Highly Processable Covalently-Bonded Network Polymers and the Anhydrous Route to Blends

Abstract

The present invention generally relates to covalent network polymers prepared from imine-linked oligomers and a separate crosslinker containing a reactive moiety selected from the group consisting of epoxies, isocyanates, bismaleimides, sulfides, polyurethanes, anhydrides, polyesters, and combinations thereof. The covalent network polymers disclosed herein are advantageously made via an anhydrous reaction, allowing this class of materials to have the highest glass transition temperatures known to date. Furthermore, the disclosed covalent network polymers can be formed in continuous processes, such as additive manufacturing processes to produce three-dimensional objects, or roll-to-roll processes to produce covalent network polymer films or fully cured prepregs in various size formats. [Selection diagram] Figure 29

Description

Detailed Description of the Invention

[0001] [Cross - Reference to Related Applications]

[0001] This application claims the benefit and priority of U.S. Provisional Patent Application No. 62 / 727,785, filed on September 6, 2018, and U.S. Provisional Patent Application No. 62 / 860,837, filed on June 13, 2019, each of which is hereby incorporated by reference in its entirety.

[0002] [Description of Research Funded by the Federal Government]

[0002] This invention was made with government support under Grant No. 1632199 awarded by the National Science Foundation of the United States. The government has certain rights in this invention.

[0003] [Background]

[0003] Dynamic covalent chemistry is a branch of covalent chemistry and, due to its reversibility, has much in common with the non - covalent field of supramolecular chemistry that uses a discrete number of molecules as building blocks for creating self - organizing systems. The concept of supramolecules can be applied to the formation of dynamic covalent systems to promote, if necessary, short - chain (oligomer) polymer formation, long - chain polymer formation, or network formation. In particular, by selecting monomer concentration, monomer structure, and stoichiometric ratio, a predetermined architecture can be achieved. For example, when the monomers in solution are at a low concentration, short - chain species are generally preferentially formed, while increasing the concentration of monomers in solution leads to an increase in polymer chain length. In addition, by selecting monomers with a specific structure and number of reactive moieties, the formation of a desired connection pattern or shape becomes possible. By way of illustration, linear monomers each containing two reactive end - groups react with angled monomers each containing two complementary reactive end - groups to form squares (4 linear monomers + 4 angled (90°) monomers), pentagons (5 linear monomers + 5 angled (108°) monomers), hexagons (6 linear monomers + 6 angled (120°) monomers), etc. These concepts are well - known to polymer chemists and scientists studying molecular - level phenomena.

[0004]

[0004] This disclosure relates in particular to dynamic covalent polymers (DCPs), which include covalent bonds that are capable of reversibly forming and breaking when an environmental or chemical stimulus is applied. DCPs are desirable because they combine the robustness of covalent bonds with unique material properties including self-healing, ductility, and responsiveness to stimuli. DCPs are commonly also referred to as vitrimers, ductile thermosets, and covalent adaptable polymer networks.

[0005]

[0005] However, when the environmental stimulus applied to some types of DCPs is water, strong non-covalent interactions result in DCP materials that tend to have a decreased glass transition temperature and become plasticized. This phenomenon is particularly problematic when using a condensation reaction to form DCPs because water is a byproduct of the reaction and it is difficult to remove water without creating air bubbles or voids trapped within the polymer structure.

[0006] [Summary]

[0006] The present invention generally relates to covalent network polymers capable of undergoing the formation / destruction of dynamic bonds that promote self-healing and ductility. The covalent network polymers disclosed herein are advantageously made by an anhydrous reaction that does not utilize water or produce water as a byproduct. The absence of water in this way results in a higher glass transition temperature for the covalent network polymer than known DCPs, and the disclosed covalent network polymer will have the highest glass transition temperature known to date for this class of materials.

[0007]

[0007] Furthermore, the disclosed covalent network polymers can be formed in a continuous process, such as a stereolithography process for manufacturing three-dimensional objects, or a roll-to-roll process for manufacturing covalent network polymer films or fully cured prepregs in various size formats.

[0008]

[0008] In one aspect, the covalent network polymer is prepared from an imine-bonded oligomer and an independent crosslinking agent containing a reactive moiety selected from the group consisting of epoxy, isocyanate, bismaleimide, sulfide, polyurethane, anhydride, polyester, and combinations thereof.

[0009]

[0009] In one embodiment, the imine-bonded oligomer contains one or more primary and / or secondary and / or tertiary amines, and the molar ratio of the amine to the crosslinking agent is between 0.01:1 and 100:1, or between 0.05:1 and 100:1, or between 0.1:1 and 100:1, or between 0.25:1 and 50:1, or between 0.5:1 and 25:1, or between 1.25:1 and 10:1, or between 1.5:1 and 5:1, or between 1.75:1 and 2.5:1, or a molar ratio of 2:1.

[0010]

[0010] In one embodiment, the imine-bonded oligomer contains between 2 and 1000 repeating units, or between 2 and 500 repeating units, or between 2 and 250 repeating units, or between 2 and 100 repeating units, or between 3 and 80 repeating units, or between 4 and 60 repeating units, or between 5 and 50 repeating units, or between 5 and 30 repeating units.

[0011]

[0011] In one embodiment, the imine-bonded oligomer has a weight average molecular weight between 200 and 100,000 daltons, or between 300 and 75,000 daltons, or between 400 and 50,000 daltons, or between 500 and 35,000 daltons, or between 750 and 20,000 daltons, or between 1,000 and 10,000 daltons.

[0012]

[0012] In one embodiment, the reaction of the imine-bonded oligomer and the crosslinking agent to create the covalent network polymer is anhydrous. For example, in one embodiment, the formation of the imine-bonded oligomer may not be anhydrous, but once the imine-bonded oligomer is isolated, it can be combined with the crosslinking agent in an anhydrous reaction, such as a curing step.

[0013]

[0013] In one embodiment, the imine-linked oligomer is linear or branched.

[0014]

[0014] In one embodiment, the imine-linked oligomer contains at least one secondary amine within the oligomer backbone.

[0015]

[0015] In one embodiment, the imine-linked oligomer is prepared from a monofunctional or polyfunctional amine and a monofunctional or polyfunctional aldehyde or carbonyl. For example, the polyfunctional aldehyde or carbonyl may be selected from the group consisting of terephthalaldehyde, 2,5-diformylfuran, diformylthiophene, diformylpyrrole, diformylimidazole, and combinations thereof. In one embodiment, the polyfunctional carbonyl may be selected from the group consisting of aldehydes, ketones, carboxylic acid esters, amides, enones, anhydrides, imides, and combinations thereof. In one embodiment, the polyfunctional aldehyde or carbonyl may be derived from a renewable biological source.

[0016]

[0016] In one embodiment, the crosslinking agent is a molecule selected from the group consisting of novolak resins, bisphenols (e.g., bisphenol A (BPA)), monoglycidyl, diglycidyl, or triglycidyl molecules, N-containing triglycidyl molecules, cresols containing epoxy or SU-8 photoresist, isocyanates, bismaleimides, sulfides, polyurethanes, anhydrides, and / or polyester functional groups.

[0017]

[0017] In one embodiment, the covalent network polymer disclosed herein is a vitrimer and / or a thermosetting polymer. In one embodiment, the covalent network polymer is capable of undergoing a dynamic bond exchange reaction even in the cured state. In one embodiment, the covalent network polymer does not cure irreversibly.

[0018] In one embodiment, the covalent network polymer disclosed herein is characterized by a glass transition temperature of at least 100°C, or at least 95°C, or at least 90°C. In one embodiment, the covalent network polymer disclosed herein has a glass transition temperature in the range between 0°C and 300°C, or between 30°C and 300°C, or between 50°C and 300°C, or between 100°C and 300°C, or between 200°C and 300°C, or between 250°C and 300°C, or between 265°C and 300°C, or between 275°C and 300°C.

[0019]

[0019] In one aspect, the composite comprises a covalent network polymer prepared from an imine-bonded oligomer and an independent crosslinking agent comprising a reactive moiety selected from the group consisting of epoxy, isocyanate, bismaleimide, sulfide, polyurethane, anhydride, polyester, and combinations thereof, and another material. In one embodiment, the composite is reworkable or non-reworkable. In one embodiment, the composite is impact resistant and / or water resistant. In one embodiment, the composite is characterized by a glass transition temperature of at least 100°C, or at least 95°C, or at least 90°C, or at least 85°C, or at least 80°C, or at least 75°C, or at least 70°C, or at least 65°C, or at least 60°C. In one embodiment, the composite has a glass transition temperature in the range between 50°C and 300°C, or between 60°C and 250°C, or between 100°C and 300°C, or between 200°C and 300°C, or between 250°C and 300°C, or between 265°C and 300°C, or between 275°C and 300°C.

[0020]

[0020] In one aspect, the covalent network polymer blend is a mixture of a covalent network polymer and another compound, such as, but not limited to, hydrogel, polyvinyl chloride (PVC), polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), etc.

[0021]

[0021] In one aspect, a component of a transport means or a constituent of an electronic device includes the composite disclosed herein.

[0022]

[0022] In one aspect, a collision energy management (CEM) structure includes the composite disclosed herein. In one embodiment, the CEM structure includes low strain fibers, high strain fibers, or a combination of low strain fibers and high strain fibers.

[0023]

[0023] In one aspect, a method of forming a covalently bonded network polymer includes combining an imine-bonded oligomer with a crosslinking agent having a reactive moiety selected from the group consisting of epoxy, isocyanate, bismaleimide, sulfide, polyurethane, anhydride, polyester, and combinations thereof.

[0024]

[0024] In one embodiment, the combining step is performed by mechanical stirring, reactive extrusion, reactive injection molding, slot die coating, and / or shear mixing.

[0025]

[0025] In one embodiment, a method of forming a covalently bonded network polymer includes using a resin to (i) impregnate a woven, non-woven, unidirectional, cut, or chopped fibrous material, (ii) form a film, or (iii) form a three-dimensional object.

[0026]

[0026] In one embodiment, the fibrous material is impregnated by extrusion followed by compression, pultrusion, slot die coating, solvent dip impregnation, and / or hot melt impregnation.

[0027]

[0027] In one embodiment, the film is a free-standing film, the film is supported on a release liner, or the film is a layer in a multi-layer device. In one embodiment, the film is formed by extrusion, slot die coating, gravure coating, Mayer rod coating, slide coating, polishing rod coating, and / or lithography.

[0028]

[0028] In one embodiment, the three-dimensional object is formed by injection molding, additive manufacturing, laser cutting, and / or CNC machining.

[0029]

[0029] In one embodiment, a method of forming a covalent network polymer includes the step of curing the covalent network polymer. In one embodiment, the curing step includes heating, UV treatment, IR treatment, microwave treatment, and / or addition of a catalyst, accelerator, or radical initiator.

[0030]

[0030] In one embodiment, the composite disclosed herein may be joined to another component by applying local heat at the point of contact between the composite and the other component to create welding by dynamic covalent interactions; applying local ultrasonic energy at the point of contact between the composite and the other component; and / or applying local pressure at the point of contact between the composite and the other component. In one embodiment, the other component is metal, a thermoplastic resin, a ceramic, a glass, a covalent network polymer, or a combination thereof.

[0031]

[0031] In one embodiment, the step of applying local heat includes utilizing convection, radiation, conduction, and / or induction. For example, the energy may be applied in the form of convection, radiation (e.g., laser, IR, microwave), conduction (e.g., heat press / molding), and / or induction (e.g., via conductive fibers or conductive additives).

[0032]

[0032] In one embodiment, a method of joining components includes applying a structural adhesive comprising a covalent network polymer disclosed herein between the components. In one embodiment, the components are metal, a thermoplastic resin, a ceramic, a glass, a covalent network polymer, or a combination thereof. In one embodiment, both components are non-vitrimer components, both components are vitrimer-containing components, or a combination of a non-vitrimer and a vitrimer-containing component.

[0033]

[0033] In one aspect, a method of recycling a composite comprising a covalent network polymer disclosed herein comprises contacting the composite with an acid, an additional amount of an imine-bonded oligomer, or an additional amount of a crosslinking agent to depolymerize the covalent network polymer into a liquid; and physically separating the liquid from other materials in the composite.

[0034]

[0034] Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Brief Description of the Drawings

[0035]

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[0036] [Detailed Description]

[0063] Generally, the terms and phrases used in this specification have meanings recognized in the art, which can be found by referring to standard literature, journal articles, and contexts known to those skilled in the art. The following definitions are provided to clarify their specific usage in the context of this specification.

[0037]

[0064] As used herein, an "imine-linked oligomer" is an oligomer containing at least one non-terminal imine moiety such that the imine moiety is within the oligomer backbone.

[0038]

[0065] As used herein, a "moiety" is a part of a molecule.

[0039]

[0066] As used herein, "polyfunctional" is used to describe a molecule containing at least two specified moieties. For example, a polyfunctional amine contains at least two amine moieties, and a polyfunctional aldehyde or carbonyl contains at least two aldehyde or carbonyl moieties, respectively. In addition to the specified moieties, a polyfunctional molecule may contain additional different moieties in some embodiments.

[0040]

[0067] As used herein, a "crosslinking agent" is a molecule that chemically reacts with and covalently bonds to an oligomer and / or polymer.

[0041]

[0068] As used herein, "composite" includes a plurality of parts or substances joined in a heterogeneous configuration. The composites disclosed herein include a covalent network polymer and at least one other material. For example, the covalent network polymer may be layered with the other material, used to impregnate and / or encapsulate the other material, encapsulated by the other material, or otherwise mixed with the other material in other ways.

[0042]

[0069] "Proximal" and "distal" refer to the relative positions of two or more objects, planes, or surfaces. For example, an object that is closer to a reference point relative to the position of another object in space is considered to be proximal to the reference point, while an object that is farther away from the reference point relative to the position of another object in space is considered to be distal to the reference point.

[0043]

[0070] The terms "direct and indirect" describe the action or physical position of one object relative to another object. For example, an object that acts on or contacts another object "directly" does so without the intervention of an intermediary. In contrast, an object that acts on or contacts another object "indirectly" does so through an intermediary (e.g., a third component).

[0044]

[0071] Figures 1, 2, and 3 illustrate the results of dynamic mechanical analysis (DMA) experiments to determine the glass transition temperature (Tg) of composites fabricated using imine-linked oligomers and epoxy-functionalized novolak crosslinkers according to multiple embodiments. Figure 1 shows the DMA of dipropylene triamine + terephthaldehyde imine-linked oligomer cured with novolak-poly[(phenyl glycidyl ether)-co-formaldehyde] epoxy crosslinker. Figure 2 shows the DMA of dipropylene triamine + ethylenediamine + terephthaldehyde imine-linked oligomer cured with novolak-poly[(phenyl glycidyl ether)-co-formaldehyde] epoxy crosslinker. Figure 3 shows the DMA of 4,4'-oxydianiline + terephthaldehyde imine-linked oligomer cured with novolak-poly[(phenyl glycidyl ether)-co-formaldehyde] epoxy crosslinker.

[0045]

[0072] Figure 4 illustrates the results of a DMA experiment to determine the Tg of a composite fabricated using a diethylene triamine + terephthaldehyde imine-linked oligomer and an epoxy-functionalized bisphenol A (BPA) crosslinker.

[0046]

[0073] Figure 5 illustrates the results of a DMA experiment to determine the Tg of a composite fabricated using a diethylene triamine + terephthaldehyde imine-linked oligomer and a nitrogen-containing triglycidyl epoxy crosslinker (N,N-diglycidyl-4-glycidyloxyaniline).

[0047]

[0074] Figure 6 illustrates the results of a DMA experiment to determine the Tg of a composite fabricated using a diethylene triamine + terephthaldehyde imine-linked oligomer and a high molecular weight (over 1 kDa) cresol epoxy crosslinker (poly[(o-cresyl glycidyl ether)-co-formaldehyde], M n 1080).

[0048]

[0075] Figure 7 shows the results of a DMA experiment to determine the Tg of a composite fabricated using a diethylenetriamine + terephthalaldehyde imine bond oligomer and a low molecular weight (less than 1 kDa) cresol epoxy crosslinking agent (poly[(o-cresyl glycidyl ether)-co-formaldehyde], M n 345).

[0049]

[0076] Figure 8 shows the results of a DMA experiment to determine the Tg of a composite fabricated using a diethylenetriamine + terephthalaldehyde imine bond oligomer and a triglycidyl epoxy crosslinking agent (trimethylolpropane triglycidyl ether).

[0050]

[0077] Figure 9 shows the results of a DMA experiment to determine the Tg of a composite fabricated using a diethylenetriamine + terephthalaldehyde imine bond oligomer and SU-8 photoresist.

[0051]

[0078] Figure 10 shows the non-limiting scope of amines and carbonyl precursors that can be used in the preparation of imine bond oligomers.

[0052]

[0079] Figure 11 shows a short beam shear experiment to determine the shear strength of an 8-layer pre-cured composite composed of a diethylene + terephthalaldehyde imine bond oligomer and a novolac-poly[(phenyl glycidyl ether)-co-formaldehyde] epoxy crosslinking agent, combined with a 9 ounce / square yard glass twill fabric by solvent dip impregnation and then cured in a hot press, layer by layer.

[0053]

[0080] Figure 12 shows the thermogravimetric analysis plot of a composite fabricated using a diethylenetriamine + terephthalaldehyde imine bond oligomer and an epoxy-functionalized cresol (poly[(o-cresyl glycidyl ether)-co-formaldehyde], M n 1080).

[0054]

[0081] Figure 13 illustrates the isothermal (at 100 °C) viscometer data of the uncured neat resin fabricated using an imine-linked oligomer and an epoxy-functionalized crosslinker (novolak-poly[(phenyl glycidyl ether)-co-formaldehyde]). This shows the viscosity, pot life, and out life that enable the processability of hot melt resin injection, reactive extrusion, reactive injection molding, lithography, and other processes.

[0055]

[0082] Figure 14 shows devices of composites (prepared from an imine-linked oligomer crosslinked with a novolak-poly[(phenyl glycidyl ether)-co-formaldehyde] epoxy crosslinker and 9 ounce / square yard twill woven glass fiber) that underwent a drop impact test after being shaped. The upper row shows competing impact-absorbing materials. The lower row shows multilayer glass fiber composites solidified and reshaped from a flat shape to a curved shape based on pre-cured sheet stock. The devices in the lower row were prepared using a resin fabricated with an imine-linked oligomer and an epoxy-containing crosslinker. From the left column to the right column, material samples weighing 10 pounds 5 ounces after drops of 18 inches, 24 inches, and 72 inches are shown respectively. The impact energies of these drops correspond to the impacts of baseballs at approximately 39 mph, 44 mph, and 77 mph respectively. The figure shows that the upper row has catastrophic damage and the lower row has surface damage.

[0056]

[0083] Figure 15 shows top and bottom photographs of two re - formable imine - bonded epoxy - crosslinked multilayer covalent network polymer - carbon fiber composite devices laminated in different fiber directions. Both devices are composed of the same layer of a woven carbon fiber composite that was solidified and reformed from a flat shape to a curved shape based on a pre - cured sheet stock. One device was laminated such that one weaving direction was aligned with the formed curvature and the other weaving direction was perpendicular to the formed curvature. The other device was laminated such that one weaving direction was at a + 45° angle to the formed curvature and the other weaving direction was at a - 45° angle to the formed curvature. Devices with fiber orientations of 0° and + 90° were observed to have delamination and severe wrinkles on the bottom side after the molding step. Devices with fiber orientations of + 45° and - 45° were observed to have minimal wrinkles on the bottom side after the molding step, but no delamination was observed.

[0057]

[0084] Figure 16 shows isothermal (at 100 °C) viscometer data for an uncured pure resin made using an imine - bonded oligomer and a sulfide - functionalized crosslinking agent. This shows the viscosity and pot life that enable processability for hot - melt resin injection, reactive extrusion, reactive injection molding, lithography, and other processes.

[0058]

[0085] Figure 17 shows dynamic mechanical analysis of a cured resin made using an imine - bonded oligomer and an isocyanate - functionalized crosslinking agent over a certain temperature range.

[0059]

[0086] Figure 18 shows isothermal (at 100 °C) viscometer data for an uncured pure resin made using an imine - bonded oligomer and a bismaleimide - functionalized crosslinking agent. This shows the viscosity and pot life that enable processability for hot - melt resin injection, reactive extrusion, reactive injection molding, lithography, and other processes.

[0060]

[0087] Figures 19 and 20 illustrate the dynamic mechanical analysis of a cured resin fabricated using an imine-bonded oligomer and a bismaleimide-functionalized crosslinker over a certain temperature range.

[0061]

[0088] Figure 21 illustrates the dynamic mechanical analysis of a cured resin fabricated using an imine-bonded oligomer and a crosslinker. The imine-bonded oligomer was prepared by combining a bio-derived 2,5-diformylfuran and a diamine precursor.

[0062]

[0089] Figure 22 illustrates the loss modulus determined by the dynamic mechanical analysis of a cured resin fabricated using an imine-bonded oligomer and a crosslinker. The imine-bonded oligomer was prepared by combining a bio-derived 2,5-diformylfuran and a diamine precursor.

[0063]

[0090] Figure 23 reports the short beam shear strength of a multilayer composite device prepared by compression molding at 270 psi at the indicated temperature and time. The individual layers included carbon fibers and a fully cured resin made using an imine-bonded oligomer and an epoxy-functionalized crosslinker. The difference in performance between devices pressed for 30 seconds and those pressed for 2400 seconds was less than 10%.

[0064]

[0091] Figure 24 is a photograph showing the reprocessing / reuse of a multilayer cured carbon fiber composite device fabricated using a resin made from an imine-bonded oligomer and an epoxy-functionalized curing agent. The yellow fluid in the vial is an oligomerized resin reacted with an excess amount of diamine monomer at room temperature in solution for 24 hours. The woven fibers in the solution contain little of the cured resin that originally surrounded them.

[0065]

[0092] Figure 25 is a photograph showing the bare woven fibers from Figure 24 removed from the solution. Only a small amount of residual resin remains, which can be easily removed by rinsing with ethanol and gentle scraping.

[0066]

[0093] Figure 26 is a photograph showing a moderately crosslinked imine-epoxy network containing 5 wt% epoxy crosslinker extruded at 180 °C into a 3 mm diameter filament. The extrusion of the imine-bonded resin was carried out through a desktop extruder. This demonstrates the processability of the non-crosslinked and minimally crosslinked imine-bonded resin in the molten state.

[0067]

[0094] Figure 27 is a photograph showing a thin film of a hot melt resin formulation (2 kg) prepared by combining an imine-bonded oligomer (1.6 kg) and an epoxy resin (0.4 kg) crosslinker. The resin was heated to 80 °C and poured into the nip between a meter roller and an applicator roller of a typical reverse roll coating, and a thin film was formed in a roll-to-roll process using silicone-coated paper as the substrate. This demonstrates that the imine-bonded oligomer can be processed into a thin film prior to curing in combination with the crosslinker. This is an important step in the efficient manufacture of composite laminates, as well as many other materials and devices.

[0068]

[0095] Figure 28 is a photograph showing the production of a towpreg material by applying a molten resin (prepared by combining an imine-bonded oligomer (1.6 kg) and an epoxy resin (0.4 kg) crosslinker) to a 6K carbon fiber tow, followed by passing through a die, cooling, and winding. Figure 28 is a photograph of the carbon fiber tow being pulled through a die after being coated with the molten resin. This demonstrates the flexibility of the imine-bonded oligomer + crosslinker that can be adapted to various processing conditions and manufacturing processes. The towpreg produced as shown in this photograph is used in the fabrication of composite pressure vessels, tape laminates, and many other products. Towpregs are also used in continuous fiber additive manufacturing.

[0069]

[0096] Figure 29 is a photograph of a 2 cm × 2 cm × 0.3 cm component 3D printed using a filament extrusion 3D printer from an imine-epoxy filament manufactured by extrusion as shown in Figure 26. This demonstrates the processability and reprocessability (extrusion of previously extruded filaments) of the imine-bonded material. Additionally, the reprocessability of the imine-bonded material by bond exchange opens up the possibility of covalent bonds across the interface between lithographic layers.

[0070] (Manufacturing and joining methods)

[0097] Composite structures and composite components can be manufactured in various ways. For example, a composite structure can be manufactured by thermocompression molding a pre-cured composite sheet stock (see Example 3).

[0071]

[0098] Furthermore, composite components can be joined to other composite or non-composite components. In one embodiment, the method of joining composite components includes applying local energy (including, but not limited to, heat, convection, IR, laser, microwave, electromagnetic induction, sonic energy) and pressure at the contact points between the components to generate welding by vitrimer interaction. In one embodiment, the method of joining composite components includes applying local ultrasonic energy and pressure at the contact points between the components to generate welding by vitrimer interaction. In one embodiment, the method of joining a vitrimer-containing component to a thermoplastic resin-containing component includes applying local ultrasonic energy at the contact point between the components to generate welding. In one embodiment, the method of joining a vitrimer-containing component to a metal component includes using an adhesive for vitrimer-containing structures. In one embodiment, the method of joining non-vitrimer components, such as metals, thermoplastic resins, composites, ceramics, and glasses, includes using an adhesive for vitrimer-containing structures.

[0072] (Electronic devices)

[0099] Traditionally, materials used to support and encapsulate metals and semiconductors are typically epoxy matrix materials that form irreversibly, making the reuse of electronic devices particularly difficult. However, the covalent network polymers disclosed herein can be used in electronic devices to facilitate reuse. For example, the covalent network polymers (vitrimers) disclosed herein can be used in electronic devices as follows: Circuit boards containing fibers, fillers, and / or additives Circuit boards that can be reprocessed by heat, pressure, or ultrasonic treatment Circuit boards that become multilayer circuits when reprocessed Circuit boards that curve when reprocessed Potting materials Adhesives for electronic applications Microchip substrates or encapsulation materials Electrical insulation coatings for electronic applications Thermal insulation coatings Thermally conductive coatings

[0073]

[0100] Replacing these epoxy materials with the covalent network polymers disclosed herein, electronic devices can be easily reused, for example, by adding one more kind of precursor to oligomerize and liquefy the resin to dissolve the covalent network polymer, and recovering solid metal and semiconductor components, for example, by filtration. The resin solution can be used to manufacture more resins with the same mechanical properties. For example, a method for reusing electronic components containing the covalent network polymers disclosed herein may include treating with a solution containing a stoichiometric excess of a vitrimer precursor (e.g., a primary amine) to oligomerize and soften or solubilize the vitrimer resin. Then, following depolymerization, physical separation of other components and materials including components and sub-components containing metals, thermoplastics, thermosets, composites, ceramics, glass, fibers, fillers, additives, etc. is performed. Further chemical treatment of the depolymerized vitrimer solution can isolate vitrimer oligomers, monomers, additives, fillers, surfactants, etc.

[0074]

[0101] Another method of recycling electronic components including the covalently bonded network polymers disclosed herein involves physically separating the heterogeneous components and materials after treating with an acid solution to depolymerize the vitrimer resin, and optionally further chemically treating the depolymerized vitrimer solution.

[0075]

[0102] The method of recycling the previously disclosed electronic components is also applicable to non - electronic parts including a mixture of covalently bonded network polymers and heterogeneous materials. For example, the covalently bonded network polymers (vitrimers) disclosed herein can be used in structural parts, such as primary or secondary structures of transportation means for marine vessels, automobiles, aerospace, shipping or other mobile applications. These structural parts may be recycled by addition of an acid or excess precursor and physical separation as described above.

[0076] (Collision energy management materials)

[0103] A composite structure in which the matrix material includes a covalently bonded network polymer enables covalent bond exchange at high temperatures, thereby allowing the composite structure to be used for collision energy management (CEM). The composite CEM structure is designed to optimize specific sustained crushing forces during a collision event. For example, the composite CEM structure can be designed to be an optimal CEM for low - speed collisions (0 - 10 mph), medium - speed collisions (11 - 35 mph), high - speed collisions (36 mph and above), and / or racing applications (100 mph and above). Exemplary composite CEM structures include bumpers, pillars, side impact protection components, rear impact protection components, and any other structural components of a collision energy management system.

[0077]

[0104] The composite structure is designed for CEM such that at a certain strain rate (impact velocity), low-strain fibers (e.g., carbon fibers) exhibit brittle fracture while the resin restricts brittle fracture and extends the sustained crushing force, and at other strain rates, the resin matrix exhibits brittle fracture while high-strain fibers (e.g., glass fibers, UHMWPE fibers, hemp or other natural fibers, metal fibers such as steel or aluminum, or other synthetic fibers such as aramid fibers) act to restrict brittle fracture and extend the sustained crushing force. The composite CEM structure can contain low-strain fibers, high-strain fibers, or both low-strain and high-strain fibers.

[0078]

[0105] The compositions and methods disclosed herein are further illustrated by the following examples. These examples are for illustrative purposes only and are not intended to limit the invention.

[0079] [Example 1]

[0106] This example shows the synthesis of an exemplary covalent network polymer.

[0080]

[0107] (a) An imine-bonded oligomer was formed by condensation of a diamine and a dicarbonyl precursor followed by removal of water by annealing at high temperature.

[0081]

[0108] (b) The imine-bonded oligomer prepared by mixing at room temperature as described above was combined with a crosslinking agent capable of forming a covalent network polymer when combined with the imine-bonded oligomer. At least one of the following processes for combining the crosslinking agent and the imine-bonded oligomer was used: reactive extrusion, reactive injection molding, shear mixing, Mayer rod coating, blade coating, slot die coating, and / or lithography.

[0082]

[0109] (c) The covalent network polymer formed in (b) was cured by heating, UV treatment, IR treatment, microwave treatment, and / or addition of a catalyst, accelerator, or radical initiator.

[0083]

[0110] The non-limiting case of Example 1 is shown below in the preparation of the following amine-terminated imine-bonded oligomer (1) and the subsequent reaction with the indicated epoxy crosslinking agent. [Chemical formula]

[0084]

[0111] Oligomer synthesis procedure:

[0112] To a dry 500 mL Erlenmeyer flask was added terephthaldehyde (94.7 g, 0.706 mol), and then 200 mL of an EtOH solvent was added. The mixture was stirred for 5 minutes until most of the terephthaldehyde had dissolved. Separately, diethylenetriamine (10.2 g, 0.099 mol), 4,4'-methylenebis(cyclohexylamine) (93.6 g, 0.445 mol), and 1,6-diamino-2,2,4(2,4,4)-trimethylhexane (70.4 g, 0.445 mol) were combined and stirred by hand until thoroughly mixed. The amine mixture was added dropwise over 10 minutes, and the temperature of the solution was monitored with a thermocouple. The temperature of the solution reached 60 °C during the addition. Subsequently, the reaction vessel was allowed to cool to room temperature, the solution was treated with activated molecular sieves (100 g), followed by decantation, and the sieves were rinsed with ethanol. The decanted solution was combined with the rinse liquid, and the solvent was evaporated on a rotary evaporator, leaving a yellow-orange elastomeric solid (240 g). [Chemical formula]

[0085]

[0113] Cured epoxy imine network synthesis procedure:

[0114] The imine-bonded oligomer obtained above (240 g) was heated to 60 °C with stirring to form a viscous melt. To this was added a 60 °C melt of the epoxy resin Epon 828 (106 g). The reaction mixture was stirred thoroughly and then poured into a silicone mold and oven-cured at 150 °C for 3 hours. A hard, glossy orange solid with a Tg (Tanδ) of 143 °C and a moisture absorption (2-hour boil according to ASTM D6980) of 1.5% was obtained.

[0086] [Example 2]

[0115] The reactive mixture from (b) of Example 1 was processed as follows: i. The reactive mixture is impregnated into woven, non-woven, unidirectional, cut or shredded fibrous materials by extrusion followed by compression, drawing, slot die coating, solvent dip impregnation, ball mill grinding and / or hot melt impregnation. ii. A film (either free-standing, supported by a release liner, or as a component of a multilayer device) is formed by extrusion, slot die coating, gravure coating, Mayer rod coating, slide coating, polishing rod coating, and / or lithography techniques. iii. A three-dimensional shape is formed by injection molding and / or 3D printing.

[0087]

[0116] After or during (i), (ii) or (iii), the covalent network polymer was cured by heating, UV treatment, IR treatment, microwave treatment and / or addition of a catalyst or accelerator.

[0088]

[0117] Non-limiting case of Example 2-a:

[0118] A hot melt resin formulation (2 kg) (prepared by combining an imine bond oligomer (1.6 kg) and an epoxy resin (0.4 kg) crosslinker) was heated to 80 °C and poured into the nip between a metering roller and an applicator roller in a typical reverse roll coating, and a thin film was formed in a roll-to-roll process using silicone coated paper as the substrate. Subsequently, this thin film was combined with a carbon fiber fabric (12k twill weave) and passed through two heated (80 °C) compression rollers to form a pre-impregnated carbon fiber laminate. Subsequently, the laminate was cured and then incorporated into a multilayer device by heat compression forming (150 °C, 5 minutes, 500 psi). The multilayer composite device was found to have an interlaminar shear strength of 76 MPa (ASTM D2344).

[0089]

[0119] Non-limiting case of Example 2-b:

[0120] The imine-bonded oligomer was extruded at 140 °C into a filament with a diameter of 1.75 mm. The filament was loaded into a filament extruder 3D printer. Using the 3D printer, a part with dimensions of 2 cm × 2 cm × 0.3 cm was printed.

[0090]

[0121] Non-limiting case of Example 2-c:

[0122] The imine-bonded oligomer was co-extruded with ABS plastic at 180 °C into a filament with a diameter of 1.75 mm. The filament was loaded into a filament extruder 3D printer. Using the 3D printer, a part with dimensions of 2 cm × 2 cm × 0.3 cm was printed.

[0091]

[0123] Non-limiting case of Example 2-d:

[0124] A moderately cross-linked imine-epoxy network containing 5 wt% epoxy cross-linking agent was extruded at 180 °C into a filament with a diameter of 1.75 mm. The filament was loaded into a filament extruder 3D printer. Using the 3D printer, a part with dimensions of 2 cm × 2 cm × 0.3 cm was printed.

[0092] [Example 3]

[0125] This example shows a method of compression molding a covalent network polymer and carbon fibers to form a composite solid object and evaluating the properties of the composite.

[0093]

[0126] In some embodiments, a multilayer composite structure comprising a dynamic covalent network polymer and reinforcing fibers may not be actually reshaped. As shown in FIG. 15, a fully pre-cured unidirectional carbon fiber composite layer was produced by impregnating carbon fibers with a resin formed from an imine-bonded oligomer and an epoxy-functionalized crosslinking agent and then curing. These layers containing about 40% resin and 60% fibers by weight were aligned such that all the unidirectional fibers were parallel, and multiple layers were bonded by compression molding at 150° C. (50° C. higher than the glass transition temperature of the material). The resulting material was aligned such that the fiber direction was parallel to the bending direction and cut into dimensions suitable for ASTM D648-16 Method B, "Deflection Temperature of Plastics Under Edgewise Bending Load." The result of the deflection test was a heat deflection temperature of the material exceeding 300° C. Perhaps due to the interlaminar shear force, when the fiber direction coincides with the direction of the force within the multilayer device, the composite is actually still not moldable even several hundred degrees Celsius above the glass transition temperature of the resin.

[0094]

[0127] As shown in FIG. 23, when a fully cured covalent network polymer formed by the reaction of an imine-bonded oligomer and an epoxy-functionalized crosslinking agent was compression molded at 270 psi at the indicated temperature and time with carbon fibers, a difference of less than 10% in short beam shear strength distinguishes the performance of the device pressed for 30 seconds from that of the device pressed for 2400 seconds. Such a significant reduction in manufacturing time leads to a considerable reduction in manufacturing cost.

[0095] [Description of Incorporation by Reference and Variant Forms]

[0128] All documents cited throughout this application, including patent documents such as issued or registered patents or equivalents; published patent applications; and non-patent documents or other source materials are hereby incorporated by reference in their entirety as if each cited document were individually incorporated by reference to the extent that each cited document does not conflict with the disclosure herein at least in part (e.g., a partially conflicting cited document is incorporated by reference except for the partially conflicting portion of the cited document).

[0096]

[0129] The terms and expressions employed in this specification are not terms of limitation but of description, and in using such terms and expressions there is no intention of excluding any equivalents of the features shown and described or portions thereof, it being recognized that various modifications are possible within the scope of the invention as set forth in the claims. Accordingly, although the invention has been specifically disclosed by way of preferred embodiments, exemplary embodiments and any features, it is possible for those skilled in the art to make changes and modifications to the concepts disclosed herein, and such changes and modifications are considered to be within the scope of the invention as defined by the appended claims. The specific embodiments given herein are examples of useful embodiments of the invention, and it will be apparent to those skilled in the art that the invention can be practiced using numerous variations of the devices, device components, and method steps described herein. As will be apparent to those skilled in the art, the methods and devices useful in this method and device can include numerous optional compositions as well as processing elements and steps. All technically known functional equivalents of materials and methods are intended to be included in this disclosure. Nothing in this specification should be construed as an admission that the invention has no right to antedate such disclosure by virtue of prior invention.

[0097]

[0130] When a group of substituents is disclosed herein, each of the individual elements of that group and all sub-groups are understood to be disclosed separately. When Markush groups or other groupings are used herein, all individual elements of the group, as well as all possible combinations and sub-combinations of the group, are intended to be individually included in this disclosure.

[0098]

[0131] It should be noted that, as used in this specification and the appended claims, the singular forms "a", "an", and "the" include references to the plural unless the context clearly dictates otherwise. Thus, for example, reference to "a molecule" includes references to a plurality of such molecules and their equivalents known to those skilled in the art. Similarly, the terms "a" (or "an"), "one or more", and "at least one" can be used interchangeably herein. It should also be noted that the terms "comprising", "including", and "having" can be used interchangeably. The expression "as claimed in any of claims XX to YY" (where XX and YY refer to claim numbers) is intended to provide a plurality of dependent claims in alternative forms and, in some embodiments, is interchangeable with the expression "as claimed in any one of claims XX to YY".

[0099]

[0132] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described.

[0100]

[0133] When ranges are given herein, for example, ranges of integers, temperature ranges, time ranges, composition ranges, or concentration ranges, it is always intended that all intermediate ranges and subranges, as well as all individual values included in the given range, are included in the disclosure. As used herein, a range specifically includes the values provided as the endpoints of the range. As used herein, a range specifically includes all integer values of the range. For example, the range of 1 to 100 specifically includes the endpoints 1 and 100. It is understood that any subrange or individual value within the ranges or subranges described in this specification can be excluded from the claims of this specification.

[0101]

[0134] As used herein, "comprising" is synonymous with "including", "containing", or "characterized by" and can be used interchangeably, is inclusive or open-ended, and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of" excludes any element, step, or raw material not specified in the claim elements. As used herein, "consisting essentially of" does not exclude materials or steps that do not substantially affect the basic and novel characteristics of the patent claim. In each example herein, the terms "comprising", "consisting essentially of", and "consisting of" can all be replaced with either of the other two terms. The invention exemplified herein can be preferably implemented in the absence of one or more elements or one or more constraints not specifically disclosed herein. (Appendix 1) A covalently crosslinked network polymer prepared from an imine-bonded oligomer and an independent crosslinking agent containing a reactive moiety selected from the group consisting of epoxies, isocyanates, bismaleimides, sulfides, polyurethanes, anhydrides, polyesters, and combinations thereof. (Appendix 2) The covalently crosslinked network polymer according to Appendix 1, wherein the imine-bonded oligomer contains one or more primary and / or secondary and / or tertiary amines, and the amine and the crosslinking agent are present in a molar ratio between 0.01:1 and 100:1. (Appendix 3) The covalently crosslinked network polymer according to Appendix 1 or 2, wherein the reaction between the imine-bonded oligomer and the crosslinking agent is anhydrous. (Appendix 4) The covalently crosslinked network polymer according to Appendix 1 or 2, wherein the imine-bonded oligomer contains a secondary amine within the oligomer backbone. (Appendix 5) The covalently crosslinked network polymer according to Appendix 1 or 2, wherein the imine-bonded oligomer is prepared from a monofunctional or polyfunctional amine and a monofunctional or polyfunctional carbonyl. (Appendix 6) The covalently crosslinked network polymer or resin according to Appendix 5, wherein the polyfunctional carbonyl is selected from the group consisting of terephthalaldehyde, 2,5-diformylfuran, diformylthiophene, diformylpyrrole, diformylimidazole, and combinations thereof. (Appendix 7) The covalently crosslinked network polymer according to Appendix 1 or 2, wherein the crosslinking agent is a molecule selected from the group consisting of novolac resins, bisphenols, monoglycidyl, diglycidyl or triglycidyl molecules, N-containing triglycidyl molecules, cresol or SU-8 photoresist functionalized with epoxy, isocyanates, bismaleimides, sulfides, polyurethanes, anhydrides, and / or polyesters. (Appendix 8) The covalently crosslinked network polymer according to Appendix 1 or 2, which is a vitrimer and a thermosetting polymer. (Appendix 9) The covalently crosslinked network polymer according to Appendix 1 or 2, characterized by a glass transition temperature of at least 60°C. (Appendix 10) A covalently bonded network polymer according to appended claim 1 or 2, characterized by a glass transition temperature in the range from 0 °C to 300 °C. (Appended claim 11) A composite comprising a covalently bonded network polymer according to any one of appended claims 1 to 10 and another material. (Appended claim 12) The composite according to appended claim 11, which is reshaped or non-reshaped. (Appended claim 13) The composite according to appended claim 11, characterized by a glass transition temperature of at least 100 °C. (Appended claim 14) The composite according to appended claim 11, characterized by a glass transition temperature in the range from 50 °C to 300 °C. (Appended claim 15) A component of a means of transport or a component of an electronic device, comprising the composite according to appended claim 11. (Appended claim 16) The composite according to appended claim 11, which is impact-resistant and / or water-resistant. (Appended claim 17) A collision energy management (CEM) structure, comprising the composite according to appended claim 11. (Appended claim 18) The CEM structure according to appended claim 17, comprising low-strain fibers, high-strain fibers, or a combination of low-strain fibers and high-strain fibers. (Appended claim 19) A method for forming a covalently bonded network polymer, comprising the step of combining an imine-bonded oligomer with an independent crosslinking agent having a reactive moiety selected from the group consisting of epoxy, isocyanate, bismaleimide, sulfide, polyurethane, anhydride, polyester, and combinations thereof. (Appended claim 20) The method according to appended claim 19, wherein the imine-bonded oligomer comprises one or more primary and / or secondary and / or tertiary amines, and the amine and the crosslinking agent are present in a molar ratio between 0.01:1 and 100:1. (Appended claim 21) The method according to appended claim 19 or 20, wherein the combining step is carried out by mechanical stirring, reactive extrusion, reactive injection molding, slot die coating, and / or shear mixing. (Appended claim 22) Using the covalently bonded network polymer to (i) impregnate a woven, non-woven, unidirectional, cut, or chopped fibrous material, (ii) form a film, or (iii) form a three-dimensional object The method according to any one of appended claims 19 to 21, further comprising the step. (Appended claim 23) The method according to appended claim 22, wherein the fibrous material is impregnated by extrusion followed by compression, pultrusion, slot die coating, solvent dip impregnation, and / or hot melt impregnation. (Appended claim 24) The method according to Supplementary Note 22, wherein the film is a self - standing film, the film is supported by a release liner, or the film is a layer in a multilayer device. (Supplementary Note 25) The method according to Supplementary Note 22, wherein the film is formed by extrusion, slot - die coating, gravure, Mayer rod, slide, polishing rod, and / or lithography. (Supplementary Note 26) The method according to Supplementary Note 22, wherein the three - dimensional object is formed by injection molding, additive manufacturing, laser cutting, and / or CNC machining. (Supplementary Note 27) The method according to Supplementary Note 22, further comprising the step of curing the covalent - bond network polymer. (Supplementary Note 28) The method according to Supplementary Note 27, wherein the curing step includes heating, UV treatment, IR treatment, microwave treatment, and / or addition of a catalyst, accelerator, or radical initiator. (Supplementary Note 29) A method of joining the composite according to Supplementary Note 11 to another component, comprising the step of applying local heat to a contact point between the composite and the other component to generate welding by dynamic covalent - bond interactions, the step of applying local ultrasonic energy to a contact point between the composite and the other component, and / or the step of applying local pressure to a contact point between the composite and the other component The method comprising the above steps. (Supplementary Note 30) The method according to Supplementary Note 29, wherein the step of applying local heat includes utilizing convection, radiation, conduction, and / or induction. (Supplementary Note 31) The method according to Supplementary Note 29, wherein the other component is metal, thermoplastic resin, ceramic, glass, covalent - bond network polymer, or a combination thereof. (Supplementary Note 32) A method of joining components together, comprising the step of applying a structural adhesive containing the covalent - bond network polymer according to Supplementary Note 1 between the components. (Supplementary Note 33) The method according to Supplementary Note 32, wherein the components are metal, thermoplastic resin, ceramic, glass, covalent - bond network polymer, or a combination thereof. (Supplementary Note 34) A method of recycling a composite containing the covalent - bond network polymer according to Supplementary Note 1, comprising the step of contacting the composite with an acid, an additional amount of imine - bond oligomer, or an additional amount of the cross - linker to depolymerize the covalent - bond network polymer into a liquid, and the step of physically separating the liquid from other materials The method comprising the above steps.

Claims

1. Prepared from an anhydrous mixture of an imine-bonded oligomer and an independent crosslinking agent containing a reactive moiety selected from the group consisting of epoxy, isocyanate, sulfide, urethane, acid anhydride, ester, and combinations thereof, A covalent network polymer that is a solution-reusable vitrimer and a thermosetting polymer.

2. The covalent network polymer according to claim 1, wherein the imine-bonded oligomer contains one or more primary or secondary or tertiary amines, and the amine and the crosslinking agent are present in a molar ratio between 0.01:1 and 100:

1.

3. The covalent network polymer according to claim 1 or 2, wherein the imine-bonded oligomer contains a secondary amine within the oligomer backbone.

4. The covalent network polymer according to claim 1 or 2, wherein the imine-bonded oligomer is prepared from a monofunctional or polyfunctional amine and a monofunctional or polyfunctional carbonyl.

5. The covalent network polymer according to claim 4, wherein the polyfunctional carbonyl is selected from the group consisting of terephthalaldehyde, 2,5-diformylfuran, diformylthiophene, diformylpyrrole, diformylimidazole, and combinations thereof.

6. The covalent network polymer according to claim 1 or 2, wherein the crosslinking agent is a molecule selected from the group consisting of monoglycidyl molecules, diglycidyl molecules, triglycidyl molecules, N-containing triglycidyl molecules, and cresol containing epoxy.

7. The covalent network polymer according to claim 1 or 2, characterized by a glass transition temperature of at least 60 °C determined by peak tan delta obtained by dynamic mechanical analysis (DMA).

8. A composite comprising the covalent network polymer according to any one of claims 1 to 7 and another material.

9. The composite according to claim 8, characterized by a glass transition temperature of at least 100 °C determined by peak tan delta obtained by dynamic mechanical analysis (DMA).

10. A method of forming a covalent network polymer, which is a solution-reusable vitrimer and a thermosetting polymer, comprising the step of combining an imine-bonded oligomer with an independent crosslinking agent having a reactive moiety selected from the group consisting of epoxy, isocyanate, sulfide, urethane, acid anhydride, ester, and combinations thereof, A method wherein the reaction between the imine-bonded oligomer and the crosslinking agent is anhydrous.

11. The method according to claim 10, wherein the imine-bonded oligomer contains one or more primary or secondary or tertiary amines, and the amine and the crosslinking agent are present in a molar ratio between 0.01:1 and 100:

1.

12. The method according to claim 10 or 11, wherein the combining step is carried out by mechanical stirring, reactive extrusion, reactive injection molding, slot die coating, or shear mixing.

13. Using the covalent network polymer to (i) impregnate woven, non-woven, unidirectional, cut or shredded fibrous materials, (ii) form a film, or (iii) form a three-dimensional object The method according to any one of claims 10 to 12, further comprising the step of.

14. The method according to claim 13, wherein the fibrous material is impregnated by extrusion followed by compression, pultrusion, slot die coating, solvent dip impregnation, or hot melt impregnation.

15. The method according to claim 13, wherein the film is a free-standing film, the film is supported by a release liner, or the film is a layer in a multilayer device.

16. The method according to claim 13, wherein the film is formed by extrusion, slot die coating, gravure, Mayer rod, slide, polishing rod, or lithography.

17. The method according to claim 13, wherein the three-dimensional object is formed by injection molding, additive manufacturing, laser cutting, or CNC machining.

18. The method according to claim 13, further comprising the step of curing the covalent network polymer.

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