Shape memory polymer based on bottlebrush structure and preparation method thereof

Abstract

The application relates to the technical field of high polymer materials, and discloses a bottle-brush structure-based shape memory polymer and a preparation method thereof, which comprises the following steps: dissolving a polycaprolactone precursor modified by thioctic acid at two ends in a good solvent to prepare a polymer solution, and irradiating the polymer solution with ultraviolet light in a mold to induce the photo-dimerization reaction of thiolane groups at the chain ends of the polymer to crosslink and polymerize the polymer into a product, and complete the structure construction of a covalent self-adapting network rich in dynamic disulfide bonds. The bottle-brush crosslinking network is constructed by adopting a photo-induced disulfide bond crosslinking mechanism, the material can be solidified and formed at room temperature, and the thermal degradation of the polymer main chain caused by high temperature is avoided; meanwhile, the dynamic exchange mechanism of the disulfide bond is utilized, the polymer network can be degraded and regenerated, and the problems that a conventional shape memory polymer cannot be reshaped after being formed and cannot be recycled by chemical closed loop are solved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a shape memory polymer based on a bottle brush structure and its preparation method. Background Technology

[0002] Shape memory polymers (CMPs) can recover from a temporary shape to a pre-set permanent shape under external environmental stimuli, making them suitable for applications in flexible electronics, biomedical devices, and smart structural components. Traditional CCMs typically rely on a permanent chemical cross-linking network to maintain the structural stability of their initial shape. This permanent cross-linking network results in the material being insoluble and infusible after curing. When such materials experience structural damage or reach their lifespan, they cannot be reshaped or chemically recycled through heating, melting, or solvent dissolution, ultimately leading to their disposal as solid waste and resulting in material waste.

[0003] To endow crosslinked polymers with processability and recyclability, existing technologies typically introduce dynamic covalent bonds into the polymer network to construct covalently adaptive networks. However, current fabrication processes for these dynamic crosslinked networks largely rely on high-temperature thermosetting conditions. For shape memory materials with aliphatic polyesters such as polycaprolactone as the flexible backbone, prolonged high-temperature treatment can easily induce thermal degradation of the polyester backbone, leading to a decline in the material's fundamental mechanical properties.

[0004] Meanwhile, conventional direct crosslinking methods struggle to precisely control the microstructure of polymers, and the randomness of crosslinking point distribution can lead to unstable shape fixation and recovery rates at room temperature. Furthermore, existing dynamic crosslinking systems often face incomplete degradation or difficulty in separating decrosslinking products when attempting chemical closed-loop recycling. The recovered polymer precursors are difficult to re-establish a regular crosslinking network during secondary processing, resulting in a significant decrease in the mechanical strength and shape memory effect of the recycled materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a shape memory polymer based on a bottle brush structure and its preparation method. This solves the problem that existing shape memory polymers typically employ permanent chemical crosslinking networks, which prevents the materials from being reshaped, repaired, or chemically recycled after curing, resulting in material waste. Furthermore, polymers that conventionally introduce dynamic covalent bonds often suffer from difficulties in precisely controlling the crosslinking density and unstable mechanical properties at room temperature.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a shape memory polymer based on a bottle brush structure and its preparation method, comprising: In a first aspect, the present invention provides a shape memory polymer based on a bottle brush-like structure, employing the following technical solution: The polymer is a covalently adaptive network crosslinked structure rich in dynamic disulfide bonds. The polymer is prepared by dissolving a polycaprolactone precursor modified with thioctic acid at both ends in a good solvent to form a polymer solution, and then inducing photodimerization and crosslinking polymerization of the thiocyclopentyl groups at the ends of the polymer chains in a mold under ultraviolet light irradiation, thus completing the spatial structure construction of the covalently adaptive network.

[0007] The polycaprolactone precursor modified with lipoic acid at both ends is prepared by chemical reaction of polycaprolactone diol, lipoic acid, 4-dimethylaminopyridine and N,N'-dicyclohexylcarbodiimide in a mass ratio of 1200-1300:90-120:50-80:90-120, wherein lipoic acid modifies both ends of the polycaprolactone diol and provides terminal thiohexylcyclopentyl groups.

[0008] The polycaprolactone diol is prepared by mixing ε-caprolactone monomer, diethylene glycol, and dibutyltin oxide in a mass ratio of 400:11-15:1-4 and reacting them under oil bath heating conditions. The good solvent is selected from chloroform, dichloromethane, or tetrahydrofuran.

[0009] By employing the above technical solution, this invention utilizes a photoinduced disulfide bond ring-opening crosslinking mechanism to construct a covalent adaptive network with a bottle-brush-like structure, achieving a combination of shape memory function and recyclability. The specific reaction mechanism and spatial structure construction process are as follows: Step 1: Ring-opening polymerization to generate the main chain segment: Under the action of dibutyltin oxide catalyst, diethylene glycol is used as an initiator to initiate the ring-opening polymerization of ε-caprolactone monomer. The reaction generates linear polycaprolactone diol with a certain degree of polymerization. This polycaprolactone segment serves as the flexible main chain of the final crosslinked network, providing the material with crystallinity and deformability at room temperature.

[0010] Step two, end-group esterification modification reaction: Using N,N'-dicyclohexylcarbodiimide as a dehydrating condensing agent and 4-dimethylaminopyridine as a catalyst, the carboxyl group of lipoic acid undergoes an esterification reaction with the terminal hydroxyl group of polycaprolactone diol. This step grafts a thiohexacyclopentane group containing a dynamic five-membered ring disulfide bond to both ends of the polycaprolactone chain, forming a polycaprolactone precursor with active end groups.

[0011] Step 3, photo-induced ring-opening crosslinking reaction: After spreading the above precursor in a mold, under ultraviolet light excitation, the thiohexacyclic pentyl groups at the ends of the precursor absorb light energy, causing the release of the inherent ring strain within, resulting in photo-ring-opening polymerization and dimerization. Disulfide bonds at adjacent chain ends break and recombine, crosslinking to form a stable three-dimensional covalent adaptive network. This network structure, with polycaprolactone as the backbone and disulfide bonds as crosslinking nodes, exhibits a bottle-brush-like micro-crosslinking morphology from a spatial topological perspective. The abundant dynamic disulfide bonds within the network enable the polymer to undergo topological rearrangement under external stimuli, endowing the material with shape memory effect and processability.

[0012] Preferably, the mass ratio of polycaprolactone diol, thioctic acid, 4-dimethylaminopyridine, and N,N'-dicyclohexylcarbodiimide is 1250:105:65:105; and the mass ratio of ε-caprolactone monomer, diethylene glycol, and dibutyltin oxide is 400:13:2.5.

[0013] By employing the above technical solution, the specific mass ratio controls the molar ratio of initiator to monomer in the polymerization system, thereby regulating the molecular weight and crystallinity of the flexible polycaprolactone segments. Simultaneously, the specific ratio of dehydrating condensing agent and catalyst ensures the esterification conversion rate of the terminal hydroxyl groups, guaranteeing sufficient active crosslinking groups at both ends of the precursor, thus achieving a crosslinking density with suitable mechanical properties.

[0014] Preferably, the preparation process of the polycaprolactone precursor modified with thioctic acid at both ends is as follows: the polycaprolactone diol, thioctic acid, 4-dimethylaminopyridine and N,N'-dicyclohexylcarbodiimide are placed in a flask, the good solvent is added and ultrasonically vibrated to dissolve and mix evenly, and then heated in an oil bath at 15-35°C for 20-30 hours. After filtering to remove the generated by-product precipitate, the filtrate is dropped into a poor solvent selected from n-hexane, cyclohexane or methanol to precipitate, the precipitate is filtered and dried under vacuum to obtain the product.

[0015] By adopting the above technical solution, a phase transformation process combining good solvent dissolution with poor solvent precipitation can be used to remove unreacted free thioctic acid, catalysts, and byproducts such as dicyclohexylurea produced by condensation, thereby obtaining a high-purity precursor polymer and preventing impurity molecules from quenching or causing micro-phase separation during subsequent UV curing.

[0016] Preferably, the preparation process of the polycaprolactone diol is as follows: under nitrogen protection, the ε-caprolactone monomer, diethylene glycol and dibutyltin oxide are placed in a flask and continuously stirred and heated in an oil bath at 120-150°C for 5-10 hours. After cooling, it is mixed with the good solvent, dropped into a poor solvent selected from n-hexane, cyclohexane or methanol to precipitate and stand. The precipitate is then filtered and dried under vacuum to obtain the product.

[0017] By adopting the above technical solution, ring-opening polymerization under anaerobic high-temperature conditions can suppress the occurrence of side reactions, ensure the uniformity of polymer molecular weight distribution, and lay the structural foundation for the subsequent formation of a regular covalent adaptive network.

[0018] Secondly, this invention provides a method for preparing shape memory polymers based on a bottle brush-like structure, employing the following technical solution: A method for preparing a shape memory polymer based on a bottle brush structure includes the following steps: dissolving a polycaprolactone precursor modified with thioctic acid at both ends in a good solvent to prepare a precursor polymer solution; subjecting the precursor polymer solution to ultrasonic vibration to dissolve and mix it uniformly; pouring the uniformly mixed precursor polymer solution into a mold to form a precursor film; subsequently irradiating the precursor film with ultraviolet light to induce photodimerization of the terminal thiocyclopentyl groups, thereby forming a crosslinked network containing dynamic disulfide bonds; and obtaining the shape memory polymer based on the bottle brush structure after irradiation.

[0019] By adopting the above technical solution and using a process path combining solution casting and ultraviolet curing, polymerization can be initiated at room temperature without high-temperature heat treatment. This avoids the potential localized thermal degradation of the polycaprolactone backbone caused by high temperatures, making the film formation process easier to control and suitable for preparing polymeric material devices with complex shapes.

[0020] Preferably, the concentration of the precursor polymer solution is 0.01–0.1 g / mL, and the ultrasonic oscillation time is 0.2–1 h; when performing ultraviolet irradiation, the distance between the ultraviolet light source and the mold surface is fixed at 1.5–3 cm, and the ultraviolet irradiation time is 0.5–1.5 h.

[0021] By adopting the above technical solution, the matching of the solution concentration and illumination parameters ensures that the polymer solution has a suitable viscosity for smooth film spreading. A fixed illumination distance and time allow the ultraviolet photons to penetrate to cover the entire thickness of the film, ensuring a consistent rate of disulfide bond ring-opening crosslinking reactions on the upper and lower surfaces and inside the film, thus avoiding stress concentration and warping caused by uneven curing.

[0022] Preferably, the process includes a chemical recovery process for a covalent adaptive network, in which the obtained polymer is chopped into fragments and immersed in a good solvent to allow it to swell fully; an aqueous solution of sodium borohydride is added to the swollen gel, and the mixture is stirred at room temperature until a homogeneous polymer solution is formed after degradation; subsequently, a mixture of a good solvent containing copper chloride and deionized water is added dropwise to the homogeneous polymer solution after degradation to catalyze oxidation and dynamic exchange reactions; the mixture is filtered to remove insoluble matter; the filtrate containing the recovered substance is added dropwise to a poor solvent for precipitation, and the polymer obtained from the precipitation is collected by filtration, washed, and vacuum dried to obtain a powder. The catalytic oxidation and dynamic exchange reactions are carried out at room temperature for 20-30 hours, and the poor solvent is selected from n-hexane, cyclohexane, or methanol; the recovered powder is redissolved in a good solvent to prepare a solution, and the solution is obtained by ultrasonic vibration and ultraviolet irradiation to obtain a regenerated polymer.

[0023] By adopting the above technical solution, a closed-loop chemical mechanism for material degradation and regeneration has been achieved. The specific recycling mechanism is as follows: Decrosslinking reaction: Sodium borohydride, as a strong reducing agent, provides negative hydrogen ions that can break disulfide bonds in the network structure, reducing them to thiol functional groups. Macroscopically, this manifests as the disintegration of the three-dimensional crosslinked network, transforming it into a soluble linear polymer precursor solution, thus completing the degradation of waste polymers.

[0024] Re-crosslinking and recombination reaction: After introducing copper chloride into the system, divalent copper ions act as oxidants and catalytic sites, inducing free thiol groups in the solution to undergo oxidative dehydrogenation. The thiol groups then re-pair to form new dynamic disulfide bonds. The recovered powder, after being reshaped, undergoes a secondary photodimerization reaction triggered by ultraviolet light, restoring its original crosslinked network topology and shape memory mechanical properties, thus achieving the chemical recycling and reuse of polymer materials.

[0025] This invention provides a shape memory polymer based on a bottle brush-like structure and its preparation method. It has the following beneficial effects: 1. This invention utilizes polycaprolactone diol as the main chain and thiocyclopentyl groups at both ends provided by lipoic acid to crosslink under ultraviolet light, forming a covalent adaptive network rich in dynamic disulfide bonds. This network structure can undergo topological rearrangement under external stimuli, enabling the polymer to maintain the stability of conventional crosslinked networks while possessing deformation recovery and secondary processing capabilities, thus solving the problem that conventional permanently crosslinked polymers cannot be reshaped after molding.

[0026] 2. This invention, by adding an aqueous solution of sodium borohydride to waste polymers, enables the disulfide bonds at network nodes to break and be reduced to thiol groups, degrading the three-dimensional cross-linked network into a soluble linear precursor solution. Subsequently, by introducing copper chloride to catalyze the oxidative dehydrogenation reaction of the thiol groups, the disulfide bonds are re-paired and cross-linked. This dynamic exchange mechanism based on the redox of disulfide bonds allows the polymer powder to be collected, shaped, and restored to its original cross-linked topology.

[0027] 3. In this invention, a precursor solution is prepared using a good solvent and then directly cast into a film in a mold. Ultraviolet light irradiation is used to induce photo-ring-opening polymerization and dimerization reactions at the end groups. This crosslinking and curing process can be completed at room temperature without high-temperature heat treatment, thus avoiding the risk of local thermal degradation of the polycaprolactone backbone. At the same time, the solution casting combined with photocuring process facilitates the preparation of polymer devices with complex shapes. Attached Figure Description

[0028] Figure 1 This is the overall infrared spectrum of the sample in an embodiment of the present invention; Figure 2 This is a partial infrared spectrum of a sample from an embodiment of the present invention; Figure 3 This is a POM diagram of the crystallization process of PCL-TA CAN sample in an embodiment of the present invention; Figure 4 The following is a comparison of the basic mechanical properties and thermally driven self-healing efficiency of the present invention: (a) is a comparison of the test data of the initial tensile strength and the tensile strength after fracture, cutting and splicing repair of each sample; (b) is a distribution of the self-healing efficiency data of each sample calculated based on the tensile strength. Figure 5 The following is a comparison chart of the reconfigurable shape memory capability test of the present invention: (a) is a distribution chart of the shape fixation rate data of each sample in the thermomechanical cycle test, and (b) is a distribution chart of the shape recovery rate data of each sample in the thermomechanical cycle test. Figure 6 The figures show the results of the chemical closed-loop recycling and regeneration performance verification test of the present invention. (a) Mass recovery rate distribution of Example 2 under different chemical cycle generations, and (b) Evolution trend of tensile strength and elongation at break of samples of each regeneration generation in Example 2. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing polycaprolactone diol (PCL-OH) and polycaprolactone modified at both ends with lipoic acid (PCL-TA), including the following steps: (1) Under nitrogen protection, ε-caprolactone monomer, diethylene glycol and dibutyltin oxide were placed in a dry side-arm flask at a mass ratio of 400:11:1 and heated with magnetic stirring in an oil bath at 120°C for 5 hours. After the reaction was complete, the mixture was removed, cooled to room temperature, and the product was mixed with chloroform, a good solvent, and allowed to stand.

[0031] The precipitate was then added dropwise to the unsuitable solvent n-hexane using a dropper, stirred with a magnetic stirrer for 0.5 h, and then allowed to stand for 0.5 h to allow the product to precipitate. Finally, the precipitate was filtered and dried under vacuum at 40 °C to obtain a white powdery PCL-OH.

[0032] (2) Under nitrogen protection, the synthesized PCL-OH, thioctic acid (TA), 4-dimethylaminopyridine (DMAP), and N,N'-dicyclohexyl carbodiimide (DCC) were placed in a dry side-arm flask at a mass ratio of 1200:90:50:90. Chloroform, a good solvent, was then added, and the mixture was sonicated for 0.2 h to ensure uniform dissolution and mixing. The resulting solution turned bright yellow.

[0033] The flask was heated continuously in an oil bath at 15°C for 20 hours. After the reaction was complete, it was removed and cooled to room temperature. The byproduct precipitate dicyclohexylurea (DCU) was removed by filtration. The filtrate was added dropwise to the poor solvent n-hexane to precipitate the product. The mixture was stirred with a magnetic stirrer for 0.5 hours and then allowed to stand for 0.5 hours.

[0034] Finally, the precipitate was filtered and dried under vacuum at 40°C to obtain a light yellow powder product, namely polycaprolactone (PCL-TA) modified at both ends with thioctic acid.

[0035] Preparation Example 2: This preparation example provides a method for preparing polycaprolactone diol (PCL-OH) and polycaprolactone modified at both ends with lipoic acid (PCL-TA), including the following steps: (1) Under nitrogen protection, ε-caprolactone monomer, diethylene glycol and dibutyltin oxide were placed in a dry side-arm flask at a mass ratio of 400:13:2.5 and heated with magnetic stirring in an oil bath at 135°C for 7.5 h. After the reaction was complete, the mixture was removed, cooled to room temperature, and the product was mixed with dichloromethane, a good solvent, and allowed to stand.

[0036] The precipitate was then added dropwise to cyclohexane, a poor solvent, using a dropper. The mixture was stirred with a magnetic stirrer for 0.8 hours, and then allowed to stand for 0.8 hours to allow the product to precipitate. Finally, the precipitate was filtered and dried under vacuum at 45°C to obtain a white powdery PCL-OH.

[0037] (2) Under nitrogen protection, the synthesized PCL-OH, thioctic acid (TA), 4-dimethylaminopyridine (DMAP), and N,N'-dicyclohexylcarbodiimide (DCC) were placed in a dry side-arm flask at a mass ratio of 1250:105:65:105. Dichloromethane, a good solvent, was then added, and the mixture was ultrasonically vibrated for 0.6 h to ensure uniform dissolution and mixing. The resulting solution turned bright yellow.

[0038] The flask was heated in an oil bath at 25°C for 25 hours. After the reaction was complete, it was removed and cooled to room temperature. The byproduct precipitate dicyclohexylurea (DCU) was removed by filtration. The filtrate was added dropwise to the poor solvent cyclohexane to precipitate the product. The mixture was stirred with a magnetic stirrer for 0.8 hours and then allowed to stand for 0.8 hours.

[0039] Finally, the precipitate was filtered and dried under vacuum at 45°C to obtain a light yellow powder product, namely polycaprolactone (PCL-TA) modified at both ends with thioctic acid.

[0040] Preparation Example 3: This preparation example provides a method for preparing polycaprolactone diol (PCL-OH) and polycaprolactone modified at both ends with lipoic acid (PCL-TA), including the following steps: (1) Under nitrogen protection, ε-caprolactone monomer, diethylene glycol and dibutyltin oxide were placed in a dry side-arm flask at a mass ratio of 400:15:4 and heated with magnetic stirring in an oil bath at 150°C for 10 h. After the reaction was complete, the mixture was removed, cooled to room temperature, and the product was mixed with tetrahydrofuran, a good solvent, and allowed to stand.

[0041] The precipitate was then added dropwise to methanol, a poor solvent, using a dropper. The mixture was stirred with a magnetic stirrer for 1 hour, and then allowed to stand for 1 hour to allow the product to precipitate. Finally, the precipitate was filtered and dried under vacuum at 50°C to obtain a white powdery PCL-OH.

[0042] (2) Under nitrogen protection, the synthesized PCL-OH, lipoic acid (TA), 4-dimethylaminopyridine (DMAP), and N,N'-dicyclohexylcarbodiimide (DCC) were placed in a dry side-arm flask at a mass ratio of 1300:120:80:120. Tetrahydrofuran, a good solvent, was then added, and the mixture was ultrasonically vibrated for 1 hour to ensure uniform dissolution and mixing. The resulting solution turned bright yellow.

[0043] The flask was heated in an oil bath at 35°C for 30 hours. After the reaction was complete, it was removed and cooled to room temperature. The byproduct precipitate dicyclohexylurea (DCU) was removed by filtration. The filtrate was added dropwise to methanol, a poor solvent, to precipitate the product. The mixture was stirred with a magnetic stirrer for 1 hour and then allowed to stand for 1 hour.

[0044] Finally, the precipitate was filtered and dried under vacuum at 50°C to obtain a light yellow powder product, namely polycaprolactone (PCL-TA) modified at both ends with thioctic acid.

[0045] Examples 1-3: Example 1: This example provides a shape memory polymer based on a bottle brush structure and its preparation method, including the following steps: (1) Preparation of covalent adaptive network rich in dynamic disulfide bonds: The PCL-TA obtained in Preparation Example 1 was dissolved in chloroform, a good solvent, to prepare a solution with a concentration of 0.01 g / mL. Then, it was ultrasonically shaken for 0.2 h to make the solution uniformly mixed.

[0046] The polymer solution was poured into a polytetrafluoroethylene (PTFE) mold, and then the precursor film was irradiated with ultraviolet light for 0.5 h to induce photodimerization of the terminal thiocyclopentyl groups, thereby forming a dynamic cross-linked network.

[0047] The distance between the ultraviolet light source and the mold surface was fixed at 1.5 cm. After irradiation, a PCL-TA CAN film was obtained.

[0048] (2) Chemical recovery of covalent adaptive network: First, cut 0.5g of the covalent adaptive network film obtained in step (1) into fragments and immerse it in 10mL of good solvent chloroform to make it fully swollen. Add sodium borohydride aqueous solution (0.5g sodium borohydride dissolved in 0.5mL deionized water) to the swollen gel.

[0049] The mixture was stirred at room temperature until a homogeneous solution was formed, indicating that the disulfide crosslinks had been reduced and broken. Then, 0.2 g of copper chloride was dissolved in a 5:1 volume ratio of chloroform / deionized water and added dropwise to the degraded polymer solution to catalyze oxidation and dynamic exchange reactions. After the reaction was continued at room temperature for 20 h, the mixture was filtered to remove insoluble matter.

[0050] The filtrate containing recovered linear PCL-TA was added dropwise to a large volume of vigorously stirred n-hexane, a poor solvent, to induce precipitation. The precipitated polymer was collected by filtration, washed with ethanol, and dried under vacuum to finally recover PCL-TA powder.

[0051] (3) Crosslinking PCL-TA obtained by chemical recycling again: Dissolve the PCL-TA obtained by chemical recycling in step (2) in chloroform, a good solvent, to prepare a solution with a concentration of 0.01 g / mL, and then sonicate for 0.2 h to make the solution and mix evenly.

[0052] The polymer solution was poured into a PTFE mold, and the precursor film was then irradiated with ultraviolet light for 0.5 h. The distance between the ultraviolet light source and the mold surface was fixed at 1.5 cm. After irradiation, a regenerated PCL-TA CAN film was obtained.

[0053] Example 2: This example provides a shape memory polymer based on a bottle brush structure and its preparation method, including the following steps: (1) Preparation of covalent adaptive network rich in dynamic disulfide bonds: The PCL-TA obtained in Preparation Example 2 was dissolved in dichloromethane, a good solvent, to prepare a solution with a concentration of 0.05 g / mL. Then, it was ultrasonically vibrated for 0.6 h to make the solution uniformly mixed.

[0054] The polymer solution was poured into a PTFE mold, and then the precursor film was irradiated with ultraviolet light for 1 hour to induce photodimerization of the terminal thiocyclopentyl groups, thereby forming a dynamic cross-linked network.

[0055] The distance between the ultraviolet light source and the mold surface was fixed at 2.2 cm. After irradiation, a PCL-TA CAN film was obtained.

[0056] (2) Chemical recovery of covalent adaptive network: First, cut 0.75g of the covalent adaptive network film obtained in step (1) into fragments and immerse it in 17.5mL of good solvent dichloromethane to allow it to swell fully. Add sodium borohydride aqueous solution (0.75g sodium borohydride dissolved in 1.25mL deionized water) to the swollen gel.

[0057] The solution was stirred at room temperature until a homogeneous solution was formed. Then, 0.25 g of copper chloride was dissolved in a good solvent, dichloromethane / deionized water at a volume ratio of 7.5:2.5, and added dropwise to the degraded polymer solution to catalyze oxidation and dynamic exchange reactions. The reaction was continued at room temperature for 25 hours, after which the mixture was filtered to remove insoluble matter.

[0058] The filtrate containing recovered linear PCL-TA was added dropwise to the unsuitable solvent cyclohexane for precipitation. The precipitated polymer was collected by filtration, washed with ethanol, and dried under vacuum to finally recover PCL-TA powder.

[0059] (3) Crosslinking PCL-TA obtained by chemical recycling again: Dissolve the PCL-TA obtained by chemical recycling in step (2) in a good solvent dichloromethane to prepare a solution with a concentration of 0.05 g / mL, and then sonicate for 0.6 h to make the solution and mix evenly.

[0060] The polymer solution was poured into a PTFE mold, and the precursor film was then irradiated with ultraviolet light for 1 hour. The distance between the ultraviolet light source and the mold surface was kept constant at 2.2 cm. After irradiation, a regenerated PCL-TA CAN film was obtained.

[0061] Example 3: This example provides a shape memory polymer based on a bottle brush structure and its preparation method, including the following steps: (1) Preparation of covalent adaptive network rich in dynamic disulfide bonds: The PCL-TA obtained in Preparation Example 3 was dissolved in a good solvent tetrahydrofuran to prepare a solution with a concentration of 0.1 g / mL, and then ultrasonically vibrated for 1 h to make the solution uniformly mixed.

[0062] The polymer solution was poured into a custom-designed PTFE mold, and the precursor film was then irradiated with ultraviolet light for 1.5 hours to induce photodimerization of the terminal thiocyclopentyl groups. The distance between the ultraviolet light source and the mold surface was fixed at 3 cm. After irradiation, a PCL-TA CAN film was obtained.

[0063] (2) Chemical recovery of covalent adaptive network: First, cut 1g of the covalent adaptive network film obtained in step (1) into fragments and immerse it in 25mL of a good solvent, tetrahydrofuran, to allow it to swell fully. Add sodium borohydride aqueous solution (1g sodium borohydride dissolved in 2mL deionized water) to the swollen gel. Stir at room temperature until a homogeneous solution is formed.

[0064] Subsequently, 0.3 g of copper chloride was dissolved in a good solvent, tetrahydrofuran / deionized water, at a volume ratio of 10:5, and then added dropwise to the degraded polymer solution. The reaction was continued at room temperature for 30 h, after which the mixture was filtered to remove insoluble matter.

[0065] The filtrate containing recovered linear PCL-TA was added dropwise to methanol, a poor solvent, for precipitation. The precipitated polymer was collected by filtration, washed with ethanol, and dried under vacuum to finally recover PCL-TA powder.

[0066] (3) Crosslinking PCL-TA obtained by chemical recycling again: Dissolve the PCL-TA obtained by chemical recycling in step (2) in a good solvent tetrahydrofuran to prepare a solution with a concentration of 0.1 g / mL, and then sonicate for 1 h to make the solution and mix evenly.

[0067] The polymer solution was poured into a PTFE mold, and the precursor film was then irradiated with ultraviolet light for 1.5 hours. The distance between the ultraviolet light source and the mold surface was kept constant at 3 cm. After irradiation, a regenerated PCL-TA CAN film was obtained.

[0068] Comparative Examples 1-5: Comparative Example 1: The difference compared to Example 2 is as follows: In step (1), after the polymer solution is poured into the mold, it is not subjected to ultraviolet light irradiation treatment. The solvent is directly evaporated and cast into a film (i.e., an uncrosslinked linear PCL-TA film is obtained). The remaining steps are the same.

[0069] Comparative Example 2: The difference compared to Example 2 is as follows: The precursors are different. In the preparation of the precursor, the lipoic acid (TA) in Preparation Example 2 is replaced with an equimolar amount of a double bond modifier (such as acrylic acid). During film formation, a photoinitiator is added to perform irreversible crosslinking to form a thermosetting crosslinked PCL network. The remaining steps are the same.

[0070] Comparative Example 3: The difference compared to Example 2 is as follows: Without using the thioctic acid-modified PCL-TA precursor, without performing the ultraviolet light crosslinking step, the unmodified pure linear polycaprolactone (PCL-OH) synthesized in step (1) of Preparation Example 2 was directly dissolved and cast into a film, and the remaining steps were the same.

[0071] Comparative Example 4: The difference compared to Example 2 is as follows: In step (1), the ultraviolet irradiation time is changed to 0.2h, and the rest of the steps are the same.

[0072] Comparative Example 5: The difference compared to Example 2 is as follows: In step (1), the ultraviolet irradiation time is changed to 3 hours, and the rest of the steps are the same.

[0073] Test Examples 1-5: Test Example 1: Structural Characterization Test of Polymer Network Construction This test case verifies the end-group chemical modification structure using Fourier transform infrared spectroscopy and determines the formation of the cross-linked network using gel fractionation. The specific experimental steps are as follows: (1) Take the dried PCL-OH precursor powder and PCL-TA powder, and place them respectively on the detection crystal of a Fourier transform infrared spectrometer equipped with an attenuated total reflectance accessory. Adjust the pressure head to make the sample fit against the crystal. Set the spectral acquisition range to 4000 cm⁻¹. -1 Up to 400cm-1 The resolution is 4cm. -1 The infrared spectrum was collected by scanning 32 times. The resulting infrared spectrum is attached. Figure 1 and attached Figure 2 As shown, the attached Figure 1 The vertical axis, Intensity (au), represents light intensity. Figure 2 The vertical axis, Transmittance (au), represents transmittance, and the horizontal axis, Wavenumber (cm), represents transmittance. -1 ) represents the wave number.

[0074] (2) Cut thin film samples prepared in Examples 1-3 and Comparative Examples 1, 4, and 5 respectively, and weigh them. Record the initial mass as follows: (Approximately 0.2g). Place the membrane in a weighed 300-mesh stainless steel filter, seal it, and immerse it in a sealed glass bottle containing 50mL of dichloromethane. Extract at room temperature for 48 hours, changing the dichloromethane solvent every 12 hours to extract uncrosslinked free polymer chains.

[0075] (3) After extraction, remove the metal filter screen and dry it in a vacuum drying oven at 50℃ for 24 hours until constant weight. After cooling to room temperature, weigh the total mass, and subtract the mass of the filter screen to obtain the dry weight of the crosslinked network, which is recorded as . According to the formula, gel fraction = ( Calculate the gel content by multiplying the result by 100%. Test three parallel samples for each formulation and record the data.

[0076] Table 1. Gel fraction data of thin film samples under different preparation conditions

[0077] Based on the data in Table 1 and the appendix Figure 1 Appendix Figure 2 The infrared spectral characteristics confirmed that the prepolymer end groups were modified and a covalently cross-linked network was constructed. (Observation of attached...) Figure 1 It can be seen that PCL-OH at 3500cm -1 The area exhibits a hydroxyl absorption peak, which disappears in the PCL-TA spectrum after Steglich esterification, and a new peak appears at 1730 cm⁻¹. -1 An absorption peak corresponding to the carbonyl stretching vibration of the ester bond appears in the wavenumber domain. (See attached image.) Figure 2 It can be seen that in the low wavenumber region, the PCL-TA spectral line is at 640 cm⁻¹ -1 and 500cm -1The newly added absorption peaks at the positions are attributed to the CS bond stretching vibration and the characteristic vibration of the SS disulfide bond within the 1,2-dithiopentane ring, respectively. The changes in the spectral signal correspond to the coupling process between the lipoic acid molecule and the terminal hydroxyl group of polycaprolactone, indicating that the synthesis of the PCL-TA pre-crosslinker with the dynamic dithiopentane end group is consistent with the design.

[0078] The gel fraction test data reflects the effect of ultraviolet light irradiation on network construction. Comparative Example 1, without ultraviolet light irradiation, had a gel fraction of 0, indicating that the material contains physical entanglements of linear molecular chains, which dissolve upon contact with solvents. Comparative Example 4, with an irradiation time of 0.2 hours, had a gel fraction of 43.32%, indicating that the energy provided by the shorter exposure time was insufficient to induce sufficient cross-linking of the terminal groups, leaving free molecular chain segments in the system.

[0079] The gel fraction in Examples 1 to 3 increased from 82.17% to 95.76%, indicating that within 0.5 to 1.5 hours of irradiation, disulfide bonds underwent ring-opening coupling and bond exchange, resulting in the formation of a three-dimensional covalent network. When the irradiation time was extended to 3 hours (Comparative Example 5), the gel fraction dropped back to 88.91%. Excessive UV radiation triggered localized photo-oxidative degradation of the polymer backbone or excessive cross-linking side reactions, leading to a decrease in the integrity of the network structure. The reaction parameters selected in the examples can form an adaptive disulfide bond network and avoid matrix degradation.

[0080] Test Example 2: Test on the Evolution Mechanism of Internal Crystallographic Phases in Materials This test example uses differential scanning calorimetry to determine the thermodynamic phase transition data of the polymer network, combined with polarized light microscopy to observe the dynamic evolution of the material's crystal morphology. The specific experimental steps are as follows: (1) Cut 5 to 8 mg of sample from the films prepared in Examples 1 to 3 and Comparative Examples 1 and 2, place them in an aluminum crucible and seal it, and prepare an empty aluminum crucible as a reference end. Place the sample and the reference crucible in the heating furnace of the differential scanning calorimeter, and introduce high-purity nitrogen gas at a flow rate of 50 mL / min.

[0081] Set the temperature program: heat from room temperature to 100℃ at a rate of 10℃ / min, hold for 5 minutes; cool to -40℃ at a rate of 10℃ / min, and record the exothermic crystallization curve; hold for 5 minutes, then heat to 100℃ at a rate of 10℃ / min, and record the endothermic melting curve of the second heating. Extract the crystallization temperature, melting temperature, and enthalpy change values.

[0082] (2) A thin slice with a thickness of approximately 50 micrometers was cut from the film prepared in Example 2 and placed between a glass slide and a coverslip, below the objective lens of a polarizing microscope on a temperature-controlled hot and cold stage. The crossed polarizers were adjusted to eliminate the background light in the field of view. The stage temperature was set to increase from 25°C to 60°C at a rate of 5°C / min, and then decrease to 0°C at the same rate. The microscope CCD camera was turned on to record the changes in the birefringence pattern of the crystalline phase at regular intervals. The results of the polarizing microscope observations are attached. Figure 3 As shown in the figure, Heating indicates the heating process, Cooling indicates the cooling process, and the scale bar of each sub-figure is 100μm. Table 2. Thermodynamic phase transition data of polymer networks under different preparation conditions

[0083] Based on the data in Table 2 and the appendix Figure 3 In-situ polarized light microscopy observations revealed that the polycaprolactone covalent adaptive network exhibits temperature-dependent phase transition behavior, verifying the shape memory mechanism dominated by the crystalline phase. At room temperature (25℃), a bright refractive region was observed, indicating that the system was in a crystalline state. When the temperature rose to 30℃ and 50℃, the area of ​​the bright crystalline region decreased, and the birefringence weakened. At 60℃, the field of view became extinct, corresponding to the melting and transformation of the crystalline phase into an amorphous state. When the temperature decreased to the range of 40℃ to 20℃, crystal nuclei appeared and grew in the field of view, and at 0℃, the crystalline structure filled the entire field of view. This process is consistent with differential scanning calorimetry (DSC) data.

[0084] Thermodynamic data show that Comparative Example 1, lacking a chemically cross-linked network, exhibited unrestricted molecular chain movement, resulting in the highest crystallization temperature, melting temperature, and crystallinity among all groups. In Examples 1 to 3, as the cross-linking density of the covalent adaptive network increased, the polycaprolactone chains were confined within a three-dimensional disulfide bond network topology. Increased steric hindrance hindered the folding of chain segments into the lattice, leading to a decrease in crystallization temperature from 21.6°C to 17.5°C and a reduction in crystallinity from 32.4% to 27.6%. Even with cross-linking limiting some crystallization ability, the material maintained approximately 30% crystallinity at room temperature. The crystalline regions, stable at room temperature, acted as physical nodes.

[0085] When a material deforms and cools under external force, the molecular chain segments rearrange to form new crystalline regions, fixing the temporary shape. When reheated above the melting temperature, the crystalline regions melt and lose their restraining ability, the molecular chain segments regain their degrees of freedom, and the material recovers its shape through the entropic elastic restoring force driven by the disulfide bond network. Thermodynamic and microstructural data confirm that crystallization and melting phase transitions are the physical processes driving the shape memory behavior of this material.

[0086] Test Example 3: Comparison Test of Basic Mechanical Performance and Dynamic Self-Healing Performance This test example determines the uniaxial tensile properties of the material at room temperature and evaluates the degree of tensile strength recovery caused by the reorganization of the internal covalent network through cutting, splicing, and heat treatment processes. The specific experimental steps are as follows: (1) Cut dumbbell-shaped tensile specimens conforming to ISO 37-2 standard, and measure the width and thickness of the working section. The specimens are clamped in a universal testing machine with a gauge length of 20 mm. The tensile rate is set to 50 mm / min, and tensile tests are performed at room temperature. The tensile strength and elongation at break are extracted. The average value of 5 parallel specimens in each test group is taken.

[0087] (2) Prepare templates of the same size and cut them transversely at the center of the working section to form two cross sections. Fit the cross sections together and place them on a polytetrafluoroethylene plate coated with silicone oil. Apply a 10g weight above the joint to maintain contact pressure. Place the assembly in an 80℃ forced-air drying oven for 24 hours. Remove and cool for 12 hours.

[0088] Tensile tests were performed on the healed spliced ​​strips under the same conditions, and the tensile strength was recorded. The recovery percentage was calculated using the formula: Self-healing efficiency = (Tensile strength after repair / Initial tensile strength) × 100%.

[0089] Table 3. Initial mechanical properties and thermally driven self-healing efficiency data of different samples

[0090] Based on the data in Table 3 and Figure 4 The performance test comparison charts shown demonstrate that the introduction of the covalent cross-linked network and the setting of UV curing parameters have a regulatory effect on the basic mechanical properties and damage repair capabilities of the polycaprolactone substrate. Compared with the uncross-linked Comparative Example 1 and the pure polycaprolactone Comparative Example 3, the initial tensile strength of Example 2 increased to 18.67 MPa, while the elongation at break remained at 645.2%.

[0091] Test results show that the crosslinking reaction restricts macroscopic slip deformation under stress, improving the material's load transfer and stress dissipation capabilities. UV irradiation time deviating from the range of the examples led to performance degradation; in Comparative Example 4, insufficient crosslinking density resulted in a tensile strength of 12.04 MPa; in Comparative Example 5, excessive radiation caused localized polymer degradation and over-crosslinking, leading to material embrittlement and a drop in elongation at break to 198.5%. The parameter settings of the examples achieved a balance between tensile strength and toughness.

[0092] In the damage repair test at 80°C, the temperature exceeded the melting temperature of the polycaprolactone crystallization zone, and the polymer segments regained their diffusion ability. Comparative Example 2, employing an irreversible covalent network structure, had a self-healing efficiency of only 2.1%, losing its load-bearing capacity. Comparative Example 3, relying solely on physical diffusion and entanglement, achieved a repair efficiency of 36.5%. Example 2 achieved a repair efficiency of 88.27%.

[0093] Because its network structure contains dynamic disulfide bonds, the bond exchange reaction is activated upon temperature increase. Driven by heat, the molecular chains diffuse across physical gaps, and the disulfide crosslinking points break and couple at the contact surfaces. The synergistic effect of covalent bond reconstruction and chain segment diffusion eliminates physical gaps, causing the cross-sections to fuse into a crosslinked entity, restoring structural integrity.

[0094] Test Example 4: Comparative Test of Reconfigurable Shape Memory Capability This test case evaluates the material's shape retention rate and shape recovery rate, and verifies the effectiveness of the dynamic covalent network in reshaping the material's shape through a secondary thermal programming experiment. The specific experimental steps are as follows: (1) Using a die cutter, cut the films of Examples 1 to 3, Comparative Example 2 and Comparative Example 3 into rectangular strips 30 mm long and 5 mm wide. Mark two parallel lines 10 mm apart in the middle of the strip as the initial gauge length, and record this length as _____. Place the sample in a dynamic thermomechanical analyzer with a temperature-controlled ambient chamber or a constant-temperature hot stage with a scale.

[0095] (2) Raise the ambient temperature to 60℃ and maintain it for 10 minutes. After the spline reaches thermal equilibrium, apply uniaxial tensile stress to it, causing it to elongate to approximately 200% of the initial gauge length (i.e., the deformation is 100%). Record the gauge length at this point. Maintaining the tensile stress state, the ambient temperature was reduced to 0°C at a rate of 5°C / min and held at this temperature for 15 minutes. Subsequently, the external tensile stress was unloaded, and the sample was allowed to stand at room temperature (25°C) for 1 hour to allow the internal structure to relax and reach equilibrium. The gauge length after unloading was measured and recorded. According to the formula: Shape fixation rate = ( ) / ( ) × 100%, calculates the material's ability to hold a temporary shape.

[0096] (3) Place the unloaded specimen from step (2) onto a flat polytetrafluoroethylene plate and place it in a preheated oven at 60°C. Keep it at this temperature for 30 minutes without any external stress constraints. After removing the specimen and cooling it to room temperature, measure and record the final recovered gauge length. According to the formula: Shape recovery rate = ( ) / ( ) × 100%, calculates the material's ability to recover its initial shape.

[0097] (4) Take the initial flat rectangular sample before the test, spirally wind it around a glass rod with a diameter of 8 mm, and fix both ends with high-temperature resistant polyimide tape to maintain its spiral shape. Place the fixed component in a vacuum oven at 80°C for 2 hours.

[0098] After processing, remove the component and allow it to cool naturally at room temperature for 2 hours. Remove the fixing tape and observe whether the sample retains its spiral three-dimensional shape as a new permanent shape after unloading. If it does, record it as having reshaping ability; if the sample springs back to its original flat rectangle, record it as not having reshaping ability.

[0099] Table 4. Shape memory parameters and secondary thermal reshaping results for different materials

[0100] Based on the data in Table 4 and Figure 5 The comparison chart of shape memory capability tests shows that the crystalline phase state and covalent network topology affect shape memory and reconfigurability. Comparative Example 3 did not establish a covalent network; when heated above the melting temperature, the polymer chain segment slippage exhibited a viscous flow state, failing to maintain macroscopic continuity. Comparative Example 3 melted and flowed at the test temperature, and is marked as untestable.

[0101] Combination Figure 5 Data distributions (a) and (b) show that Examples 1 to 3 and Comparative Example 2 exhibit high shape fixation and shape recovery rates, ranging from 96% to 99%. At room temperature, the polycaprolactone segments are in a crystalline state, with microcrystalline regions acting as physical nodes to restrict conformational changes in the amorphous segments. After stretching and orientation cooling at 60°C, the newly formed crystalline network locks the strain conformation of the segments, resulting in shape fixation. When the crystalline regions melt upon heating, the physical constraints are released, and the chemically cross-linked network structure provides recovery force, driving the deformation to shrink back to its initial state.

[0102] In the secondary thermal programming and reshaping test at 80°C, Comparative Example 2 employed an irreversible cross-linked structure, with a fixed and unchangeable cross-linked network. Thermal deformation under external force induces elastic internal stress within the material; upon removal of the external force, the molecular chains spring back directly, failing to revert to a new spatial shape. The Example introduced a dynamic covalent network containing disulfide bonds. At 80°C, the disulfide bonds are activated, undergoing breakage and coupling reactions.

[0103] Polymer molecular chains undergo topological rearrangement through bond exchange, relaxing the internal stress accumulated by deformation. The cooling process solidifies the chain segment conformation, establishing new topological constraints in the material while retaining the secondary-defined helical shape. The combination of the physically reversible phase transformation of the crystalline phase and the chemical dynamic exchange of the disulfide covalent phase enables the material to change its permanent shape.

[0104] Test Example 5: Chemical Closed-Loop Recovery and Performance Regeneration Verification Test This test case evaluates the closed-loop recovery rate of the polymer network and measures the mechanical and shape memory properties of the film after regeneration. The specific experimental procedures are as follows: (1) Weigh 2.00 g of each of the film samples from Example 2 and Comparative Example 2. Place the samples in a glass bottle containing 100 mL of dichloromethane, and add 0.50 g of dithiothreitol and 0.20 mL of triethylamine. Stir magnetically (300 rpm) at room temperature for 24 hours. Vacuum filter the reaction mixture through a 0.22 μm polytetrafluoroethylene filter membrane. Collect the insoluble residue on the filter membrane, dry it in a vacuum drying oven, and weigh it.

[0105] (2) The filtrate was added dropwise to 500 mL of ice-cold n-hexane solvent to precipitate the polymer. The precipitate was collected and washed with anhydrous ethanol to remove residual reducing agent. It was then dried in a vacuum drying oven at 40 °C until constant weight, and the mass recovery rate was calculated by weighing.

[0106] (3) The dried polymer was reconstituted in dichloromethane to prepare a 15% (w / w) solution. The solution was poured into a polytetrafluoroethylene mold to evaporate the solvent at room temperature for 12 hours. The molded film was then irradiated under a 365 nm ultraviolet light source for 1 hour to obtain the first-generation recycled film.

[0107] (4) The recycled film was subjected to tensile and thermomechanical cycling tests under the test conditions of test examples 3 and 4. The tensile strength, elongation at break and shape recovery rate were recorded. After completion, the film fragments were put back into the reduction and degradation system of step (1) and the above process was repeated to complete the second and third generation recycled film tests.

[0108] Table 5. Recovery and regeneration performance data of different samples in the chemical depolymerization cycle

[0109] Note: "-" in Table 5 indicates that the sample has not undergone a recycling step or cannot be tested for the corresponding parameters because it cannot be depolymerized and regenerated.

[0110] Based on the data in Table 5 and Figure 6 The diagram shows the chemical closed-loop recovery and regeneration performance test results. The disulfide bond structure design affects the chemical degradation and closed-loop regeneration performance of the polycaprolactone substrate. Comparative Example 2 is formed by irreversible carbon-carbon double bond crosslinking. It did not dissolve after treatment in a dichloromethane solution containing dithiothreitol, and the filter membrane retained insoluble residue, with a mass recovery rate of 0%.

[0111] The nodes of the irreversible covalent network cannot break, and the topology remains rigid. Comparative Example 2 failed to obtain the recycled prepolymer and was not successfully developed. Figure 6 The sample from Example 2 was dissolved in the same system. Dithiothreitol reduced and cleaved the crosslinked nodes in the network into terminal thiol groups via a thiol-disulfide bond exchange reaction. The crosslinked topology disintegrated, and the three-dimensional network was transformed into soluble prepolymer molecular chains, such as... Figure 6 As shown in (a), the first-generation recycling mass recovery rate was 94.1%.

[0112] During the remodeling phase, the free thiol groups of the prepolymer undergo oxidative coupling reactions to regenerate disulfide bonds and reconstruct the network. Figure 6 As shown in (b) and (c), the tensile strength of the first-generation recycled film was 17.52 MPa, and the shape recovery rate was 96.35%. Mechanical testing revealed that the recombination of the cross-linked network restored the material's load-bearing capacity and shape memory internal stress mechanism. With the increase in the number of cycles to the third generation, the mass recovery rate decreased to 84.2%, the tensile strength decreased to 14.16 MPa, and the elongation at break decreased to 511.7%. Repeated dissolution and precipitation led to the physical loss of oligomer components, and ultraviolet radiation caused local photo-oxidative degradation of the polymer backbone, resulting in parameter decay. After three reconstructions, the shape recovery rate of the third-generation recycled film remained at 91.04%. The cleavage and recombination process of disulfide bonds provided a chemical recovery and structural regeneration pathway for cross-linked polymers.

Claims

1. A shape memory polymer based on a bottle brush-like structure, characterized in that, The polymer is a covalent adaptive network cross-linked structure rich in dynamic disulfide bonds. The polymer is prepared by dissolving a polycaprolactone precursor with both ends modified by thioctic acid in a good solvent to form a polymer solution, and then inducing the photodimerization reaction of the thiohexacyclopentyl groups at the end of the polymer chain to undergo cross-linking polymerization in a mold by ultraviolet light irradiation, thus completing the spatial structure construction of the covalent adaptive network. The polycaprolactone precursor modified with lipoic acid at both ends is prepared by chemical reaction of polycaprolactone diol, lipoic acid, 4-dimethylaminopyridine and N,N'-dicyclohexylcarbodiimide in a mass ratio of 1200-1300:90-120:50-80:90-120, wherein lipoic acid modifies both ends of the polycaprolactone diol and provides terminal thiohexecyclopentyl groups; The polycaprolactone diol is prepared by mixing ε-caprolactone monomer, diethylene glycol and dibutyltin oxide in a mass ratio of 400:11-15:1-4 and reacting them under oil bath heating conditions. The good solvent is selected from chloroform, dichloromethane or tetrahydrofuran.

2. The shape memory polymer based on a bottle brush-like structure according to claim 1, characterized in that, The mass ratio of polycaprolactone diol, thioctic acid, 4-dimethylaminopyridine, and N,N'-dicyclohexylcarbodiimide is 1250:105:65:

105.

3. The shape memory polymer based on a bottle brush-like structure according to claim 1, characterized in that, The mass ratio of the ε-caprolactone monomer, diethylene glycol, and dibutyltin oxide is 400:13:2.

5.

4. The shape memory polymer based on a bottle brush-like structure according to claim 1, characterized in that, The preparation process of the polycaprolactone precursor modified with thioctic acid at both ends is as follows: the polycaprolactone diol, thioctic acid, 4-dimethylaminopyridine and N,N'-dicyclohexylcarbodiimide are placed in a flask, the good solvent is added and ultrasonically vibrated to dissolve and mix evenly, and then heated in an oil bath environment at 15-35°C for 20-30 hours. After filtering to remove the generated by-product precipitate, the filtrate is dropped into a poor solvent selected from n-hexane, cyclohexane or methanol to precipitate. The precipitate is filtered and dried under vacuum to obtain the product.

5. The shape memory polymer based on a bottle brush-like structure according to claim 1, characterized in that, The preparation process of the polycaprolactone diol is as follows: under nitrogen protection, the ε-caprolactone monomer, diethylene glycol and dibutyltin oxide are placed in a flask and continuously stirred and heated in an oil bath at 120-150°C for 5-10 hours. After cooling, it is mixed with the good solvent, and then dropped into a poor solvent selected from n-hexane, cyclohexane or methanol to precipitate and stand. The precipitate is then filtered and dried under vacuum to obtain the product.

6. A method for preparing a shape memory polymer based on a bottle brush-like structure, characterized in that, The preparation of a shape memory polymer based on a bottle brush structure according to any one of claims 1 to 5 comprises the following steps: A polycaprolactone precursor modified with thioctic acid at both ends was dissolved in a good solvent to prepare a precursor polymer solution. The precursor polymer solution is subjected to ultrasonic vibration to dissolve and mix it evenly; The homogeneous precursor polymer solution is poured into a mold to form a precursor film. The precursor film is then irradiated with ultraviolet light to induce photodimerization of the terminal thiocyclopentyl groups, thereby forming a crosslinked network containing dynamic disulfide bonds. After irradiation, the shape memory polymer based on the bottle brush structure is obtained.

7. The preparation method according to claim 6, characterized in that, The concentration of the precursor polymer solution is 0.01–0.1 g / mL, and the ultrasonic oscillation time is 0.2–1 h.

8. The preparation method according to claim 6, characterized in that, When the ultraviolet light is applied, the distance between the ultraviolet light source and the mold surface is fixed at 1.5 to 3 cm, and the ultraviolet light irradiation time is 0.5 to 1.5 h.

9. The preparation method according to claim 6, characterized in that, The process includes a chemical recovery process for covalently adaptive networks, in which the obtained polymer is shredded and immersed in a good solvent to allow it to swell fully; Add sodium borohydride aqueous solution to the swollen gel and stir at room temperature until a homogeneous polymer solution after degradation is formed; Subsequently, a mixture of a good solvent containing copper chloride and deionized water was added dropwise to the homogeneous polymer solution after degradation to catalyze oxidation and dynamic exchange reactions. Filter the mixture to remove insoluble matter; The filtrate containing the recovered material is dripped into a poor solvent to precipitate. The polymer obtained from the precipitation is collected by filtration, washed, and then vacuum dried to recover the powder.

10. The preparation method according to claim 9, characterized in that, The catalytic oxidation and dynamic exchange reaction is carried out at room temperature for 20-30 hours, and the undesirable solvent is selected from n-hexane, cyclohexane or methanol; The recovered powder was redissolved in a good solvent to prepare a solution, which was then subjected to ultrasonic vibration and ultraviolet light irradiation to obtain the regenerated polymer.

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