A repairable and recyclable biomass-based elastomer and a method for preparing the same

Abstract

The application provides a biomass-based elastic body which is repairable and recyclable and a preparation method thereof, and the steps are as follows: 1) preparation of maleimide grafted chitosan; 2) mixing maleimide grafted chitosan and furfuryl mercaptan modified vegetable oil polymer in a solvent, pouring the obtained mixed solution to obtain the biomass-based elastic body which is repairable and recyclable. The application selects vegetable oil and chitosan as a flexible matrix and a rigid skeleton respectively, and further introduces reversible D-A cross-linking bonds through structure design to prepare an elastic body material with adjustable topological structure and good mechanical properties. The rigid structure of chitosan guarantees the strength of the material, the fatty chain of vegetable oil makes it have good ductility and toughness, the reversible D-A bond makes the material have good thermal repair function, and the natural properties of raw materials endow the product with recyclable and renewable characteristics.

Description

Technical Field

[0001] This invention belongs to the field of bio-based functional polymer materials, specifically relating to a repairable and recyclable bio-based elastomer and its preparation method. Background Technology

[0002] Long-term use of polymer-based materials can lead to surface or internal structural damage from external forces and light radiation, resulting in cracks that significantly impair the material's functionality and lifespan. To improve material performance and extend its service life, the development of recyclable and repairable materials is progressing rapidly.

[0003] Self-healing polymer-based materials are a class of "smart" materials capable of self-repairing physical damage and restoring function, holding immense promise in the fields of materials science and engineering. Material self-healing can be achieved through either exogenous or intrinsic mechanisms. Using a carrier to deliver healing agents to repair damaged areas falls under the category of exogenous mechanisms; however, the limited precision and number of repair cycles hinders their development. In contrast, intrinsic repair primarily occurs through reversible dynamic cross-linking between polymer chains. Reversible cross-linking includes two main categories: weak interactions such as van der Waals forces, hydrogen bonds, and coordination, and covalent interactions such as DA bonds, borate ester bonds, and disulfide bonds. Among these, self-healing materials rich in reversible covalent bonds can repair damage while avoiding loss of their mechanical properties. Furthermore, the development and application of recyclable self-healing materials can address a global issue: delaying and reducing the amount of industrial waste, thereby reducing pollution from non-degradable petroleum-based products.

[0004] Given the increasingly severe resource crisis and environmental problems, and the recalcitrant nature of petrochemical-based materials, the reforming of renewable biomass feedstocks for use in chemicals and materials is considered an effective development direction for alleviating the crisis. Biomass mainly falls into two categories: the first category consists of natural polymers that can be used with minimal modification, such as cellulose, lignin, chitin, starch, proteins, and natural rubber; the second category comprises small biomolecules that can be structurally modified into monomers, such as plant oils, terpenes, rosin, furans, and amino acids. This diversity of small molecules will provide greater control over the properties of the synthesized bio-based polymers. Compared to petroleum-based materials, bio-based polymers have significant potential for improvement in mechanical properties, but their machinability is also limited (Progress in Polymer Science, 2020, 101:101197). Therefore, the development of recyclable bio-based materials (especially elastomers) requires clarifying the relationship between structure and properties, and implementing design and preparation based on the performance requirements of the materials.

[0005] Therefore, it is essential to develop repairable and recyclable biomass-based materials and optimize and overcome the mechanical performance defects of biomass derivatives. Summary of the Invention

[0006] The purpose of this invention is to provide a repairable and recyclable biomass-based elastomer and its preparation method. Vegetable oil and chitosan are selected as the flexible matrix and rigid framework, respectively. Further structural design introduces reversible DA crosslinking bonds, resulting in an elastomer material with a tunable topology and excellent mechanical properties. The rigid structure of chitosan ensures the material's strength, while the fatty chains of vegetable oil provide good ductility and toughness. The reversible DA bonds give the material excellent thermal repair capabilities, and the natural properties of the raw materials endow the product with recyclability and renewability.

[0007] The specific technical solution of this invention is as follows:

[0008] A method for preparing a repairable and recyclable biomass-based elastomer includes the following steps:

[0009] 1) Preparation of maleimide-grafted chitosan;

[0010] 2) Maleimide-grafted chitosan and furfuryl thiol-modified vegetable oil polymer are mixed in a solvent, and the resulting mixed solution is poured to obtain a repairable and recyclable biomass-based elastomer.

[0011] The preparation of maleimide-grafted chitosan in step 1) includes the following steps:

[0012] 1-1) Preparation of oil-soluble chitosan composed of sodium dodecyl sulfate;

[0013] 1-2) Sodium dodecyl sulfate-composite oil-soluble chitosan, 11-maleimide undecanoic acid and catalyst are mixed in a solvent, and dicyclohexylcarbodiimide solution is added dropwise to react.

[0014] Step 1-1) Preparation of oil-soluble chitosan composed of sodium dodecyl sulfate: sodium dodecyl sulfate solution is added dropwise to the chitosan solution under stirring, and the reaction is stirred.

[0015] In step 1-1), the mass concentration of the chitosan solution is 12-18 g / L; the mass concentration of the sodium dodecyl sulfate solution is 150-220 g / L; and the mass ratio of chitosan in the chitosan solution to sodium dodecyl sulfate in the sodium dodecyl sulfate solution is 1:3-4.

[0016] In step 1-1), the stirring reaction is carried out at room temperature for 3.5-5 hours.

[0017] In step 1-1), the solvents for both the chitosan solution and the sodium dodecyl sulfate solution are 2% (w / w) aqueous acetic acid solution, which is beneficial for dissolving chitosan.

[0018] In step 1-1), after stirring the reaction at room temperature, the filtered product is repeatedly washed with water and then further dried under vacuum to constant weight.

[0019] In steps 1-2), the mass ratio of dicyclohexylcarbodiimide in the sodium dodecyl sulfate composite oil-soluble chitosan, 11-maleimide undecanoic acid, catalyst, and dicyclohexylcarbodiimide solution is 1:0.7-0.8:0.06-0.08:0.5-0.7;

[0020] In steps 1-2), the catalyst is 4-dimethylaminopyridine;

[0021] In steps 1-2), the ratio of the amount of oil-soluble chitosan and solvent in the sodium dodecyl sulfate composite is 45-60 g / L;

[0022] In steps 1-2), the solvent is N,N-dimethylformamide (DMF);

[0023] In steps 1-2), the solvent for the dicyclohexylcarbodiimide solution is N,N-dimethylformamide (DMF); the concentration of the dicyclohexylcarbodiimide solution is 220-250 g / L.

[0024] In steps 1-2), the reaction is carried out at room temperature for 22-25 hours;

[0025] In steps 1-2), after the reaction is complete, the insoluble matter is filtered off, the filtrate is added dropwise to acetone to precipitate, filtered, the product is washed three times with acetone, and vacuum dried to obtain maleimide-grafted chitosan.

[0026] In step 2), maleimide-grafted chitosan accounts for 10-30% of the mass of the furfuryl thiol-modified vegetable oil polymer.

[0027] In step 2), the ratio of furfuryl thiol modified vegetable oil polymer to solvent is 0.08-0.18 g / mL;

[0028] In step 2), the solvent is N,N-dimethylformamide (DMF);

[0029] In step 2), the casting process involves casting the mixed solution into a polytetrafluoroethylene mold, evaporating it at 50°C for 48 hours, further drying it under vacuum, and then deepening the reaction at 65°C for 24 hours.

[0030] The preparation method of the furfuryl thiol modified vegetable oil polymer in step 2) includes the following steps:

[0031] A. Preparation of plant oil-derived monomers;

[0032] B. Preparation of vegetable oil-based polymers;

[0033] C. Preparation of furfuryl thiol-modified vegetable oil polymers.

[0034] The vegetable oil is selected from tung oil and soybean oil.

[0035] Step C specifically involves:

[0036] A vegetable oil-based polymer, furfuryl thiol, and azobisisobutyronitrile (AIBN) were mixed in a solvent, and the mixture was heated under an inert atmosphere in a sealed environment.

[0037] The mass ratio of the vegetable oil-based polymer to azobisisobutyronitrile in step C is 60-70:1;

[0038] In step C, the ratio of vegetable oil-based polymer to furfuryl mercaptan is 0.5-0.6 g / mL;

[0039] The ratio of the vegetable oil-based polymer to the solvent in step C is 0.25-0.35 g / mL;

[0040] The inert atmosphere mentioned in step C is nitrogen or argon;

[0041] The solvent mentioned in step C is tetrahydrofuran (THF);

[0042] The sealed heating reaction described in step C is carried out at a temperature of 65±5℃ for 10-14 hours.

[0043] In step C, after the reaction, the mixture is cooled to room temperature and purified by dichloromethane-methanol precipitation, followed by vacuum drying to obtain furfuryl thiol modified vegetable oil polymer.

[0044] The furfuryl thiol-modified vegetable oil polymer mentioned in step C is preferably a furfuryl thiol-modified tung oil-based polymer or a furfuryl thiol-modified soybean oil-based polymer.

[0045] The present invention provides a repairable and recyclable biomass-based elastomer, which is prepared by the above method.

[0046] Vegetable oils, as a common type of biomass, are diverse, high-yielding, rich in modifiable active groups, and have a wide range of applications. Therefore, developing vegetable oils and converting them into high-performance petroleum-based material substitutes has become a highly competitive research area for institutions worldwide. The triglyceride structure of natural vegetable oils contains modifiable groups such as double bonds, hydroxyl groups, and ester groups, which is beneficial for constructing structural units with different functionalities to achieve large-scale preparation of thermoplastic or thermosetting bio-based materials. To overcome the mechanical weaknesses of vegetable oil-derived materials, chitosan, with its rigid structure, is introduced for composite reinforcement. Simultaneously, the abundant functional groups carried by chitosan can be used for functionalization.

[0047] Chitosan, a linear polycationic polysaccharide found in abundance in nature after cellulose, possesses excellent biocompatibility and biodegradability, as well as good antibacterial and film-forming properties. Therefore, chitosan has broad applications in tissue engineering, drug and gene delivery, and antibacterial fillers; it also holds immense potential for development and application in bioplastics, renewable elastomers, and green adhesives.

[0048] To develop biomass materials that can replace petrochemical resources, and to optimize and overcome the inherent mechanical defects of biomass derivatives, this invention selects vegetable oil and chitosan as the flexible matrix and rigid framework, respectively. Using these two types of structurally modified biomass polymers, a repairable elastomer is constructed based on DA crosslinking. Further structural design introduces reversible DA crosslinking bonds, resulting in an elastomer material with a tunable topology and excellent mechanical properties. The dynamic DA covalent bonds within the elastomer network provide the material's repairability, while the natural properties of the raw materials endow the product with recyclability and renewability.

[0049] Compared with existing technologies, this invention prepares a flexible polymer with abundant side chains by recombining and resolving vegetable oil molecules into macromonomers and then performing free radical polymerization. "Click chemistry" is used to introduce furan groups into the mid-position of double bonds in the side chains. Furthermore, a relatively long maleimide group is attached to chitosan via esterification. Based on the Diels-Alder addition reaction between furan and maleimide groups, a biomass-based elastomer with dynamically reversible covalent bonds is simply constructed. With the increase of the rigid chain of chitosan, the crosslinking density also increases, and the strength of the elastomer significantly increases. This invention, combining the resource characteristics of the raw materials, prepares a repairable elastomer material based on dynamic crosslinking using a low-entanglement molecular weight polymer and rigid chitosan chains, expanding the development and application scope of sustainable biomass functional materials. Attached Figure Description

[0050] Figure 1 The 1H NMR spectrum of sodium dodecyl sulfate-based chitosan (bottom) and maleimide-grafted chitosan (top) are shown.

[0051] Figure 2 The 1H NMR spectrum of furfuryl thiol-modified tung oil-based polymer (PTOMF);

[0052] Figure 3 The 1H NMR spectrum of soybean oil-based polymer (PSBMF) modified with furfuryl thiol;

[0053] Figure 4 Stress-strain curves of chitosan-tung oil elastomers (CS-PTOMF) with different proportions;

[0054] Figure 5Differential scanning calorimetry curves of chitosan-tung oil elastomers (CS-PTOMF) with different proportions;

[0055] Figure 6 Differential scanning calorimetry curves of CS-PTOMF / 20 elastomer before and after repair;

[0056] Figure 7 Stress-strain curves of CS-PTOMF / 20 elastomer before and after repair;

[0057] Figure 8 The reaction equation for the preparation of oil-soluble chitosan;

[0058] Figure 9 The reaction equation for the synthesis of maleimide-grafted chitosan is shown below.

[0059] Figure 10 Flowchart of the synthesis of tung oil-based polymer modified with furfuryl thiol;

[0060] Figure 11 Flowchart of the synthesis of soybean oil-based polymers modified with furfuryl thiol;

[0061] Figure 12 A schematic diagram of the preparation and reverse process of repairable chitosan-tung oil elastomer;

[0062] Figure 13 Photographs showing the repairability test results of chitosan-tung oil elastomer. Detailed Implementation

[0063] Example 1

[0064] A method for preparing a repairable and recyclable biomass-based elastomer includes the following steps:

[0065] 1) Preparation of maleimide-grafted chitosan (CS-MUA):

[0066] 1-1) Dissolve 16 g of chitosan (molecular weight approximately 40 kDa, degree of deacetylation >90%) in 1 L of 2% acetic acid solution to obtain a chitosan solution. While stirring, add 300 mL of 2% acetic acid solution containing 57 g of sodium dodecyl sulfate dropwise to the chitosan solution system at room temperature for 4 hours. Afterward, filter the product, wash repeatedly with water, and further vacuum dry to constant weight; the reaction equation is as follows. Figure 8 As shown; the results confirmed by 1H NMR spectroscopy are that it is an oil-soluble chitosan complexed with sodium dodecyl sulfate, such as... Figure 1 As shown in the image below. 1 ¹H NMR (DMSO-d6, δ, ppm): 5.33 (H a ),4.69(H p ), 3.68-3.47(Hc H d H e H f ),2.85(H b ), hydrogens at different positions in the chitosan backbone structure; 3.7(H k ),1.48(H j ),1.24(H h ), belonging to sodium dodecyl sulfate, with methylene hydrogen located furthest from the sulfate group, 0.85 (H g Methyl hydrogen is attributed to sodium dodecyl sulfate.

[0067] Step 1-1) makes chitosan oil-soluble (electrostatic complexation) and at the same time improves the compatibility of chitosan chains with subsequent plant oil-based polymers.

[0068] 1-2) Dissolve 10 g of the oil-soluble chitosan prepared above in 100 mL of dry N,N-dimethylformamide (DMF). Dissolve 7.76 g of 11-maleimide undecanoic acid and 0.7 g of 4-dimethylaminopyridine (DMAP) in 100 mL of dry DMF, and mix the two solutions by stirring. Further, add 25 mL of DMF solution containing 6 g of dicyclohexylcarbodiimide (DCC) dropwise to the system with stirring. After reacting at room temperature for 24 hours, filter out the insoluble matter, precipitate the filtrate in acetone, filter, wash the product three times with acetone, and dry under vacuum. The reaction equation is as follows: Figure 9 As shown; the product characterized by 1H NMR spectroscopy is maleimide-grafted chitosan, such as... Figure 1 As shown in the image above. 1 ¹H NMR (DMSO-d6, δ, ppm): 7.0 (H r ) and 2.17(H q The peaks at () represent the hydrogen peaks of the double bond on the five-membered ring and the methylene hydrogen of the adjacent ester bond of the grafted maleimide undecanoic acid.

[0069] Steps 1-2) involve grafting long-chain maleimide onto the chitosan backbone (esterification reaction) to provide maleimide groups for the subsequent DA reaction with the vegetable oil-based polymer. Furthermore, this also provides a rigid chain structure for the mechanical strength of the all-biomass elastomer.

[0070] 2) Preparation of furfuryl thiol-modified tung oil-based polymer (PTOMF)

[0071] 2-1) 100 g of tung oil was heat-treated at 105 °C for 1 hour under nitrogen atmosphere. After cooling to 60 °C, 33.5 g of N-methylethanolamine and 1.5 mL of sodium methoxide solution (30 wt%) were added, and stirring was continued at 60 °C for 5 hours. The crude product was diluted with 200 mL of dichloromethane (DCM), washed three times with saturated brine, and the organic phase was dried over anhydrous magnesium sulfate. The solvent was then removed by vacuum distillation to obtain a pure yellow liquid.

[0072] Take 102 g of the prepared yellow liquid, add 50 g of methacrylic anhydride and 0.4 g of 4-dimethylaminopyridine (DMAP), seal and heat to 60 °C with stirring for 12 hours. Then, add 20 mL of deionized water and 30 mL of tetrahydrofuran (THF), stir for 4 hours, and transfer to DCM. Wash twice with saturated sodium bicarbonate and once with saturated brine. After drying with anhydrous magnesium sulfate, distill under reduced pressure to obtain pure tung oil-derived monomer (TOMA).

[0073] 2-2) Dissolve 15 g of tung oil derivative monomer TOMA in 15 mL of toluene, add 60 mg of azobisisobutyronitrile (AIBN) while stirring, and stir at 80 °C for 20 hours under nitrogen protection after complete dissolution. After the reaction is complete, remove the residue and solvent by dichloromethane-methanol precipitation, and dry to obtain tung oil-based polymer (PTOM).

[0074] 2-3) 8.2 g of tung oil-based polymer PTOM, 16 mL of furfuryl mercaptan, and 130 mg of azobisisobutyronitrile (AIBN) were dissolved in 30 mL of dry THF. After bubbling with nitrogen for 15 minutes, the mixture was sealed and heated to 65 °C for 12 hours. After cooling to room temperature, the mixture was purified by dichloromethane-methanol precipitation and vacuum dried to obtain furfuryl mercaptan-modified tung oil-based polymer (PTOMF). Its 1H NMR spectrum is shown below. Figure 2 As shown, 1 H NMR(CDCl3,δ,ppm):6.04-5.28(H k H m H n The range 3.22 (H) represents the proton peak of the remaining double bond in the tung oil side chain of the polymer; h ) belongs to the nitrogen-methyl peak (N-CH3); 2.23 (H j The peak at 7.28 (H) represents the methylene proton peak adjacent to the amide bond. d ),6.22(H c ),6.09(H b The peaks are attributed to protons on the furan ring grafted onto the side chain; 3.59 (H) a The peak () represents the methylene proton peak connecting furan and sulfur. The structural formula of the tung oil-based polymer (PTOMF) is:

[0075]

[0076] Figure 10 The flowchart shows the synthesis of tung oil-based polymer modified with furfuryl thiol. In step 2), the synthesized tung oil-based polymer provides the flexible structure of the subsequent elastomer through free radical polymerization. Furthermore, furan groups are incorporated into the polymer via a "click chemistry" reaction between the thiol group of furfuryl thiol and the double bonds of the tung oil-based polymer side chain. Simultaneously, the furan groups carried by the polymer side chain provide conjugated double bonds for the subsequent DA reaction.

[0077] 3) Preparation of repairable chitosan-tung oil elastomer (CS-PTOMF)

[0078] 2.4 g of tung oil-based polymer PTOMF was dissolved in 5 mL of DMF, and then mixed with 10 mL of DMF solution containing 0.24 g of maleimide-grafted chitosan. After thorough mixing and degassing, the homogeneous mixture was cast into a polytetrafluoroethylene mold. The mixture was allowed to evaporate at 50 °C for 48 hours, and then further dried under vacuum before being reacted at 65 °C for 24 hours. A film with a thickness of 0.2 mm was obtained, which was a CS-PTOMF / 10 elastomer.

[0079] Figure 12 A schematic diagram of the preparation and reverse process of repairable chitosan-tung oil elastomer;

[0080] In step 3), the plant oil-based polymer and chitosan derivative form a cross-linked network of two polymer chains via a DA reaction, which is the biomass elastomer. The rigid chains of chitosan provide the mechanical strength of the elastomer, while the flexible plant oil chains provide toughness and ductility. Furthermore, DA cross-linking also enhances the strength of the elastomer; the higher the cross-linking density, the greater the increase in material strength, as confirmed by the differential scanning calorimetry (DSC) curves of elastomers with different chitosan contents. On the other hand, the DA covalent bonds that construct the network exhibit reversible decomposition at higher temperatures and rebonding upon heating, giving the prepared elastomer a repairable function.

[0081] The results of the CS-PTOMF / 10 elastomer mechanical property test (test standard: GB / T1040.1-2018) are as follows: Figure 4 As shown, the stress on the elastomer is 1.7 MPa, and the corresponding fracture strain reaches approximately 115%.

[0082] The preparation was carried out according to Example 1, except that the ratio of PTOMF and CS-MUA raw materials was changed. The specific experiment is as follows:

[0083] 2.4 g of tung oil-based polymer PTOMF was dissolved in 5 mL of DMF, and then mixed with 15 mL of DMF solution containing 0.48 g of CS-MUA. After thorough mixing and degassing, the homogeneous mixture was cast into a polytetrafluoroethylene mold. The mixture was allowed to evaporate at 50 °C for 48 hours, and then further dried under vacuum before being reacted at 65 °C for 24 hours. A film with a thickness of 0.2 mm was obtained, which was a CS-PTOMF / 20 elastomer. The mechanical properties were tested as follows. Figure 4 As shown, the stress on the elastomer is 3.9 MPa, and the corresponding fracture strain reaches approximately 57%.

[0084] 2.4 g of tung oil-based polymer PTOMF was dissolved in 5 mL of DMF, and then mixed with 20 mL of DMF solution containing 0.72 g of CS-MUA. After thorough mixing and degassing, the homogeneous mixture was cast into a polytetrafluoroethylene mold. The mixture was allowed to evaporate at 50 °C for 48 hours, and then further dried under vacuum before being reacted at 65 °C for 24 hours. A film with a thickness of 0.21 mm was obtained, which was a CS-PTOMF / 30 elastomer. The mechanical properties were tested as follows. Figure 4 As shown, the stress on the elastomer reaches 8.2 MPa, while the corresponding fracture strain is approximately 63%.

[0085] Differential scanning calorimetry analysis showed that with the increase of CS-MUA dosage, the glass transition temperature of the prepared elastomer gradually increased from 25.2℃ to 30.1℃. Figure 5 (As shown). The mechanical properties of the above three biomass elastomers demonstrate that increasing the content of the chitosan rigid structure and increasing the DA crosslinking density of the two bio-based polymers will lead to a decrease in the elastomer's fracture strain, while simultaneously significantly increasing the material's strength. Appropriate chitosan composite content will be beneficial for preparing high-toughness biomass elastomers.

[0086] Example 2

[0087] A method for preparing a repairable and recyclable biomass-based elastomer includes the following steps:

[0088] 1) Preparation of maleimide-grafted chitosan (CS-MUA): Same as in Example 1;

[0089] 2) Preparation of soybean oil-based polymer modified with furfuryl thiol (PSBMF):

[0090] 2-1) 100 g of soybean oil was heat-treated at 101 °C for 1 hour under nitrogen atmosphere. After cooling to 60 °C, 33 g of N-methylethanolamine and 1.5 mL of sodium methoxide solution (30 wt%) were added, and stirring was continued at 60 °C for 5 hours. The crude product was diluted with 200 mL of dichloromethane (DCM), washed three times with saturated brine, and the organic phase was dried over anhydrous magnesium sulfate. The solvent was removed by vacuum distillation to obtain a pure, light yellow liquid.

[0091] Take 102 g of the intermediate solution prepared above, add 49.5 g of methacrylic anhydride and 0.4 g of DMAP, seal and heat to 60 °C with stirring for 12 hours. Then, add 20 mL of deionized water and 30 mL of tetrahydrofuran (THF), stir for 4 hours and transfer to DCM, wash twice with saturated sodium bicarbonate and once with saturated brine. After drying with anhydrous magnesium sulfate, distill under reduced pressure to obtain pure soybean oil-derived monomer (SBMA).

[0092] 2-2) Dissolve 15 g of soybean oil derivative monomer SBMA in 15 mL of toluene, add 50 mg of azobisisobutyronitrile (AIBN) while stirring, and stir at 80 °C for 12 hours under nitrogen protection after complete dissolution. After the reaction is complete, remove the residue and solvent by dichloromethane-methanol precipitation, and dry to obtain soybean oil-based polymer (PSBM).

[0093] 2-3) Dissolve 8.2 g of polymer PSBM, 16 mL of furfuryl thiol, and 130 mg of AIBN in 25 mL of dry THF. After bubbling with nitrogen for 15 minutes, seal and heat to 65°C for 12 hours. After cooling to room temperature, purify by dichloromethane-methanol precipitation and vacuum dry to obtain furfuryl thiol-modified soybean oil-based polymer (PSBMF). Its 1H NMR spectrum is shown below. Figure 3 As shown, 1 H NMR(CDCl3,δ,ppm):5.39-5.35(H k The range 3.1 (H) represents the proton peak of the remaining double bond in the soybean oil side chain of the polymer; h ) belongs to the nitrogen-methyl peak (N-CH3); 2.33 (H j ) is the methylene proton peak near the amide bond; 7.35 (H) d ),6.3(H c ),6.17(H b The proton peaks 3.71 (H) are respectively attributed to the proton peaks on the furan ring grafted onto the side chain; a The peak () represents the methylene proton connecting furan and sulfur. The structural formula is:

[0094] Figure 11 Flowchart of the synthesis of soybean oil-based polymers modified with furfuryl thiol;

[0095] In step 2), the synthesized soybean oil-based polymer, obtained through free radical polymerization, provides the flexible structure for the subsequent elastomer. Furthermore, furan groups are incorporated into the polymer via a "click chemistry" reaction between the thiol group of furfuryl thiol and the double bonds of the soybean oil-based polymer side chains. Simultaneously, the furan groups carried by the polymer side chains provide conjugated double bonds for the subsequent DA reaction.

[0096] 3) Preparation of repairable chitosan-soybean oil elastomer (CS-PSBMF)

[0097] 2.4 g of soybean oil-based polymer PSBMF was dissolved in 5 mL of DMF, and then mixed with 15 mL of DMF solution containing 0.48 g of maleimide-grafted chitosan. After thorough mixing and degassing, the homogeneous mixture was cast into a polytetrafluoroethylene mold. The mixture was allowed to evaporate at 50 °C for 48 hours, and then further dried under vacuum before being reacted at 65 °C for 24 hours. A film with a thickness of 0.2 mm was obtained, which was a CS-PSBMF / 20 elastomer.

[0098] Example 3

[0099] Repairability test of chitosan-tung oil elastomer:

[0100] CS-PTOMF / 20 elastomer was randomly sheared into small fragments, which were then hot-pressed at 170℃ and 15MPa for 10 minutes to reshape a monolithic elastic material, denoted as CS-PTOMF / 20-R. Differential scanning calorimetry (DSC) and tensile mechanical tests were performed on the reshaped material, and the results were compared with those of the original elastic material. The reshaping process failed to fully restore the DA crosslinks, leading to a decrease in crosslink density. Therefore, the glass transition temperature of the repaired material was significantly lower. Figure 6 As shown. However, the presence of the rigid structure of chitosan ensures that the mechanical properties of the elastomer do not change significantly, such as... Figure 7 As shown, compared to the original elastomer, the stress of the repaired material decreased by only 20%, while the strain increased by 27%. This indicates that rigid-modified chitosan can be crosslinked with tung oil-based polymers via dynamic DA bonds to prepare elastomers with good repair properties while maintaining the mechanical properties of the repaired material. Figure 13 Photographs showing the repairability test results of chitosan-tung oil elastomer.

[0101] In this invention, chitosan is modified by grafting long-chain maleimide, obtaining maleimide groups that can be used in DA reactions while further improving the compatibility of chitosan with subsequent polymers. The rigid structure of chitosan ensures the strength of the material, while the fatty chains of vegetable oil give it good ductility and toughness. By using two biomass polymers with different structural characteristics (rigid chain and flexible chain) through DA bonds, a repairable elastomer is prepared. The reversible DA bonds give the material good thermal repair function, and the natural properties of the raw materials endow the product with recyclable and renewable characteristics.

Claims

1. A method for preparing a repairable and recyclable biomass-based elastomer, characterized in that, The preparation method includes the following steps: 1) Preparation of maleimide-grafted chitosan; 2) Maleimide-grafted chitosan and furfuryl thiol-modified vegetable oil polymers are mixed in a solvent, and the resulting mixed solution is cast to obtain a repairable and recyclable biomass-based elastomer. The preparation of maleimide-grafted chitosan in step 1) includes the following steps: 1-1) Preparation of oil-soluble chitosan complexed with sodium dodecyl sulfate; 1-2) Sodium dodecyl sulfate-complexed oil-soluble chitosan, 11-maleimide undecanoic acid and catalyst are mixed in a solvent, and dicyclohexylcarbodiimide solution is added dropwise to react; The preparation method of the furfuryl thiol modified vegetable oil polymer in step 2) includes the following steps: A. Preparation of plant oil-derived monomers; B. Preparation of vegetable oil-based polymers; C. Preparation of furfuryl thiol-modified vegetable oil polymer: Vegetable oil-based polymer, furfuryl thiol and azobisisobutyronitrile (AIBN) are mixed in a solvent and heated under an inert atmosphere.

2. The preparation method according to claim 1, characterized in that, Step 1-1) Preparation of oil-soluble chitosan composed of sodium dodecyl sulfate: sodium dodecyl sulfate solution is added dropwise to the chitosan solution under stirring, and the reaction is stirred.

3. The preparation method according to claim 1, characterized in that, In steps 1-2), the mass ratio of dicyclohexylcarbodiimide in the sodium dodecyl sulfate composite oil-soluble chitosan, 11-maleimide undecanoic acid, catalyst and dicyclohexylcarbodiimide solution is 1:0.7-0.8:0.06-0.08:0.5-0.

7.

4. The preparation method according to claim 1 or 3, characterized in that, In steps 1-2), the catalyst is 4-dimethylaminopyridine.

5. The preparation method according to claim 1, characterized in that, In step 2), maleimide-grafted chitosan accounts for 10-30% of the mass of the furfuryl thiol-modified vegetable oil polymer.

6. The preparation method according to claim 1, characterized in that, The sealed heating reaction described in step C is carried out at a temperature of 65±5℃ for 10-14 hours.

7. The preparation method according to claim 1 or 6, characterized in that, In step C, the mass ratio of the vegetable oil-based polymer to azobisisobutyronitrile is 60-70:1; the ratio of the vegetable oil-based polymer to furfuryl mercaptan is 0.5-0.6 g / mL.

8. A repairable and recyclable biomass-based elastomer prepared by the preparation method according to any one of claims 1-7.

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