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results. Accordingly, the previously described example embodiments do not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure.

Claims

Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 WHAT IS CLAIMED IS:

1. A method of synthesizing a polyol, the method comprising: combining β-methyl-δ-valerolactone (βMVL) and hydrochloric acid to yield a reaction mixture, wherein, before combining, a temperature of the βMVL and the hydrochloric is in a range of about 20 °C to about 50 °C; and polymerizing the βMVL in the reaction mixture by ring opening transesterification to yield the polyol and residual βMVL.

2. The method of claim 1, wherein combining the βMVL with the hydrochloric acid comprises combining the βMVL with a solution comprising diethyl ether and the hydrochloric acid.

3. The method of claim 1, wherein an initial concentration of the βMVL in the reaction mixture is in a range of about 5 M to about 10 M.

4. The method of claim 1, wherein a concentration of hydrochloric acid in the reaction mixture is in a range of about 0.001 M to about 0.01 M.

5. The method of claim 1, wherein the reaction mixture further comprises an initiator.

6. The method of claim 5, wherein the initiator comprises a difunctional initiator.

7. The method of claim 6, wherein the difunctional initiator comprises benzene dimethanol or butanediol or any other diol.

8. The method of claim 5, wherein a concentration of the initiator is in a range of about 0.1 M to about 0.5 M.

9. The method of claim 1, wherein the polyol comprises a linear hydroxy-containing polymer.

10. The method of claim 9, wherein the linear hydroxy-containing polymer is telechelic.Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 11. The method of claim 9, wherein the linear hydroxy-containing polymer is a homopolymer.

12. The method of claim 1, further comprising purifying the polyol.

13. The method of claim 12, wherein purifying the polyol comprises devolatilizing the hydrochloric acid in the reaction mixture.

14. The method of claim 12, wherein purifying the polyol comprises distilling the reaction mixture to remove the βMVL from the reaction mixture.

15. The method of claim 12, wherein purifying the polyol comprises combining a diamine with the reaction mixture, thereby sequestering the residual βMVL as a diamidodiol.

16. The method of claim 1, wherein the reaction mixture further comprises one or more additional lactones, and further comprising copolymerizing the βMVL with the one or more additional lactones to yield a copolymer.

17. The method of claim 16, wherein the one or more additional lactones comprise δ- valerolactone, ε-caprolactone, or a combination thereof.

18. The method of claim 16, wherein a total amount of the one or more additional lactones is in a range of about 25 mol% βMVL to about 75 mol% βMVL.

19. The method of claim 16, wherein the copolymer comprises end caps of the one or more additional lactones.

20. The method of claim 16, wherein the one or more additional lactones comprises ε- caprolactone, and the reaction mixture comprises an equilibrium concentration of less than 2 wt% βMVL.

21. The method of claim 1, further comprising reacting the polyol with an isocyanate, thereby end capping the polyol with the isocyanate.Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 22. The method of claim 1, further comprising reacting the polyol with a monomer with a Tcthat exceeds the Tcof βMVL, thereby end capping the polyol with the monomer.

23. The method of claim 1, further comprising reacting a diisocyanate with the polyol to yield a thermoplastic polyurethane-urea with soft segments comprising the polyol.

24. The method of claim 23, further comprising recycling the thermoplastic polyurethane- urea with an organotin or organozinc catalyst to yield βMVL.

25. The method of claim 23, wherein the diisocyanate comprises isophorone diisocyanate.

26. The method of claim 1, wherein the polymerizing occurs in an unheated reaction vessel.

27. The method of claim 1, wherein the polyol has a molar mass of less than 10 kg / mol.

28. The method of any one of claims 1-27, wherein the method further comprises contacting the polyol with a cross linking agent.

29. The method of claim 28, wherein the cross linking agent is a photo cross linking agent.

30. The method of claim 28, wherein the cross linking agent is an acrylate-based cross- linking agent.

31. The method of claim 30, wherein the acrylate-based cross-linking agent is 2- isocyanatoethyl acrylate.

32. The method of claim 28, wherein the method provides a polyol substituted with one or more cross linking agents.

33. The method of claim 28, wherein the method provides a first polyol substituted with one or more cross linking agents and a second polyol substituted with one or more cross linking agents.Attorney Docket No.: 09531-0557WO1 / UMN 2024-109 34. The method of claim 33, wherein the method comprising contacting the first and second polyols substituted with one or more cross linking agents for a time sufficient to cross link the first and second polyols substituted with one or more cross linking agents.

35. The method of claim 28, wherein the method provides a plurality of polyols substituted with one or more cross linking agents.

36. The method of claim 35, wherein the method comprises contacting the plurality of polyols substituted with one or more cross linking agents for a time sufficient to cross link the plurality of polyols substituted with one or more cross linking agents.

37. The method of any one of claims 28-36, wherein the polyol is PβMV.

38. The method of any one of claims 28-37, wherein the polyol is prepared by the methods claimed in any one of claims 1-27.

39. A PβMV substituted with one or more cross linking agents.

40. The PβMV of claim 39, wherein the cross linking agent is a photo cross linking agent.

41. The PβMV of claim 39 or 40, wherein the cross linking agent is an acrylate-based cross-linking agent.

42. The PβMV of any one of claims 39-41, wherein the acrylate-based cross-linking agent is 2-isocyanatoethyl acrylate.

43. A PβMV optionally substituted with one or more cross linking agents prepared by any of the methods described and claimed herein.

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