Temperature-responsive polycaprolactone shape memory material and preparation method thereof

Abstract

The application provides a temperature-controllable polycaprolactone shape memory material and a preparation method thereof, and the method comprises the following steps: polycaprolactone-poly(2-vinyl) ethylene glycol copolymer and a polythiol compound are cross-linked to form a cross-linked material under the action of a photoinitiator through UV light curing, so that the temperature-controllable polycaprolactone shape memory material is obtained; the cross-linking density of the cross-linked material is adjusted by adjusting the vinyl content, the molecular weight and the structure of the polycaprolactone-poly(2-vinyl) ethylene glycol copolymer, so that the response temperature of the shape memory material is adjusted, and the shape memory performance, the mechanical strength, the toughness and the thermal stability of the shape memory polymer material are improved.

Description

Technical Field

[0001] This invention relates to the field of radiation-cured materials technology, specifically to a polycaprolactone shape memory material with adjustable response temperature and its preparation method. Background Technology

[0002] Shape memory polymers (SMPs), as a class of stimulus-responsive materials, have attracted widespread attention due to their potential applications in artificial intelligence, aerospace, biomedical devices, smart textiles, electronic devices, and sensors. Among various stimulus-responsive polymers, temperature-responsive SMPs exhibit permanent shape at high temperatures, but deform under constant external force at the response temperature (Angew. Chem. Int. Ed. 2002, 41, 2034-2057; Adv. Mater. 2010, 22, 3388-3410; Prog. Polym. Sci. 2015, 49-50, 3-33; Adv. Mater. 2021, 33, 2170210). Polycaprolactone (PCL) is an attractive candidate material for SMPs in biomedical applications due to its biodegradability, biocompatibility, and elasticity. Constructing cross-linked networks is another way to prepare PCL SMPs, which can effectively improve the thermal stability and shape recovery rate of the material (Macromol. Rapid Commun. 2011, 32, 1264-1269.).

[0003] A common method for crosslinking PCL is to introduce crosslinkable end groups into the PCL precursor. Examples include dimethacrylate, methacrylate, and mercapto groups (Polym. Sci. A Polym. Chem., 2005, 43: 1369-1381; Polym. Chem., 2012, 3, 2956-2963; Macromolecules 2014, 47, 1828-1836). However, current strategies can only introduce one crosslinkable group (such as acrylate and allyl) at the end of the PCL, causing the mechanical properties and shape memory properties of the material to depend on the molecular weight of the prepolymer. By photo-clicking thiols, PCL containing allyl end groups was photocrosslinked with tetrafunctional thiols to prepare PCL networks, whose mechanical properties were significantly better than those of similar materials crosslinked with acrylates (Adv. Mater. 2023, 35, 2210136). While crosslinking density can be increased through crosslinking reactions between multi-arm PCL precursors and / or multifunctional curing agents (such as thiols), crosslinked networks formed by PCLs with low crosslinkable group content may limit further increases in entropic elasticity, thus affecting the shape memory and recovery capabilities of SMPs. Therefore, developing PCL precursors with multiple crosslinking sites and constructing controllable crosslinked networks to tune shape recovery temperatures as well as thermal and mechanical properties is highly attractive. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a polycaprolactone shape memory material with adjustable response temperature and a method for its preparation.

[0005] To address the challenges posed by shape memory polymers (SMPs) in practical applications, such as poor shape recovery, low mechanical strength, poor post-cycling recovery, and unsatisfactory thermal stability, this invention introduces a series of poly(2-vinyl)ethylene glycol units at the ends of polycaprolactone polyol through an allyl etherification strategy, forming a polycaprolactone-poly(2-vinyl)ethylene glycol copolymer, thereby successfully constructing a shape memory material with a controllable crosslinked network structure. This strategy aims to improve the shape memory performance, mechanical strength, toughness, and thermal stability of shape memory polymer materials to meet the application requirements of SMPs in high-strength and complex environments.

[0006] According to one aspect of the present invention, a method for preparing a polycaprolactone shape memory material with adjustable response temperature is provided, comprising: a polycaprolactone-poly(2-vinyl)ethylene glycol copolymer and a polythiol compound are subjected to a photoinitiator and then cured by UV light to form a crosslinked material, thereby obtaining a polycaprolactone shape memory material with adjustable response temperature.

[0007] By adjusting the vinyl content, molecular weight, and structure of the prepolymer (i.e., polycaprolactone-poly(2-vinyl)ethylene glycol copolymer), the crosslinking density of the crosslinking material can be adjusted, thereby regulating the response temperature of the shape memory material and improving the shape memory performance, mechanical strength, toughness, and thermal stability of SMPs.

[0008] Specifically, the higher vinyl content in polycaprolactone-poly(2-vinyl)ethylene glycol copolymers provides more crosslinking sites. Furthermore, the lower molecular weight and shorter chain segments make it easier for the terminal vinyl glycol units to form crosslinking points with thiols. This increase in crosslinking points leads to a higher crosslinking density, which in turn reduces the material's crystallinity and causes a decrease in melting temperature.

[0009] Optionally, the polycaprolactone-poly(2-vinyl)ethylene glycol copolymer has the structure shown in the following general formula:

[0010]

[0011]

[0012] R1 is selected from hydrogen, C1-C 20 Alkyl, benzyl, C6-C 14 Aryl, C6-C 14 Oxyheterocycles, C6-C 14 Nitrogen heterocycles, C6-C 14 Sulfur heterocycles, C5-C 20 oxygen heterochain, C5-C 20 Nitrogen heterochains and C5-C 20 Any of the sulfur heterochains;

[0013] R2, R3, and R4 are selected from C1-C1. 20 Alkyl, benzyl, C6-C 14 Aryl, C6-C 14 Oxyheterocycles, C6-C 14 Nitrogen heterocycles, C6-C 14 Sulfur heterocycles, C5-C 20 oxygen heterochain, C5-C 20 Nitrogen heterochains and C5-C 20 Any of the sulfur heterochains;

[0014] m, m1, m2, m3, m4, n, n1, n2, n3, and n4 are all positive integers, and m, m1, m2, m3, m4, n, n1, n2, n3, and n4 ≥ 1.

[0015] Optionally, the polycaprolactone-poly(2-vinyl)ethylene glycol copolymer has the structures shown in Formulas 2 and 4, wherein R2 and R4 are selected from C1-C4. 20 Alkyl, benzyl, C6-C14 Aryl, C6-C 14 Oxyheterocycles, C6-C 14 Nitrogen heterocycles, C6-C 14 Sulfur heterocycles, C5-C 20 oxygen heterochain, C5-C 20 Nitrogen heterochains and C5-C 20 Any of the sulfur heterochains;

[0016] m, m1, m2, m3, m4, n, n1, n2, n3, and n4 are all positive integers, and m, m1, m2, m3, m4, n, n1, n2, n3, and n4 ≥ 1.

[0017] The vinyl content of the aforementioned polycaprolactone-poly(2-vinyl)ethylene glycol copolymer can be flexibly adjusted by modifying the molecular structure, allowing for controllable control over crosslinking density and material functionality. The vinyl groups of the copolymer form a crosslinked network structure through thiol-ene reactions or free radical reactions, which can significantly improve mechanical properties, dimensional stability, and thermal properties. Shape memory materials obtained using this copolymer exhibit enhanced thermal stability, which is beneficial for optimizing mechanical properties and demonstrates good functionalization potential. Using copolymers with other structures may result in insufficient functional groups, monocrystalline structure, and poor crosslinking density.

[0018] Optionally, the polycaprolactone-poly(2-vinyl)ethylene glycol copolymer has the structures shown in Formulas 2 and 4, wherein:

[0019] R2 is

[0020] R4 is

[0021] The aforementioned copolymers can improve the mechanical properties and fatigue resistance of shape memory materials, and shape memory materials have higher thermal stability, thereby enhancing shape memory performance and increasing their functionalization.

[0022] Optionally, the polycaprolactone-poly(2-vinyl)ethylene glycol copolymer has a number-average molecular weight of 500–100,000 and a double bond content of 0.10–6.40 mmol / g. A higher vinyl content provides more crosslinking sites. Furthermore, a lower molecular weight and shorter molecular chain segments make it easier for the terminal vinyl glycol units to form crosslinking points with thiols. This increase in crosslinking points leads to a higher crosslinking density, thereby reducing the material's crystallinity and causing a decrease in melting temperature.

[0023] Optionally, the polythiol compound is any one of pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP), trimethylolpropane tris(3-mercaptopropionic acid) (TMPTMP), and 1,4-butanediol bis(mercaptoacetate) (BDBA).

[0024] The aforementioned polythiol compounds are determined based on the number and distribution of functional groups, chemical activity, solubility and compatibility, and post-curing properties, resulting in materials with adjustable mechanical properties and advantages such as rapid curing, high transparency, and uniformity. Using polythiol compounds with other structures may lead to functionality mismatch, insufficient reaction rate, solubility issues, and potentially side reactions.

[0025] Optionally, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0026] The main considerations for photoinitiators include absorption spectrum matching, initiation efficiency, solubility, stability and byproducts, toxicity and safety, and required curing depth. Using 2-hydroxy-2-methyl-1-phenyl-1-propanone as a photoinitiator enables rapid curing (Irgacure 1173 generates sufficient free radicals in a short time, significantly shortening curing time and improving production efficiency) and uniform curing (its high light absorption efficiency and solubility ensure uniform curing reaction, avoiding incomplete curing or surface oxygen inhibition). Using other substances as photoinitiators may result in unreliable absorption spectra, byproduct effects, and compatibility issues.

[0027] Optionally, the amounts of each component in the method are as follows: 80-93 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer, 5-15 parts of polythiol compound, and 2-5 parts of photoinitiator. The ratio of vinyl to thiol is 1:1, and the proportion of photoinitiator is 2% of the total mass, thereby allowing the thiol-olefin to form a cross-linked network.

[0028] Optionally, the process of forming crosslinked materials by UV light curing includes reacting under UV irradiation for 1-100 minutes. The reaction time takes into account factors such as light source intensity and wavelength, initiator concentration, reactivity of monomers and crosslinking agents, light penetration depth, temperature effects, and oxygen inhibition effects, in order to achieve rapid curing (seconds or minutes) and uniform curing to meet the needs of high-efficiency production.

[0029] According to another aspect of the present invention, a polycaprolactone shape memory material with adjustable response temperature is provided, which is prepared using the above-described preparation method. This shape memory material can be used in fields such as smart response materials and biomedical materials.

[0030] This invention can adjust the crosslinking density of polycaprolactone shape memory material by adjusting the vinyl content, molecular weight and structure in the prepolymer, thereby adjusting its response temperature, shape memory performance and mechanical properties. Sufficient crosslinking density can ensure that the shape memory material has good shape recovery ability, while exhibiting excellent mechanical properties, shape memory function and thermal stability.

[0031] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0032] This invention utilizes a curing system composed of a polycaprolactone-poly(2-vinyl)ethylene glycol copolymer and a polyfunctional thiol compound to obtain a polycaprolactone shape memory material with adjustable response temperature. This improves upon the low shape recovery rate and low cycle recovery rate of polycaprolactone shape memory materials. Furthermore, this invention grafts multiple (2-vinyl)ethylene glycol units onto the ends of the polycaprolactone. The more grafts there are, the higher the vinyl content in the copolymer. The higher functional structure enables the realization of a polymer network with a higher crosslinking density, resulting in excellent shape recovery rate, cycle recovery rate, and thermal stability when applied to shape memory materials. Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0034] Example 1

[0035] First, polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P1 is prepared, including the following steps:

[0036] 1,4-Butanediol (90.1 mg, 1 mmol, 1 eq.), ε-caprolactone (9214.8 mg, 80 mmol, 80 eq.), and stannous octoate (46.1 mg, 0.11 mmol, 0.5 wt% ε-caprolactone) were added to a dry reaction flask equipped with a magnetic stirrer. The flask was sealed with a rubber diaphragm, then evacuated and backfilled with nitrogen (this process was repeated three times). Ultra-dry toluene (20 mL) was added via syringe, and the reaction was carried out at 100 °C for 24 hours. 1 H-NMR was used to verify whether CL was completely converted.

[0037] After complete conversion of CL, PCL was grafted with ethylene ethylene carbonate (VEC). The reaction was cooled to 25°C, and the catalyst Pd2(dba)3·CHCl3 (15.6 mg, 0.15 mol% for VEC) and ligand DPEphos (16.1 mg, 0.3 mol% for VEC) were added to the reaction flask. The flask was then sealed with a rubber diaphragm, evacuated, and backfilled with nitrogen (this process was repeated three times). BEt3 (30 μL of 1 mol·L⁻¹) was added via syringe. -1 In THF solution (0.3 mol% for VEC) and VEC (1141.0 mg, 10 mmol, 10 eq.), the resulting mixture was stirred at 10 °C for 12 h. The catalyst was removed by rapid column chromatography, followed by rotary evaporation under vacuum to remove the solvent, then precipitation in cold petroleum ether, filtration and drying to give polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P1 (9508.1 mg, 95% yield, white solid).

[0038] GPC measured the molecular weight (Mn) of P1 to be 9800. 1 The vinyl content was determined to be 0.43 ± 0.02 mmol / g by ¹H NMR using the internal standard method (dimethyl terephthalate as the internal standard).

[0039] By weight, 93 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P1, 5 parts of BDBA, and 2 parts of Irgacure 1173 were melt-blended in a dark room at 80°C. After the mixture was homogeneous, it was poured into a mold and irradiated under 365nm ultraviolet light for 3 minutes to obtain a photocurable material.

[0040] Example 2

[0041] First, polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P2 is prepared, including the following steps:

[0042] 1,4-Butanediol (90.1 mg, 1 mmol, 1 eq.), ε-caprolactone (9214.8 mg, 80 mmol, 80 eq.), and stannous octoate (46.1 mg, 0.11 mmol, 0.5 wt% ε-caprolactone) were added to a dry reaction flask equipped with a magnetic stirrer. The flask was sealed with a rubber diaphragm, then evacuated and backfilled with nitrogen (this process was repeated three times). Ultra-dry toluene (20 mL) was added via syringe, and the reaction was carried out at 100 °C for 24 hours. 1 H-NMR was used to verify whether CL was completely converted.

[0043] After complete conversion of CL, PCL was grafted with ethylene ethylene carbonate (VEC). The reaction was cooled to 25°C, and the catalyst Pd2(dba)3·CHCl3 (31.2 mg, 0.15 mol% for VEC) and ligand DPEphos (32.2 mg, 0.3 mol% for VEC) were added to the reaction flask. The flask was then sealed with a rubber diaphragm, evacuated, and backfilled with nitrogen (this process was repeated three times). BEt3 (60 μL of 1 mol·L⁻¹) was added via syringe. -1 In THF solution, 0.3 mol% for VEC and VEC (2282.0 mg, 20 mmol, 20 eq.) were added, and the resulting mixture was stirred at 10 °C for 12 h. The catalyst was removed by rapid column chromatography, followed by rotary evaporation under vacuum to remove the solvent, and then precipitation was carried out in cold petroleum ether. The precipitate was filtered and dried to give polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P2 (9958.9 mg, 93% yield, white solid).

[0044] GPC measured the molecular weight (Mn) of P2 to be 10500. 1 The vinyl content was determined to be 1.04 ± 0.03 mmol / g by ¹H NMR using the internal standard method (dimethyl terephthalate as the internal standard).

[0045] By weight, 87 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P2, 11 parts of BDBA, and 2 parts of Irgacure 1173 were melt-blended in a dark room at 80°C. After the mixture was homogeneous, it was poured into a mold and irradiated under 365nm ultraviolet light for 3 minutes to obtain a photocurable material.

[0046] Example 3

[0047] First, polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P3 is prepared, including the following steps:

[0048] 1,4-Butanediol (90.1 mg, 1 mmol, 1 eq.), ε-caprolactone (9214.8 mg, 80 mmol, 80 eq.), and stannous octoate (46.1 mg, 0.11 mmol, 0.5 wt% ε-caprolactone) were added to a dry reaction flask equipped with a magnetic stirrer. The flask was sealed with a rubber diaphragm, then evacuated and backfilled with nitrogen (this process was repeated three times). Ultra-dry toluene (20 mL) was added via syringe, and the reaction was carried out at 100 °C for 24 hours. 1 H-NMR was used to verify whether CL was completely converted.

[0049] After complete conversion of CL, PCL was grafted with ethylene ethylene carbonate (VEC). The reaction was cooled to 25°C, and the catalyst Pd2(dba)3·CHCl3 (62.4 mg, 0.15 mol% for VEC) and ligand DPEphos (64.4 mg, 0.3 mol% for VEC) were added to the reaction flask. The flask was then sealed with a rubber diaphragm, evacuated, and backfilled with nitrogen (this process was repeated three times). BEt3 (120 μL of 1 mol·L⁻¹) was added via syringe. -1 In THF solution, 0.3 mol% for VEC and VEC (4564.0 mg, 40 mmol, 40 eq.) were added, and the resulting mixture was stirred at 10 °C for 12 h. The catalyst was removed by rapid column chromatography, followed by rotary evaporation under vacuum to remove the solvent, and then precipitation was carried out in cold petroleum ether. The precipitate was filtered and dried to give polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P3 (10902.1 mg, 90% yield, white solid).

[0050] GPC determined the molecular weight (Mn) of P3 to be 11200, and the vinyl content was determined to be 1.52 ± 0.06 mmol / g using the internal standard method (dimethyl terephthalate as the internal standard).

[0051] By weight, 83 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P3, 15 parts of BDBA, and 2 parts of Irgacure 1173 were melt-blended at 80°C in a dark room. After the mixture was homogeneous, it was poured into a mold and irradiated under 365nm ultraviolet light for 3 minutes to obtain a photocurable material.

[0052] Example 4

[0053] By weight, 82 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P3, 16 parts of TMPTMP, and 2 parts of Irgacure 1173 were melt-blended at 80°C in a dark room. After the mixture was homogeneous, it was poured into a mold and irradiated under 365nm ultraviolet light for 3 minutes to obtain a photocurable material.

[0054] Example 5

[0055] By weight, 83 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P3, 15 parts of PETMP, and 2 parts of Irgacure 1173 were melt-blended at 80°C in a dark room. After the mixture was homogeneous, it was poured into a mold and irradiated under 365nm ultraviolet light for 3 minutes to obtain a photocurable material.

[0056] Example 6

[0057] First, polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P4 is prepared, including the following steps:

[0058] Pentaerythritol (136.1 mg, 1 mmol, 1 eq.), ε-caprolactone (9214.8 mg, 80 mmol, 80 eq.), and stannous octoate (46.1 mg, 0.11 mmol, 0.5 wt% ε-caprolactone) were added to a dry reaction flask equipped with a magnetic stirrer. The flask was sealed with a rubber diaphragm, then evacuated and backfilled with nitrogen (this process was repeated three times). Ultra-dry toluene (20 mL) was added via syringe, and the reaction was carried out at 100 °C for 24 hours. 1 H-NMR was used to verify whether CL was completely converted.

[0059] After complete conversion of CL, PCL was grafted with ethylene ethylene carbonate (VEC). The reaction was cooled to 25°C, and the catalyst Pd2(dba)3·CHCl3 (31.2 mg, 0.15 mol% for VEC) and ligand DPEphos (32.2 mg, 0.3 mol% for VEC) were added to the reaction flask. The flask was then sealed with a rubber diaphragm, evacuated, and backfilled with nitrogen (this process was repeated three times). BEt3 (60 μL of 1 mol·L⁻¹) was added via syringe. -1 In THF solution, 0.3 mol% for VEC and VEC (2282.0 mg, 20 mmol, 20 eq.) were added, and the resulting mixture was stirred at 10 °C for 12 h. The catalyst was removed by rapid column chromatography, followed by rotary evaporation under vacuum to remove the solvent, and then precipitation was carried out in cold petroleum ether. The precipitate was filtered and dried to give polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P4 (9355.5 mg, yield 87%, white solid).

[0060] GPC determined the molecular weight (Mn) of P4 to be 10700, and the vinyl content was determined to be 1.16 ± 0.05 mmol / g using the internal standard method (dimethyl terephthalate as the internal standard).

[0061] By weight, 86 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P4, 12 parts of BDBA, and 2 parts of Irgacure 1173 were melt-blended in a dark room at 80°C. After the mixture was homogeneous, it was poured into a mold and irradiated under 365nm ultraviolet light for 3 minutes to obtain a photocurable material.

[0062] Example 7

[0063] First, polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P5 is prepared, including the following steps:

[0064] Triethylhydroxymethane (120.2 mg, 1 mmol, 1 eq.), ε-caprolactone (9214.8 mg, 80 mmol, 80 eq.), and stannous octoate (46.1 mg, 0.11 mmol, 0.5 wt% ε-caprolactone) were added to a dry reaction flask equipped with a magnetic stirrer. The flask was sealed with a rubber diaphragm, then evacuated and backfilled with nitrogen (this process was repeated three times). Ultra-dry toluene (20 mL) was added via syringe, and the reaction was carried out at 100 °C for 24 hours. 1 H-NMR was used to verify whether CL was completely converted.

[0065] After complete conversion of CL, PCL was grafted with ethylene ethylene carbonate (VEC). The reaction was cooled to 25°C, and the catalyst Pd2(dba)3·CHCl3 (31.2 mg, 0.15 mol% for VEC) and ligand DPEphos (32.2 mg, 0.3 mol% for VEC) were added to the reaction flask. The flask was then sealed with a rubber diaphragm, evacuated, and backfilled with nitrogen (this process was repeated three times). BEt3 (60 μL of 1 mol·L⁻¹) was added via syringe. -1 In THF solution, 0.3 mol% for VEC and VEC (2282.0 mg, 20 mmol, 20 eq.) were added, and the resulting mixture was stirred at 10 °C for 12 h. The catalyst was removed by rapid column chromatography, followed by rotary evaporation under vacuum to remove the solvent, and then precipitation was carried out in cold petroleum ether. The precipitate was filtered and dried to give polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P5 (9446.6 mg, 88% yield, white solid).

[0066] GPC determined the molecular weight (Mn) of P5 to be 10600, and the vinyl content was determined to be 1.10 ± 0.05 mmol / g using the internal standard method (dimethyl terephthalate as the internal standard).

[0067] By weight, 87 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer P5, 11 parts of BDBA, and 2 parts of Irgacure 1173 were melt-blended in a dark room at 80°C. After the mixture was homogeneous, it was poured into a mold and irradiated under 365nm ultraviolet light for 3 minutes to obtain a photocurable material.

[0068] Shape memory material performance testing

[0069] The application performance of the polycaprolactone shape memory material with adjustable response temperature in the above embodiments of the present invention was evaluated by formulating a curing material composition, including shape memory material properties, Young's modulus, mechanical properties, and thermal stability.

[0070] In each embodiment, the raw materials of each component were mixed evenly in a dark room according to the formulation shown in Table 1 to obtain a light-cured composition. Unless otherwise stated, all parts shown are by weight.

[0071] Table 1 Formulations of the photocurable compositions in each embodiment

[0072]

[0073]

[0074] The sample performance testing procedure is as follows:

[0075] (1) Tensile test: The cured materials obtained in Examples 1-7 were subjected to tensile test using a DMA850 dynamic thermomechanical analyzer. The tensile test was performed at a speed of 5 mm / min, and the accurate values ​​of modulus, tensile strength and elongation at break were obtained by the average value of five experiments.

[0076] (2) Thermal performance testing: A Netzsch thermogravimetric analyzer (TG 209F3) was used to test the thermal performance in the range of 50–700℃ at a heating rate of 20℃·min. -1 The thermal stability of the cured material under a nitrogen atmosphere was determined, and the temperature at which 5% mass degradation occurred was taken as the initial decomposition temperature (T). 5％ ).

[0077] (3) Thermal Response Temperature Test: The thermal response temperature of the polymer was tested using a DSC2000 from Thermomix (TA). 5–10 mg of sample was weighed into an aluminum crucible and heated from 40 °C to 100 °C at a rate of 20 °C / min under a nitrogen atmosphere, holding for 3 min to eliminate thermal history. The sample was then cooled to 0 °C at a rate of 10 °C / min and held for 2 min, followed by a heating rate of 10 °C / min to 100 °C. The data was processed using TA University Analysis software to obtain the melting point of the polymer, i.e., the thermal response temperature.

[0078] (4) Shape Memory Performance Test: The shape memory function of the material was tested using a DMA Q850. The material was fixed on the instrument, heated to 60℃ and held for 5 minutes to ensure sufficient preheating, and the initial strain ε0 was recorded. A constant stress of 0.02–1.5 MPa was applied, and the temperature was lowered to -40℃ at a rate of 10℃ / min, held for 5 minutes, and the maximum strain ε after the applied stress was recorded. max Afterwards, the stress was removed, and the temperature was maintained for 5 minutes. The temporary strain ε after stress removal was recorded. f Then, the temperature was increased to 60℃ at a rate of 10℃ / min and held for 20 minutes until the strain ε remained essentially constant. The strain ε after recovery was then recorded. rThe shape fixation rate R of the sample f (%) and response rate R r (%) is calculated using formula (1) and formula (2) respectively:

[0079]

[0080] The results of the above performance tests are shown in Table 2.

[0081] Table 2 Performance Test Results

[0082]

[0083] (5) Shape memory cycling performance test: The shape memory cycling performance of the material was tested using a DMA Q850. The material was fixed on the instrument, heated to 60℃ and held for 5 minutes to ensure that the material was fully preheated, and ε0 was recorded. A stress was applied to keep the strain constant at 50%, and the temperature was lowered to -40℃ at a rate of 10℃ / min, held for 5 minutes, and ε was recorded. max Afterwards, the stress was removed, the temperature was maintained for 5 minutes, and ε was recorded. f Then, the temperature is increased to 60℃ at a rate of 10℃ / min and held for 15 minutes until ε remains essentially unchanged, and ε is recorded. r The shape fixation rate R of the sample f (%) and response rate R r The percentage (%) is calculated using formulas (1) and (2) respectively. The process is repeated 5 times, and the R value for each cycle is recorded. f and R r The shape memory cycle performance results of the samples in each embodiment are shown in Table 3.

[0084] Table 3. Shape memory cycling performance of materials in each embodiment.

[0085]

[0086]

[0087] Based on the test results, as shown in Table 2, the polycaprolactone shape memory material in the embodiments of the present invention exhibits excellent shape memory performance and mechanical properties, and has an adjustable thermal response temperature. Furthermore, the cured material demonstrates good thermal stability. 5％ The temperatures were all above 342℃. As can be seen from Tables 2 and 3, the polycaprolactone shape memory material in the embodiments of the present invention exhibits excellent shape memory cycling performance, with a shape fixation rate of over 95% and a shape recovery rate of over 86% in 5 cycles.

[0088] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. The above preferred features can be used in any combination without conflict.

Claims

1. A method for preparing a polycaprolactone shape memory material with adjustable response temperature, characterized in that, include: Polycaprolactone-poly(2-vinyl)ethylene glycol copolymer and polythiol compound are cross-linked by UV curing under the action of photoinitiator to obtain polycaprolactone shape memory material with adjustable response temperature. By adjusting the vinyl content, molecular weight, and structure of the polycaprolactone-poly(2-vinyl)ethylene glycol copolymer, the crosslinking density of the crosslinking material can be adjusted, thereby regulating the response temperature of the shape memory material. The polycaprolactone-poly(2-vinyl)ethylene glycol copolymer has the structure shown in the following general formula: R1 is selected from hydrogen, C1-C 20 Alkyl, benzyl, C6-C 14 Aryl, C6-C 14 Oxyheterocycles, C6-C 14 Nitrogen heterocycles, C6-C 14 Sulfur heterocycles, C5-C 20 oxygen heterochain, C5-C 20 Nitrogen heterochains and C5-C 20 Any of the sulfur heterochains; R2, R3, and R4 are selected from C1-C1. 20 Alkyl, benzyl, C6-C 14 Aryl, C6-C 14 Oxyheterocycles, C6-C 14 Nitrogen heterocycles, C6-C 14 Sulfur heterocycles, C5-C 20 oxygen heterochain, C5-C 20 Nitrogen heterochains and C5-C 20 Any of the sulfur heterochains; m, m1, m2, m3, m4, n, n1, n2, n3, and n4 are all positive integers, and m, m1, m2, m3, m4, n, n1, n2, n3, and n4 ≥ 1; The polycaprolactone-poly(2-vinyl)ethylene glycol copolymer has a number average molecular weight of 500 to 100,000 and a vinyl content of 0.10 to 6.40 mmol / g; The polythiol compound is any one of pentaerythritol tetrakis(3-mercaptopropionic acid), trimethylolpropane tris(3-mercaptopropionate), and 1,4-butanediol bis(mercaptoacetate); The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

2. The preparation method according to claim 1, characterized in that, The polycaprolactone-poly(2-vinyl)ethylene glycol copolymer has the structures shown in Formulas 2 and 4, wherein: R2 and R4 are selected from C1-C 20 Alkyl, benzyl, C6-C 14 Aryl, C6-C 14 Oxyheterocycles, C6-C 14 Nitrogen heterocycles, C6-C 14 Sulfur heterocycles, C5-C 20 oxygen heterochain, C5-C 20 Nitrogen heterochains and C5-C 20 Any of the sulfur heterochains; m, m1, m2, m3, m4, n, n1, n2, n3, and n4 are all positive integers, and m, m1, m2, m3, m4, n, n1, n2, n3, and n4 ≥ 1.

3. The preparation method according to claim 2, characterized in that, The polycaprolactone-poly(2-vinyl)ethylene glycol copolymer has the structures shown in Formulas 2 and 4, wherein: R2 is R4 is 4. The preparation method according to claim 1, characterized in that, The amount of each component used in the method is as follows: 80-93 parts of polycaprolactone-poly(2-vinyl)ethylene glycol copolymer, 5-15 parts of polythiol compound, and 2-5 parts of photoinitiator.

5. The preparation method according to claim 1, characterized in that, The process of forming cross-linked materials by UV curing includes reacting under UV irradiation for 1-100 minutes.

6. A polycaprolactone shape memory material with adjustable response temperature, characterized in that, It is prepared using the preparation method described in any one of claims 1-5.

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