Low temperature self-healing fully bio-based elastomer

Abstract

The application discloses a low-temperature self-healing full-biological-based elastomer and belongs to the technical field of materials. The full-biological-based elastomer is synthesized by using a carboxyl-terminated low-molecular-weight biological-based unsaturated aliphatic prepolymer which is synthesized by polycondensation of nontoxic and renewable biological resources dihydric alcohol and diacid and then is crosslinked by an epoxy structure. The elastomer prepared by the application contains a physical crosslinking double dynamic network formed by beta hydroxy ester groups dynamic covalence and H bonds, which endows the full-biological-based elastomer with the functions of self-healing at low temperature and reprocessing of the material. The full-biological-based elastomer is prepared by using full-biological-based monomers, does not depend on fossil resources, and has simple preparation process, and can be used in multiple fields such as flexible wearable sensors and organic solar power generation.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a low-temperature self-healing fully bio-based elastomer. Background Technology

[0002] While facing enormous challenges in energy, resources, and the environment, the chemical industry, with its massive energy and resource consumption, faces severe problems. With rapid economic development, the rate of crude oil consumption is accelerating, existing crude oil reserves are dwindling, and the shortage and depletion of petrochemical resources are inevitable. Utilizing renewable resources and reducing dependence on non-renewable fossil fuels is of great significance. Bio-based elastomers are polymers synthesized from bio-based monomers. Currently, with the maturity of bio-fermentation technology, bio-based monomers are being produced and commercialized on a large scale, leading to the development of various bio-based monomers, such as succinic acid, itaconic acid, and glycerol. In 2016, Academician Zhang Liqun's team at Beijing University of Chemical Technology synthesized polyester elastomers (BEE) through melt polycondensation reactions using bio-based monomers such as sebacic acid and itaconic acid, laying the foundation for the engineering application of bio-based polyester elastomers.

[0003] However, compared to thermoplastic polymers, thermosetting polymers, due to their permanent cross-linking, restrict the fluidity of polymer chains. Thus, once fully cured, thermosetting polymers cannot be reshaped, reprocessed, or recycled. Therefore, thermosetting polymers are major contributors to environmental pollution and bear significant responsibility for resource waste. Introducing dynamic covalent bonds (β-hydroxy ester groups, disulfide bonds, etc.) or dynamic non-covalent bonds (H bonds, metal coordination bonds, etc.) into the polymer network to prepare dynamically cross-linked polymers is an effective method to endow traditional cross-linked polymers with reversible properties. Dynamically cross-linked polymers can alter their topological structure through dynamic covalent bond exchange reactions induced by external stimuli while maintaining the mechanical properties of traditional cross-linked polymers. This not only brings extensibility and recyclability to cross-linked polymers but also endows traditional polymers with many excellent properties such as self-healing and shape memory, which has significant scientific implications for promoting the development of bio-based elastomers.

[0004] CN101450985A discloses a polyester-type bioengineering rubber and its preparation method. Using aliphatic diols, saturated aliphatic diacids, and unsaturated diacids derived from renewable resources as raw materials, unsaturated aliphatic polyesters are synthesized through direct polycondensation, followed by chemical crosslinking with an oxide DCP to obtain a polyester-type bioengineering rubber with a permanently crosslinked network. Although the raw materials are bio-based monomers, the permanently crosslinked structure prevents it from being remodeled, reprocessed, or recycled. CN115160535A discloses a vegetable oil-based self-healing elastomer and its preparation method, where H bonds and disulfide bonds are introduced into the elastomer's dynamic network to impart self-healing properties. However, most reported self-healing crosslinked elastomers currently exhibit self-healing properties above room temperature, while research on achieving self-healing at low temperatures is limited. Summary of the Invention

[0005] The purpose of this invention is to provide a fully bio-based crosslinked elastomer and its preparation method, which uses renewable biomass monomers as raw materials to obtain a fully bio-based elastomer with ultra-toughness, low-temperature self-healing properties, and reprocessability.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] This invention discloses a low-temperature self-healing bio-based crosslinked elastomer membrane material, obtained by ring-opening polymerization of a carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer and epoxidized soybean oil. Its topological structure contains a multiple dynamic network composed of H bonds and β-hydroxy ester bonds. The preparation method is as follows:

[0008] (1) Synthesis of carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymers

[0009] A bio-based dicarboxylic acid, a diol, and a polymerization inhibitor with a total acid-to-alcohol molar ratio of 1.05–2 are added to a reactor. The reaction temperature is 130–190 °C, and the reaction time is 2–8 h to obtain a carboxyl-terminated bio-based aliphatic prepolymer.

[0010] (2) Chemical crosslinking

[0011] The carboxyl-terminated bio-based aliphatic prepolymer from step (1) is melt-blended with epoxidized soybean oil and transesterification catalyst at 100–120°C for 1–2 h, and then cured at 120–160°C for 6–12 h to obtain a low-temperature self-healing bio-based elastomer.

[0012] In one embodiment of the present invention, in step (1), the bio-based dicarboxylic acid is at least one of itaconic acid, sebacic acid, succinic acid, and dimeric fatty acid (DAA).

[0013] In one embodiment of the present invention, in step (1), the bio-based diol is at least one of 1,4-butanediol, 1,3-propylene glycol, rubber seed oil-based diol, palm oil-based diol, and sunflower seed oil-based diol.

[0014] In one embodiment of the present invention, in step (1), the molar ratio of dicarboxylic acid to diol is (1-2):1; further optionally, it is 1.25:1.

[0015] In one embodiment of the present invention, in step (1), the polymerization inhibitor is either 4-methoxyphenol or hydroquinone.

[0016] In one embodiment of the present invention, in step (1), the amount of polymerization inhibitor added relative to the total mass of the diacid and diol is 0.05-0.5 wt%.

[0017] In one embodiment of the present invention, in step (1), the number average molecular weight of the carboxyl-terminated low molecular weight bio-based aliphatic prepolymer is 1500-4800.

[0018] In one embodiment of the present invention, in step (1), the reaction temperature is preferably 150-180°C.

[0019] In one embodiment of the present invention, in step (2), the transesterification catalyst is any one of zinc acetate and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD).

[0020] In one embodiment of the present invention, in step (2), the amount of transesterification catalyst used is 5-20 mol% of the carboxyl content.

[0021] In one embodiment of the present invention, in step (2), the molar ratio of the epoxy groups in the epoxidized soybean oil to the carboxyl groups in the carboxyl-terminated bio-based aliphatic prepolymer is (1.0-2.2):1. Preferably (1.0-1.4):1; more preferably 1.2:1.

[0022] The present invention also provides the application of the above-mentioned low-temperature self-healing bio-based cross-linked elastomer membrane material in flexible wearable sensors.

[0023] The present invention also provides the application of the above-mentioned low-temperature self-healing bio-based cross-linked elastomer membrane material in the field of organic solar power generation.

[0024] The present invention also provides the application of the above-mentioned low-temperature self-healing bio-based cross-linked elastomer film material in the preparation of liquid crystal products.

[0025] The present invention also provides the application of the above-mentioned low-temperature self-healing bio-based cross-linked elastomer membrane material in the preparation of biomedical materials.

[0026] The present invention also provides the application of the above-mentioned low-temperature self-healing bio-based cross-linked elastomer membrane material in electronic devices or equipment.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The fully bio-based elastomer prepared in this invention uses renewable resources as raw materials. This strategic approach, based on topological design, to synthesize elastomers via a non-petroleum route, is beneficial in alleviating the challenge of petroleum resource depletion. This invention uses bio-based diacids and diols to obtain a carboxyl-terminated low-molecular-weight bio-based prepolymer through simple melt polycondensation, which is then crosslinked with epoxidized soybean oil to obtain the fully bio-based elastomer. The crosslinked network contains β-hydroxy ester dynamic covalent bonds and a double crosslinked network formed by H bonds. Through topological design, the elongation at break of the fully bio-based elastomer can reach up to 1200%, and it can be reprocessed multiple times under the catalysis of TBD. Furthermore, due to the large number of H bonds and a glass transition temperature of -30°C, the fully bio-based elastomer possesses rapid self-healing ability at low temperatures; specifically, scratches disappear within 12 hours at -5°C, demonstrating high self-healing efficiency. It has great application potential in flexible wearable devices and solar power generation.

[0029] Compared with existing self-healing polyurethane elastomers, the fully bio-based crosslinked elastomers of this invention have higher drug resistance and thermal stability due to their crosslinked structure, thus having a wider range of applications. Attached Figure Description

[0030] Figure 1 This invention describes the preparation process of an ultra-tough, low-temperature self-healing, reprocessed, and fully bio-based elastomer.

[0031] Figure 2 This is a scratch self-healing diagram of the all-bio-based elastomer in Example 6.

[0032] Figure 3 This is a diagram showing the reprocessing of the all-bio-based elastomer in Example 6.

[0033] Figure 4 The stress-strain curves are those of the fully bio-based elastomer in Example 6 after reprocessing. Detailed Implementation

[0034] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.05 wt% 4-methoxyphenol were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. Nitrogen gas flow rate was set to 0.15 L / min, magnetic stirring speed was set to 380 r / min, reaction temperature was 130 °C, and reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 1520, the weight-average molecular weight was 1535, and the polydispersity index was 1.01, determined by gel permeation chromatography (GPC, THF phase).

[0037] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 5 wt% TBD to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.2. Under a nitrogen atmosphere, at a temperature of 100 °C, stir and mix for 30 min, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120 °C (3 h), 140 °C (5 h), and 160 °C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -29.8 °C.

[0038] Example 2

[0039] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.2 wt% 4-methoxyphenol were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. The nitrogen flow rate was set to 0.15 L / min, the magnetic stirring speed was set to 380 r / min, the reaction temperature was 140 °C, and the reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 1860, the weight-average molecular weight was 1915, and the polydispersity index was 1.03, determined by gel permeation chromatography (GPC, THF phase).

[0040] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 10 wt% TBD to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.2. Under a nitrogen atmosphere, at a temperature of 100°C, stir and mix for 30 minutes, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120°C (3 h), 140°C (5 h), and 160°C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -29.9°C.

[0041] Example 3

[0042] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.5 wt% 4-methoxyphenol were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. Nitrogen gas flow rate was set to 0.15 L / min, magnetic stirring speed was set to 380 r / min, reaction temperature was 150 °C, and reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 2210, the weight-average molecular weight was 2276, and the polydispersity index was 1.03, determined by gel permeation chromatography (GPC, THF phase).

[0043] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 20 wt% TBD to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.2. Under a nitrogen atmosphere, at a temperature of 100 °C, stir and mix for 30 min, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120 °C (3 h), 140 °C (5 h), and 160 °C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -29.2 °C.

[0044] Example 4

[0045] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.05 wt% hydroquinone were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. The nitrogen flow rate was set to 0.15 L / min, the magnetic stirring speed was set to 380 r / min, the reaction temperature was 160 °C, and the reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 2644, the weight-average molecular weight was 2807, and the polydispersity index was 1.06, determined by gel permeation chromatography (GPC, THF phase).

[0046] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 5 wt% zinc acetate to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.2. Under a nitrogen atmosphere, at a temperature of 100°C, stir and mix for 30 minutes, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120°C (3 h), 140°C (5 h), and 160°C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -28.6°C.

[0047] Example 5

[0048] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.2 wt% hydroquinone were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. Nitrogen gas flow rate was set to 0.15 L / min, magnetic stirring speed was set to 380 r / min, reaction temperature was 170 °C, and reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 2856, the weight-average molecular weight was 3138, and the polydispersity index was 1.09, determined by gel permeation chromatography (GPC, THF phase).

[0049] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 10 wt% zinc acetate to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.2. Under a nitrogen atmosphere, at a temperature of 100°C, stir and mix for 30 minutes, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120°C (3 h), 140°C (5 h), and 160°C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -26.9°C.

[0050] Example 6

[0051] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.5 wt% hydroquinone were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. The nitrogen flow rate was set to 0.15 L / min, the magnetic stirring speed was set to 380 r / min, the reaction temperature was 180 °C, and the reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 3210, the weight-average molecular weight was 3758, and the polydispersity index was 1.17, determined by gel permeation chromatography (GPC, THF phase).

[0052] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 20 wt% zinc acetate to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.2. Under a nitrogen atmosphere, at a temperature of 100°C, stir and mix for 30 minutes, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120°C (3 h), 140°C (5 h), and 160°C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -25.5°C.

[0053] Example 7

[0054] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.05 wt% 4-methoxyphenol were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. Nitrogen gas flow rate was set to 0.15 L / min, magnetic stirring speed was set to 380 r / min, reaction temperature was 190 °C, and reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 4800, the weight-average molecular weight was 5760, and the polydispersity index was 1.20, determined by gel permeation chromatography (GPC, THF phase).

[0055] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 5 wt% TBD to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.2. Under a nitrogen atmosphere, at a temperature of 100°C, stir and mix for 30 minutes, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120°C (3 h), 140°C (5 h), and 160°C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -24.6°C.

[0056] Example 8

[0057] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.2 wt% 4-methoxyphenol were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. Nitrogen gas flow rate was set to 0.15 L / min, magnetic stirring speed was set to 380 r / min, reaction temperature was 180 °C, and reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 3120, the weight-average molecular weight was 3245, and the polydispersity index was 1.04, determined by gel permeation chromatography (GPC, THF phase).

[0058] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 20 wt% TBD to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.2. Under a nitrogen atmosphere, at a temperature of 100 °C, stir and mix for 30 min, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120 °C (3 h), 140 °C (5 h), and 160 °C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -25.8 °C.

[0059] Example 9

[0060] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.2 wt% 4-methoxyphenol were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. Nitrogen gas flow rate was set to 0.15 L / min, magnetic stirring speed was set to 380 r / min, reaction temperature was 180 °C, and reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 3510, the weight-average molecular weight was 3720, and the polydispersity index was 1.06, determined by gel permeation chromatography (GPC, THF phase).

[0061] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 20 wt% TBD to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 1.6. Under a nitrogen atmosphere, at a temperature of 100 °C, stir and mix for 30 min, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120 °C (3 h), 140 °C (5 h), and 160 °C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -23.8 °C.

[0062] Example 10

[0063] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.2 wt% 4-methoxyphenol were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. Nitrogen gas flow rate was set to 0.15 L / min, magnetic stirring speed was set to 380 r / min, reaction temperature was 180 °C, and reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 3510, the weight-average molecular weight was 3720, and the polydispersity index was 1.06, determined by gel permeation chromatography (GPC, THF phase).

[0064] Weigh 10 grams of the above prepolymer, and add epoxidized soybean oil and 20 wt% TBD to a 100 ml three-necked flask according to an epoxy group to carboxyl group molar ratio of 2.2. Under a nitrogen atmosphere, at a temperature of 100 °C, stir and mix for 30 min, then pour into a polytetrafluoroethylene (PTFE) mold for curing. Then, place the PTFE mold in a vacuum oven purged with nitrogen, and cure at a stepped temperature increase of 120 °C (3 h), 140 °C (5 h), and 160 °C (5 h), finally obtaining a yellow transparent elastomer film with a glass transition temperature of -19.6 °C.

[0065] Comparative Example 1

[0066] 8.13 g (0.0625 mol) itaconic acid, 12.64 g (0.0625 mol) sebacic acid, 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, and 0.2 wt% 4-methoxyphenol were added to a 500 mL three-necked flask. Water generated during the reaction was collected using a water separator and condenser. Nitrogen gas flow rate was set to 0.15 L / min, magnetic stirring speed was set to 380 r / min, reaction temperature was 180 °C, and reaction time was 4 h, yielding a pale yellow carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The number-average molecular weight was 3510, the weight-average molecular weight was 3720, and the polydispersity index was 1.06, determined by gel permeation chromatography (GPC, THF phase).

[0067] 10 grams of the prepolymer were weighed, and 10 wt% of dicumyl peroxide (DCP) was added as a crosslinking agent to a three-necked flask. The temperature was set to 100°C, and the mixture was stirred and mixed for 30 minutes. The mixture was then poured into a polytetrafluoroethylene (PTFE) mold for curing. The PTFE mold was then placed in a nitrogen-filled vacuum oven, and the curing temperature was increased in stages: 120°C (3 hours), 140°C (5 hours), and 160°C (5 hours), ultimately yielding a yellow transparent elastomer film with a glass transition temperature of -11.3°C. This elastomer film could not achieve self-healing at low temperatures (-5°C).

[0068] Table 1 Performance Test Results

[0069] Tensile strength (MPa) Elongation at break (%) Tg (°C) Example 1 0.06 390 -29.8 Example 2 0.26 480 -29.9 Example 3 0.3 620 -29.2 Example 4 0.4 630 -28.6 Example 5 0.5 780 -26.9 Example 6 0.45 810 -25.5 Example 7 0.53 960 -24.6 Example 8 0.52 798 -25.8 Example 9 0.63 430 -23.8 Example 10 0.76 390 -19.6 Comparative Example 1 2.3 190 -11.3

[0070] Figure 1 This describes the preparation process for ultra-tough, low-temperature self-healing, reprocessed, and fully bio-based elastomers.

[0071] Figure 2 The image shows the scratch self-healing mechanism of the all-bio-based elastomer in Example 6. It can be seen that the obtained all-bio-based elastomer exhibits rapid self-healing ability at low temperatures; specifically, the scratch disappears within 12 hours at -5°C, demonstrating high self-healing efficiency.

[0072] Figure 3 This is a diagram showing the reprocessing of the all-bio-based elastomer in Example 6.

[0073] Figure 4 The stress-strain curves are those of the fully bio-based elastomer in Example 6 after reprocessing.

[0074] From Table 1 and Figure 1-3 As can be seen, the number-average molecular weight of the ultra-tough, low-temperature self-healing, reprocessable, and fully bio-based elastomer of this invention increases from 2644 to 3210 with increasing prepolymer preparation temperature, and the corresponding tensile strength increases from 0.06 MPa to 0.3 MPa. Furthermore, its elongation at break can reach up to 1200%, making it a suitable ultra-tough flexible material. Additionally, as the ratio of epoxy groups to carboxyl groups increases from 1 to 1.6, the tensile strength further increases from 0.3 MPa to 0.5 MPa, but the elongation at break decreases. Simultaneously, under the catalytic action of TBD, the ultra-tough, low-temperature self-healing, reprocessable, and fully bio-based elastomer of this invention can be reprocessed at 200°C. Moreover, due to its Tg close to -30°C and the presence of numerous H bonds, rapid self-healing at low temperatures is achieved.

[0075] Comparative Example 2 (Other reported self-healing crosslinked elastomers as controls)

[0076] In addition, other cross-linked elastomers reported previously were tested, and it was found that none of these cross-linked elastomers could achieve self-healing at low temperatures. For example:

[0077] Add 7.8 g (0.0625 mol) itaconic acid, 12.125 g (0.0625 mol) sebacic acid, 1.05 g (0.005 mol) 3,3-dithiodipropionic acid (DTPA), 3.8 g (0.05 mol) 1,3-propanediol, 4.5 g (0.05 mol) 1,4-butanediol, 0.27 g (0.003 mol) glycerol, and 0.5 wt% hydroquinone to a 500 mL three-necked flask. The water generated during the reaction was collected in a water tank and a condenser. Nitrogen gas flow was set at 0.15 L / min, the magnetic stirring speed was set at 380 r / min, the reaction temperature was 180℃, and the reaction time was 4 h. The esterification system was then replaced with a vacuum condensation system, and polycondensation was carried out at 220℃ and a vacuum of 100 Pa. To ensure complete cross-linking of the product, the reaction was terminated 3 h after the climbing effect occurred, ultimately yielding a yellow, transparent elastomer film with a glass transition temperature of -8.5℃. This elastomer cannot achieve self-healing at -5℃.

[0078] Example 11

[0079] Referring to Example 6, the reaction temperature in step (1) was adjusted and the molecular weight of the prepolymer was controlled, while other parameters remained unchanged, to obtain the corresponding elastomer film. The results are shown in Table 2.

[0080] Table 2

[0081]

[0082] As shown in the table above, controlling the molecular weight of the prepolymer by adjusting the reaction temperature results in a lower glass transition temperature, enabling excellent self-healing properties at low temperatures (-5℃); it also exhibits excellent mechanical properties. The optimal molecular weight is controlled at approximately 3210 at 180℃, achieving both excellent mechanical properties and low-temperature self-healing effect.

[0083] Example 12

[0084] Referring to Example 6, the molar ratio of epoxy groups to carboxyl groups in step (2) was adjusted, while other parameters remained unchanged, to obtain the corresponding elastomer film. The results are shown in Table 3.

[0085] Table 3

[0086]

[0087]

[0088] As can be seen from the table above, by adjusting the molar ratio of epoxy groups to carboxyl groups to control the degree of crosslinking, a lower glass transition temperature can be obtained while also exhibiting better mechanical properties.

[0089] Example 13 Reprocessing of All-Bio-Based Elastomers

[0090] The fully bio-based crosslinked elastomer from Example 6 was reprocessed. The elastomer was cut into fragments and then compressed at 200°C and 10 MPa for 3 minutes to obtain the reprocessed fully bio-based crosslinked elastomer. Notably, the fully bio-based crosslinked elastomer can be reprocessed multiple times with almost no loss of tensile strength after reprocessing, while the recovery rate of elongation at break is greater than 75%. Figure 3 This is attributed to the abundance of β-hydroxy esters in the fully bio-based crosslinked elastomer network, which provides numerous reaction sites for transesterification and demonstrates the effectiveness of dynamic covalent crosslinking network rearrangement in the fully bio-based crosslinked elastomer.

[0091] Table 4. Reprocessing properties of the fully bio-based crosslinked elastomers obtained in Example 6

[0092] Number of reprocessing times Tensile strength (MPa) Elongation at break (%) Tg (°C) 0 0.45 810 -25.5 1 0.39 600 -25.5 2 0.38 720 -25.3 3 0.38 660 -25.2

[0093] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A low-temperature self-healing bio-based elastomer, characterized in that, It is obtained by ring-opening polymerization of carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer and epoxidized soybean oil. Its topological structure contains a multiple dynamic network composed of H bonds and β-hydroxy ester bonds. The preparation method is as follows: (1) Synthesis of carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymers A bio-based dicarboxylic acid, a diol, and a polymerization inhibitor with a total acid-to-alcohol molar ratio of 1.05-2 are added to a reactor. The reaction temperature is 130-190℃ and the reaction time is 2-8 h to obtain a carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer. The bio-based dicarboxylic acids are itaconic acid and sebacic acid; the bio-based diols are 1,4-butanediol and 1,3-propanediol. (2) Chemical crosslinking The carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer in step (1) is melt-blended with epoxidized soybean oil and transesterification catalyst at 100~120℃ for 1~2 h, and then cured at 120~160℃ for 6~12 h to obtain a low-temperature self-healing bio-based elastomer. The molar ratio of epoxy groups in epoxidized soybean oil to carboxyl groups in carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymers is (1.0-2.2):

1.

2. The low-temperature self-healing bio-based elastomer according to claim 1, characterized in that, In step (1), the polymerization inhibitor is either 4-methoxyphenol or hydroquinone.

3. The low-temperature self-healing bio-based elastomer according to claim 1, characterized in that, In step (1), the molar ratio of diacid to diol is (1-2):1; the amount of polymerization inhibitor added relative to the total mass of diacid and diol is 0.05-0.5wt%.

4. The low-temperature self-healing bio-based elastomer according to claim 1, characterized in that, In step (1), the number average molecular weight of the carboxyl-terminated low molecular weight bio-based unsaturated aliphatic prepolymer is 1500-4800.

5. The low-temperature self-healing bio-based elastomer according to claim 1, characterized in that, In step (1), the reaction temperature is 150-180℃.

6. The low-temperature self-healing bio-based elastomer according to any one of claims 1-5, characterized in that, In step (2), the transesterification catalyst is any one of zinc acetate and 1,5,7-triazabicyclo[4.4.0]dec-5-ene; the amount of transesterification catalyst used is 5-20 mol of carboxyl content.

7. The application of the low-temperature self-healing bio-based elastomer according to any one of claims 1-6 in flexible wearable sensors.

8. The application of the low-temperature self-healing bio-based elastomer according to any one of claims 1-6 in the field of organic solar power generation.

9. The application of the low-temperature self-healing bio-based elastomer according to any one of claims 1-6 in the preparation of liquid crystal products, the preparation of biomedical materials, or electronic devices or equipment.

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