Isosorbide-based polyester two-way shape memory material and its preparation method and application

Abstract

This invention discloses an isosorbide-based polyester bidirectional shape memory material, its preparation method, and its applications. The isosorbide-based polyester bidirectional shape memory material includes a shape memory layer and a stress storage layer stacked together. The shape memory layer is composed of semi-crystalline isosorbide-based polyester, and the stress storage layer is composed of elastic isosorbide-based polyester. The isosorbide-based polyester bidirectional shape memory material provided by this invention can reversibly change between different shapes by controlling the temperature, thus expanding the range of materials in the field of biodegradable bidirectional shape memory polymers.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and shape memory polymers, specifically relating to an isosorbide-based polyester bidirectional shape memory material, its preparation method, and its application. Background Technology

[0002] Shape memory is a unique property of smart materials that allows them to recover from a deformed state to its initial state after sensing external stimuli (such as heat, electricity, pH, ionic strength, light, and magnetic fields). Thermotropic shape memory polymers, which are temperature-controlled and simple to design, are a hot research and development area. Polymers exhibit shape memory at specific transition temperatures (such as the glass transition temperature T). g Melting point T m After being shaped, the thermotropic shape memory polymer (TCM) transforms into a temporary shape. When the temperature rises again to the transition temperature, the TCM reverts from the temporary shape to its initial shape. Generally, TCMs contain two relatively independent phases: a stationary phase and a reversible phase. The stationary phase, typically a chemical or physical cross-linking point, maintains the initial shape of the TCM. The reversible phase consists of the mobile molecular chain segments that enable the deformation of the TCM; these segments can undergo glass transition or melt transition with temperature changes. TCMs and their composites have enormous application potential in aerospace, smart electronics, and biomedicine. However, most current reports focus on unidirectional shape memory materials. Unidirectional TCMs can only change shape in a single direction; this process is irreversible and can only be induced to deform once. To induce deformation again with increasing temperature, the TCM needs to be reshaped.

[0003] Therefore, providing a bidirectional shape memory material is an urgent priority. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes an isosorbide-based polyester bidirectional shape memory material, which can be reversibly changed between different shapes by adjusting the temperature. As an aliphatic polyester material, it has certain biodegradable properties, thus expanding the range of materials in the field of biodegradable bidirectional shape memory polymers.

[0005] According to a first aspect of the present invention, an isosorbide-based polyester bidirectional shape memory material is provided, the isosorbide-based polyester bidirectional shape memory material comprising a shape memory layer and a stress storage layer stacked together;

[0006] The shape memory layer comprises a semi-crystalline isosorbide-based polyester;

[0007] The stress storage layer comprises an elastic isosorbide-based polyester.

[0008] According to a second aspect of the present invention, a method for preparing a bidirectional shape memory material of isosorbide-based polyester is provided, comprising the following steps: coating a prepolymer of elastic isosorbide-based polyester onto a prestretched semi-crystalline isosorbide-based polyester and then curing it.

[0009] According to some embodiments of the present invention, the preparation method of the isosorbide-based polyester bidirectional shape memory material includes coating a mixture of an elastic isosorbide-based polyester prepolymer and a photoinitiator onto a pre-stretched semi-crystalline isosorbide-based polyester and then crosslinking and curing it under ultraviolet light to obtain a bilayer structure isosorbide-based polyester bidirectional shape memory material.

[0010] According to some embodiments of the present invention, the irradiance of the ultraviolet light is 1–500 mW / cm². 2 The ultraviolet irradiation time is 10s to 2h.

[0011] According to some embodiments of the present invention, the prepolymer and photoinitiator mixture is obtained by mixing an elastic isosorbide-based polyester with a photoinitiator by solution blending and then removing the solvent.

[0012] According to some embodiments of the present invention, in the pre-stretching step, the elongation of the semi-crystalline isosorbide-based polyester pre-stretched is 5% to 200%.

[0013] The isosorbide-based polyester bidirectional shape memory material of this invention is prepared by pre-stretching a semi-crystalline isosorbide-based polyester at a temperature above its melting point, followed by cooling to fix the deformation. A prepolymer / photoinitiator mixture is obtained by solution blending an elastic isosorbide-based polyester prepolymer with a photoinitiator. A layer of the elastic isosorbide-based polyester prepolymer / photoinitiator mixture is then cast onto the pre-stretched semi-crystalline isosorbide-based polyester and cured by UV crosslinking to obtain a layered composite isosorbide-based polyester bidirectional shape memory material.

[0014] According to some embodiments of the present invention, the raw materials for preparing the semi-crystalline isosorbide-based polyester include a photoinitiator and a prepolymer of the semi-crystalline isosorbide-based polyester.

[0015] According to some embodiments of the present invention, the photoinitiator includes at least one selected from 4-methylbenzophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 2-hydroxy-2-methylphenylacetone.

[0016] According to some embodiments of the present invention, the raw materials for preparing the prepolymer of the semi-crystalline isosorbide-based polyester include: a synthetic monomer of the semi-crystalline isosorbide-based polyester, a catalyst, and a polymerization inhibitor.

[0017] According to some embodiments of the present invention, the polymerization inhibitor includes at least one selected from hydroquinone, 2-tert-butylhydroquinone, p-benzoquinone, and methylhydroquinone.

[0018] According to some embodiments of the present invention, the monomers for synthesizing the semi-crystalline isosorbide-based polyester include unsaturated dicarboxylic acid compounds, saturated dicarboxylic acids, isosorbide, and diols.

[0019] According to some embodiments of the present invention, the unsaturated dicarboxylic acid compounds include unsaturated dicarboxylic acids and unsaturated dicarboxylic acid anhydrides.

[0020] According to some embodiments of the present invention, the unsaturated dicarboxylic acid includes at least one of maleic acid, itaconic acid, and pentenecarboxylic acid.

[0021] According to some embodiments of the present invention, the unsaturated dicarboxylic acid anhydride includes at least one of maleic anhydride and itaconic anhydride.

[0022] According to some embodiments of the present invention, the saturated dicarboxylic acid includes at least one of adipic acid, octanoic acid, sebacic acid, and dodecanoic acid.

[0023] According to some embodiments of the present invention, the diol includes at least one selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol.

[0024] According to some embodiments of the present invention, the catalyst includes at least one selected from stannous chloride, stannous octoate, tetrabutyl titanate, p-toluenesulfonic acid, and concentrated sulfuric acid.

[0025] According to some embodiments of the present invention, the method for preparing the semi-crystalline isosorbide-based polyester includes mixing and dispersing the prepolymer of the semi-crystalline isosorbide-based polyester with a photoinitiator, removing impurities, and performing a crosslinking reaction.

[0026] According to some embodiments of the present invention, the method for preparing the semi-crystalline isosorbide-based polyester includes mixing the prepolymer of the semi-crystalline isosorbide-based polyester with a photoinitiator by solution blending to obtain a mixture, removing the solvent at a temperature of 30-100°C and a vacuum of 1-300 mbar, and then transferring the mixture to ultraviolet light for irradiation crosslinking to obtain a semi-crystalline biodegradable isosorbide-based polyester.

[0027] According to some embodiments of the present invention, the photoinitiator has a mass fraction of 0.01% to 10% in the mixture.

[0028] According to some embodiments of the present invention, the solvent is at least one selected from dichloromethane, trichloromethane, tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, and N,N-dimethylacetamide.

[0029] According to some embodiments of the present invention, the irradiance of the ultraviolet light is 1–500 mW / cm². 2 The ultraviolet irradiation time is 10s to 2h.

[0030] According to some embodiments of the present invention, the method for preparing the prepolymer of the semi-crystalline isosorbide-based polyester includes mixing and reacting the synthetic monomers of the semi-crystalline isosorbide-based polyester, a catalyst and a polymerization inhibitor.

[0031] According to some embodiments of the present invention, in the synthetic monomers of the semi-crystalline isosorbide-based polyester, the molar ratio of the unsaturated diacid compound, the saturated diacid, the isosorbide, and the diol is m:(10-m):n:(10-n). <m≤5,0<n≤5。

[0032] According to some embodiments of the present invention, the method for preparing the prepolymer of the semi-crystalline isosorbide-based polyester includes esterification and polycondensation of a mixture of an unsaturated dicarboxylic acid compound, a saturated dicarboxylic acid, isosorbide, a diol, a catalyst and a polymerization inhibitor.

[0033] According to some embodiments of the present invention, the method for preparing the prepolymer of the semi-crystalline isosorbide-based polyester includes esterification and polycondensation of a mixture of an unsaturated dicarboxylic acid compound, a saturated dicarboxylic acid, isosorbide, a diol, a catalyst of 0.01% to 3% by mass and a polymerization inhibitor of 0.005% to 2% by mass.

[0034] According to some embodiments of the present invention, the esterification reaction is carried out under the following conditions: stirring in a temperature range of 100 to 250°C and a nitrogen atmosphere, with the temperature gradually increased, and the reaction time being 0.1 to 3 hours for every 10°C increase.

[0035] According to some embodiments of the present invention, the conditions for the polycondensation reaction are as follows: after the esterification reaction, the temperature is increased, and under reduced pressure, the mixture is stirred and heated to adjust the reaction temperature to 150-300°C. The reaction is carried out for 0.1-3 hours for every 10°C increase in temperature, thereby synthesizing a semi-crystalline isosorbide-based polyester.

[0036] According to some embodiments of the present invention, the vacuum degree of the decompression condition is <2000 Pa.

[0037] According to some embodiments of the present invention, the raw materials for preparing the elastic isosorbide-based polyester include a photoinitiator and a prepolymer of the elastic isosorbide-based polyester.

[0038] According to some embodiments of the present invention, the photoinitiator includes at least one selected from 4-methylbenzophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 2-hydroxy-2-methylphenylacetone.

[0039] According to some embodiments of the present invention, the raw materials for preparing the prepolymer of the elastic isosorbide-based polyester include: synthetic monomers of elastic isosorbide-based polyester, catalysts and polymerization inhibitors.

[0040] According to some embodiments of the present invention, the polymerization inhibitor includes at least one selected from hydroquinone, 2-tert-butylhydroquinone, p-benzoquinone, and methylhydroquinone.

[0041] According to some embodiments of the present invention, the monomers for synthesizing the elastic isosorbide-based polyester include unsaturated dicarboxylic acid compounds, saturated dicarboxylic acids, isosorbide, and diols.

[0042] According to some embodiments of the present invention, the unsaturated dicarboxylic acid compounds include unsaturated dicarboxylic acids and unsaturated dicarboxylic acid anhydrides.

[0043] According to some embodiments of the present invention, the unsaturated dicarboxylic acid includes at least one of maleic acid, itaconic acid, and pentenecarboxylic acid.

[0044] According to some embodiments of the present invention, the unsaturated dicarboxylic acid anhydride includes at least one of maleic anhydride and itaconic anhydride.

[0045] According to some embodiments of the present invention, the saturated dicarboxylic acid includes at least one of adipic acid, octanoic acid, sebacic acid, and dodecanoic acid.

[0046] According to some embodiments of the present invention, the diol includes at least one selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol.

[0047] According to some embodiments of the present invention, the catalyst includes at least one selected from stannous chloride, stannous octoate, tetrabutyl titanate, p-toluenesulfonic acid, and concentrated sulfuric acid.

[0048] According to some embodiments of the present invention, the method for preparing the prepolymer of the elastic isosorbide-based polyester includes mixing and reacting the prepolymer of the elastic isosorbide-based polyester with synthetic monomers, catalysts and polymerization inhibitors.

[0049] According to some embodiments of the present invention, in the monomers synthesizing the prepolymer of the elastic isosorbide-based polyester, the molar ratio of the unsaturated diacid compound, the saturated diacid, the isosorbide, and the diol is m:(10-m):n:(10-n). <m≤5,2<n≤10。

[0050] This invention utilizes the dehydration esterification and polycondensation reaction of carboxyl and hydroxyl groups between dicarboxylic acids and diols to adjust the proportion of isosorbide components, thereby obtaining two isosorbide-based polyester prepolymers with different properties. Through photocuring and lamination, a biodegradable isosorbide-based polyester is obtained, which has excellent bidirectional shape memory properties.

[0051] According to some embodiments of the present invention, the method for preparing the prepolymer of the elastic isosorbide-based polyester includes esterification and polycondensation of a mixture of an unsaturated dicarboxylic acid compound, a saturated dicarboxylic acid, isosorbide, a diol, a catalyst and a polymerization inhibitor.

[0052] According to some embodiments of the present invention, the preparation method of the prepolymer of the elastic isosorbide-based polyester includes esterification and polycondensation of a mixture of an unsaturated dicarboxylic acid compound, a saturated dicarboxylic acid, isosorbide, a diol, a catalyst with a mass fraction of 0.01% to 3% and a polymerization inhibitor with a mass fraction of 0.005% to 2%.

[0053] According to some embodiments of the present invention, the esterification reaction is carried out under the following conditions: stirring in a temperature range of 100 to 250°C and a nitrogen atmosphere, with the temperature gradually increased, and the reaction time being 0.1 to 3 hours for every 10°C increase.

[0054] According to some embodiments of the present invention, the conditions for the polycondensation reaction are as follows: after the esterification reaction, the temperature is increased, and under reduced pressure, the mixture is stirred and heated to adjust the reaction temperature to 150-300°C, and the reaction is carried out for 0.1-3 hours for every 10°C increase, thereby synthesizing a prepolymer of elastic isosorbide-based polyester.

[0055] The method for preparing the isosorbide-based polyester bidirectional shape memory material of the present invention involves first synthesizing a prepolymer of semi-crystalline isosorbide-based polyester and a prepolymer of elastic isosorbide-based polyester, respectively; then blending the two unsaturated prepolymers with a photoinitiator; placing the prepolymer of semi-crystalline isosorbide-based polyester mixed with the photoinitiator under ultraviolet light for crosslinking and curing to obtain semi-crystalline isosorbide-based polyester; pre-stretching the semi-crystalline isosorbide-based polyester at a temperature above its melting point and cooling to fix its shape; then casting a layer of unsaturated prepolymer of elastic isosorbide-based polyester mixed with the photoinitiator on it; and then transferring it under ultraviolet light for crosslinking and curing to obtain an isosorbide-based polyester with a bilayer structure, and the polyester has bidirectional shape memory function.

[0056] According to a third aspect of the present invention, an application of the isosorbide-based polyester bidirectional shape memory material prepared by the above preparation method in the field of smart materials is proposed.

[0057] According to some embodiments of the present invention, the field of smart materials includes aerospace, smart electronics, and biomedicine. Detailed Implementation

[0058] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0059] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0060] Example 1

[0061] This embodiment provides a biodegradable isosorbide-based polyester bidirectional shape memory material and its preparation method, specifically the following steps:

[0062] S1. Itaconic acid, sebacic acid, isosorbide, 1,4-butanediol, and 1,6-hexanediol were added to the reaction apparatus according to the proportions in Table 1. Then, 0.2% (w / w) of stannous chloride catalyst and 0.05% (w / w) of hydroquinone polymerization inhibitor were added to the reaction apparatus. The mixture was stirred continuously under a nitrogen atmosphere at a temperature range of 160–200°C, and the temperature was gradually increased to carry out the esterification reaction, reacting for 1 hour for every 10°C increase. The temperature was further increased, and under reduced pressure (200 Pa), the mixture was stirred and heated to carry out the polycondensation reaction, adjusting the reaction temperature to 210–260°C, reacting for 1 hour for every 10°C increase, to synthesize a semi-crystalline, biodegradable isosorbide-based polyester prepolymer.

[0063] Table 1. Partial composition of the prepolymer of semi-crystalline isosorbide-based polyester-1

[0064] Component Name molar ratio Component Name molar ratio Itaconic acid 2 Isosorbide 1 sebacic acid 8 1,4-Butanediol 4.5 1,6-Hexanediol 4.5

[0065] S2. Itaconic acid, sebacic acid, isosorbide, 1,4-butanediol, and 1,6-hexanediol were added to the reaction apparatus according to the proportions in Table 2. Then, 0.2% (w / w) of stannous chloride catalyst and 0.05% (w / w) of hydroquinone inhibitor were added to the reaction apparatus. The mixture was stirred continuously under a nitrogen atmosphere at a temperature range of 160–200°C, and the temperature was gradually increased to carry out the esterification reaction, reacting for 1 hour for every 10°C increase. The temperature was further increased, and under reduced pressure (200 Pa), the mixture was stirred and heated to carry out the polycondensation reaction, adjusting the reaction temperature to 210–260°C, reacting for 1 hour for every 10°C increase, to synthesize a prepolymer of elastic biodegradable isosorbide-based polyester.

[0066] Table 2. Prepolymer Components of Elastic Isosorbide Polyester-1

[0067] Component Name molar ratio Component Name molar ratio Itaconic acid 2 Isosorbide 4 sebacic acid 8 1,4-Butanediol 3 1,6-Hexanediol 3

[0068] S3. The semi-crystalline biodegradable isosorbide-based polyester unsaturated prepolymer synthesized in step S1 is mixed uniformly with the photoinitiator 4-methylbenzophenone by solution blending. The mass fraction of the photoinitiator in the mixture is 0.5%, and the solvent used in the mixing is dichloromethane. The solvent is then removed using a rotary evaporator at 70°C and a reduced pressure of 80 mbar. The resulting mixture is poured into a mold of a certain shape and transferred to an irradiation site with an intensity of 200 mW / cm². 2 Irradiation under ultraviolet light for 5 min crosslinking yields a semi-crystalline, biodegradable isosorbide-based polyester.

[0069] S4. The semi-crystalline biodegradable isosorbide-based polyester prepared in step S3 is pre-stretched at 60°C to a deformation of 100%, and then cooled to 25°C to fix the deformation. The unsaturated prepolymer of the elastic biodegradable isosorbide-based polyester synthesized in S2 is mixed uniformly with the photoinitiator 4-methylbenzophenone by solution blending. After removing the solvent dichloromethane in the same manner as above, the prepolymer / photoinitiator mixture is obtained. A layer of the elastic isosorbide-based polyester prepolymer / photoinitiator mixture is cast onto the pre-stretched semi-crystalline isosorbide-based polyester and irradiated at an intensity of 200 mW / cm². 2 Irradiation under ultraviolet light for 5 min crosslinking yields a layered composite structure of isosorbide-based polyester bidirectional shape memory material;

[0070] Steps S1 and S2 are not in any particular order.

[0071] The biodegradable isosorbide-based polyester prepared in this embodiment can be bent at temperatures above the melting point of semi-crystalline polyester-1 (>60°C), and partially recover when cooled to below the crystallization temperature (<30°C). The different states can be switched by temperature control. Performance test results are shown in Tables 3 and 4.

[0072] Table 3 Thermal properties of isosorbide-based polyester-1

[0073]

[0074] Table 4 Mechanical properties of isosorbide-based polyester-1

[0075]

[0076] Table 5. Degradation rate of isosorbide-based polyester-1 in a one-month composting disintegration experiment.

[0077]

[0078] Example 2

[0079] This embodiment provides a biodegradable isosorbide-based polyester bidirectional shape memory material and its preparation method. The steps not specifically described are the same as those in Example 1. The difference is that the ratio of the monomer components in the prepolymer of the semi-crystalline biodegradable isosorbide-based polyester and the elastic biodegradable isosorbide-based polyester is as shown in Tables 6 and 7 below. The resulting material is named isosorbide-based polyester-2.

[0080] Table 6. Prepolymer Components of Semi-crystalline Isosorbide-based Polyester-2

[0081] Component Name molar ratio Component Name molar ratio Itaconic acid 2 Isosorbide 2 sebacic acid 8 1,4-Butanediol 4 1,6-Hexanediol 4

[0082] Table 7. Prepolymer Components of Elastic Isosorbide Polyester-2

[0083] Component Name molar ratio Component Name molar ratio Itaconic acid 2 Isosorbide 6 sebacic acid 8 1,4-Butanediol 2 1,6-Hexanediol 2

[0084] The biodegradable isosorbide-based polyester prepared in this embodiment exhibits excellent bidirectional shape memory properties, allowing it to switch between bent and semi-bent states via temperature control. The shape memory switching temperatures are: bending at temperatures above the melting point of the semi-crystalline polyester-2 (>40℃) and bending at temperatures below the crystallization point (<10℃). Performance test results are shown in Tables 8 and 9.

[0085] Table 8 Thermal properties of isosorbide-based polyester-2

[0086]

[0087] Table 9 Mechanical properties of isosorbide-based polyester-2

[0088]

[0089]

[0090] Table 10. Degradation rate of isosorbide-based polyester-2 in a one-month composting disintegration experiment.

[0091]

[0092] Example 3

[0093] This embodiment provides a biodegradable isosorbide-based polyester bidirectional shape memory material and its preparation method. The difference from Example 1 is that the unsaturated dicarboxylic acid itaconic acid in the synthetic monomer is replaced with the unsaturated dicarboxylic acid anhydride maleic anhydride. The resulting material is named isosorbide-based polyester-3. The specific steps are as follows:

[0094] S1. Maleic anhydride, sebacic acid, isosorbide, 1,4-butanediol, and 1,6-hexanediol were added to the reaction apparatus according to the proportions in Table 11. Then, stannous chloride (0.1 wt%), p-toluenesulfonic acid (0.1 wt%), hydroquinone (0.03 wt%), and methylhydroquinone (0.03 wt%) were added to the reaction apparatus as catalysts. The mixture was stirred continuously at a temperature range of 140–180 °C under a nitrogen atmosphere to carry out the esterification reaction, with each 10 °C increase lasting 1 hour. The temperature was then further increased, and under reduced pressure (200 Pa), the mixture was stirred and heated to carry out the polycondensation reaction, adjusting the reaction temperature to 200–250 °C, with each 10 °C increase lasting 1 hour, to synthesize a semi-crystalline, biodegradable isosorbide-based polyester prepolymer.

[0095] Table 11. Partial composition of the prepolymer of semi-crystalline biodegradable isosorbide-based polyester-3

[0096] Component Name molar ratio Component Name molar ratio Maleic anhydride 2 Isosorbide 1 sebacic acid 8 1,4-Butanediol 4.5 1,6-Hexanediol 4.5

[0097] S2. Maleic anhydride, sebacic acid, isosorbide, 1,4-butanediol, and 1,6-hexanediol were added to the reaction apparatus according to the proportions in Table 12. Then, stannous chloride (0.1 wt%), p-toluenesulfonic acid (0.1 wt%), hydroquinone (0.03 wt%), and methylhydroquinone (0.03 wt%) were added to the reaction apparatus as catalysts. The mixture was stirred continuously at a temperature range of 140–180 °C under a nitrogen atmosphere to carry out the esterification reaction, with each 10 °C increase lasting 1 hour. The temperature was then further increased, and under reduced pressure (200 Pa), the mixture was stirred and heated to carry out the polycondensation reaction, adjusting the reaction temperature to 200–250 °C, with each 10 °C increase lasting 1 hour, to synthesize a prepolymer of elastic, biodegradable isosorbide-based polyester.

[0098] Table 12. Prepolymer Components of Elastic Biodegradable Isosorbide-Based Polyester-3

[0099] Component Name molar ratio Component Name molar ratio Maleic anhydride 2 Isosorbide 4 sebacic acid 8 1,4-Butanediol 3 1,6-Hexanediol 3

[0100] S3. The semi-crystalline biodegradable isosorbide-based polyester unsaturated prepolymer synthesized in step S1 is mixed uniformly with the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone by solution blending. The mass fraction of the photoinitiator in the mixture is 1%, and the solvent used in the mixing is dichloromethane. The solvent is then removed using a rotary evaporator at 70°C and a reduced pressure of 80 mbar. The resulting mixture is poured into a mold of a certain shape and transferred to an irradiation site with an intensity of 100 mW / cm². 2 Irradiation under ultraviolet light for 8 min crosslinking yielded a semi-crystalline, biodegradable isosorbide-based polyester.

[0101] S4. The semi-crystalline biodegradable isosorbide-based polyester prepared in step S3 is pre-stretched at 60°C to a deformation of 100%, and then cooled to 25°C to fix the deformation. The unsaturated prepolymer of the elastic biodegradable isosorbide-based polyester synthesized in step 2 is mixed uniformly with the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone by solution blending. After removing the solvent dichloromethane in the same manner as above, the prepolymer / photoinitiator mixture is obtained. A layer of the elastic isosorbide-based polyester prepolymer / photoinitiator mixture is cast onto the pre-stretched semi-crystalline isosorbide-based polyester and irradiated at an intensity of 100 mW / cm². 2 Irradiation under ultraviolet light for 8 min crosslinking yields a layered composite structure of isosorbide-based polyester bidirectional shape memory material;

[0102] Steps S1 and S2 are not in any particular order.

[0103] The biodegradable isosorbide-based polyester prepared in this embodiment exhibits excellent bidirectional shape memory properties, allowing it to switch between bent and semi-bent states via temperature control. The shape memory switching temperatures are: bending at temperatures above the melting point of the semi-crystalline polyester-3 (>55℃) and bending at temperatures below the crystallization point (<25℃). The test results are shown in Tables 13 and 14.

[0104] Table 13 Thermal properties of isosorbide-based polyester-3

[0105]

[0106] Table 14 Mechanical properties of isosorbide-based polyester-3

[0107]

[0108] Table 15 Degradation rate of isosorbide-based polyester-3 in a one-month composting disintegration experiment.

[0109]

[0110] Example 4

[0111] This embodiment provides a biodegradable isosorbide-based polyester bidirectional shape memory material and its preparation method. The difference from the above embodiments lies in that the synthetic monomer components of the semi-crystalline biodegradable isosorbide-based polyester and the elastic biodegradable isosorbide-based polyester prepolymer are not entirely the same. The specific steps are as follows:

[0112] S1. Itaconic acid, sebacic acid, isosorbide, and 1,6-hexanediol were added to the reaction apparatus according to the proportions in Table 16. Tetrabutyl titanate (0.2 wt%) and methylhydroquinone (0.05 wt%) were then added to the apparatus. The mixture was stirred continuously under a nitrogen atmosphere within a temperature range of 160–200 °C to carry out the esterification reaction, with each 10 °C increase lasting 1 hour. The temperature was then further increased under reduced pressure (200 Pa) with stirring to carry out the polycondensation reaction, adjusting the reaction temperature to 210–260 °C, with each 10 °C increase lasting 1 hour. This synthesized a semi-crystalline, biodegradable isosorbide-based polyester prepolymer. The test results are shown in Tables 16 and 17.

[0113] Table 16. Partial Components of Semi-Crystalline Biodegradable Isosorbide-Based Polyester-4 Prepolymer

[0114] Component Name molar ratio Component Name molar ratio Itaconic acid 1 Isosorbide 4 sebacic acid 9 1,6-Hexanediol 6

[0115] S2. Itaconic acid, sebacic acid, isosorbide, ethylene glycol, 1,4-butanediol, and 1,6-hexanediol were added to the reaction apparatus according to the proportions in Table 17. Then, stannous chloride (0.1 wt%), p-toluenesulfonic acid (0.1 wt%), hydroquinone (0.05 wt%), and methylhydroquinone (0.05 wt%) were added to the reaction apparatus as catalysts. The mixture was stirred continuously at a temperature range of 160–200 °C under a nitrogen atmosphere to carry out the esterification reaction, with each 10 °C increase lasting 1 hour. The temperature was then further increased, and under reduced pressure (200 Pa), the mixture was stirred and heated to carry out the polycondensation reaction, adjusting the reaction temperature to 210–260 °C, with each 10 °C increase lasting 1 hour, to synthesize a prepolymer of elastic biodegradable isosorbide-based polyester.

[0116] Table 17. Partial Components of the Prepolymer of Elasto-Biodegradable Isosorbide-Based Polyester-4

[0117] Component Name molar ratio Component Name molar ratio Itaconic acid 1 Isosorbide 4 sebacic acid 9 Ethylene glycol 2 1,4-Butanediol 2 1,6-Hexanediol 2

[0118] S3. The semi-crystalline biodegradable isosorbide-based polyester unsaturated prepolymer synthesized in step S1 is mixed uniformly with the photoinitiator 2-hydroxy-2-methylphenylacetone by solution blending. The mass fraction of the photoinitiator in the mixture is 0.5%, and the solvent used in the mixing is dichloromethane. The solvent is then removed using a rotary evaporator at 80°C and a reduced pressure of 80 mbar. The resulting mixture is poured into a mold of a certain shape and transferred to an irradiation site with an intensity of 500 mW / cm². 2 Irradiation under ultraviolet light for 3 min crosslinking yields a semi-crystalline, biodegradable isosorbide-based polyester.

[0119] S4. The semi-crystalline biodegradable isosorbide-based polyester prepared in step S3 is pre-stretched at 80°C above its melting point until the deformation reaches 100%, and then cooled to 20°C to fix the deformation. The unsaturated prepolymer of the elastic biodegradable isosorbide-based polyester synthesized in step 2 is mixed uniformly with the photoinitiator 2-hydroxy-2-methylphenylacetone by solution blending. After removing the solvent dichloromethane in the same manner as above, the prepolymer / photoinitiator mixture is obtained. A layer of the elastic isosorbide-based polyester prepolymer / photoinitiator mixture is cast onto the pre-stretched semi-crystalline isosorbide-based polyester and irradiated at an intensity of 500 mW / cm². 2 Irradiation under ultraviolet light for 3 min crosslinking yields a layered composite structure of isosorbide-based polyester bidirectional shape memory material;

[0120] Steps S1 and S2 are not in any particular order.

[0121] The biodegradable isosorbide-based polyester prepared in this embodiment consists of a semi-crystalline biodegradable isosorbide-based copolyester with unidirectional shape memory function as the upper layer and a biodegradable isosorbide-based copolyester with excellent elastic properties as the lower layer. The bilayer isosorbide-based polyester material obtained through lamination not only has biodegradability but also exhibits excellent bidirectional shape memory function. The shape memory switching temperatures are the temperatures above the melting point of the semi-crystalline polyester (>70℃) and the temperatures below the crystallization point (<40℃), and the test results are shown in Tables 18 and 19.

[0122] Table 18 Thermal properties of isosorbide-based polyester-4

[0123]

[0124] Table 19 Mechanical Properties of Isosorbide-based Polyester-4

[0125]

[0126] Table 20 Degradation rate of isosorbide-based polyester-4 in a one-month composting disintegration experiment.

[0127]

[0128] Comparative Example 1

[0129] This comparative example provides a biodegradable isosorbide-based polyester bidirectional shape memory material and its preparation method. The steps not specifically described are the same as in Example 1, except that the itaconic acid of the prepolymer of the semi-crystalline biodegradable isosorbide-based polyester and the elastic biodegradable isosorbide-based polyester is replaced with acrylic acid, and the other conditions are the same.

[0130] The biodegradable isosorbide-based polyester prepared in this comparative example has a semi-crystalline biodegradable isosorbide-based copolyester with unidirectional shape memory function on the upper layer and a biodegradable isosorbide-based copolyester with elastic properties on the lower layer. Performance tests show that the tensile strength, elongation at break and Young's modulus of the semi-crystalline polyester decreased by 5-7%.

[0131] The introduction of acrylonitrile alters the arrangement of polymer chains, leading to decreased crystallinity and stronger interactions between the chains, thus increasing the energy required for elongation at break. Consequently, this results in a decrease in the material's tensile strength, elongation at break, and Young's modulus.

[0132] Comparative Example 2

[0133] This comparative example provides a biodegradable isosorbide-based polyester bidirectional shape memory material and its preparation method. The steps not specifically described are the same as in Example 1, except that the sebacic acid of the prepolymer of the semi-crystalline biodegradable isosorbide-based polyester and the elastic biodegradable isosorbide-based polyester is replaced with succinic acid, and the other conditions are the same.

[0134] The biodegradable isosorbide-based polyester prepared in this comparative example has a semi-crystalline biodegradable isosorbide-based copolyester with unidirectional shape memory function on the upper layer and a biodegradable isosorbide-based copolyester with elastic properties on the lower layer. Performance tests show that the Young's modulus of the semi-crystalline polyester decreased by about 8%.

[0135] The introduction of succinic acid increases the flexibility of the polymer chain, making the material more prone to deformation and fracture under stress, thereby reducing the elongation at break and Young's modulus.

[0136] As can be seen from the above examples, adjusting the composition and composition ratio of the synthetic monomers can effectively control the thermal and mechanical properties of polyesters, and can be used to design and prepare bidirectional shape memory materials with different switching temperatures to adapt to different application fields.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An isosorbide-based polyester bidirectional shape memory material, characterized in that, The isosorbide-based polyester bidirectional shape memory material includes a shape memory layer and a stress storage layer stacked together. The shape memory layer comprises a semi-crystalline isosorbide-based polyester; The stress storage layer comprises an elastic isosorbide-based polyester; The raw materials for preparing the semi-crystalline isosorbide-based polyester include a photoinitiator and a prepolymer of the semi-crystalline isosorbide-based polyester. The photoinitiator includes at least one of 4-methylbenzophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone and 2-hydroxy-2-methylphenylpropanone; The raw materials for preparing the prepolymer of the semi-crystalline isosorbide-based polyester include: the synthetic monomer of the semi-crystalline isosorbide-based polyester, a catalyst, and a polymerization inhibitor; The monomers for synthesizing the semi-crystalline isosorbide-based polyester include unsaturated dicarboxylic acid compounds, saturated dicarboxylic acids, isosorbide, and diols. The catalyst includes at least one of stannous chloride, stannous octanoate, tetrabutyl titanate, p-toluenesulfonic acid, and concentrated sulfuric acid; The polymerization inhibitor includes at least one of hydroquinone, 2-tert-butylhydroquinone, p-benzoquinone, and methylhydroquinone; The method for preparing the semi-crystalline isosorbide-based polyester includes mixing and dispersing the prepolymer of the semi-crystalline isosorbide-based polyester with a photoinitiator, removing impurities, and performing a crosslinking reaction. The method for preparing the prepolymer of the semi-crystalline isosorbide-based polyester includes mixing and reacting the synthetic monomers, catalyst and polymerization inhibitor of the semi-crystalline isosorbide-based polyester. In the monomers for synthesizing the semi-crystalline isosorbide-based polyester, the molar ratio of the unsaturated dicarboxylic acid compound, the saturated dicarboxylic acid, the isosorbide, and the diol is m:(10-m):n:(10-n). <m≤5,0<n≤5; The raw materials for preparing the elastic isosorbide-based polyester include a photoinitiator and a prepolymer of the elastic isosorbide-based polyester. The photoinitiator includes at least one of 4-methylbenzophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone and 2-hydroxy-2-methylphenylpropanone; The raw materials for preparing the prepolymer of the elastic isosorbide-based polyester include: synthetic monomers of elastic isosorbide-based polyester, catalysts and polymerization inhibitors; The polyester monomers of the elastic isosorbide-based polyester include unsaturated dicarboxylic acid compounds, saturated dicarboxylic acids, isosorbide, and diols. The catalyst includes at least one of stannous chloride, stannous octanoate, tetrabutyl titanate, p-toluenesulfonic acid, and concentrated sulfuric acid; The polymerization inhibitor includes at least one of hydroquinone, 2-tert-butylhydroquinone, p-benzoquinone, and methylhydroquinone; The method for preparing the prepolymer of the elastic isosorbide-based polyester includes mixing and reacting the prepolymer of the elastic isosorbide-based polyester with synthetic monomers, catalysts and polymerization inhibitors; In the polyester monomers of the prepolymer of the elastic isosorbide-based polyester, the molar ratio of the unsaturated diacid compound, the saturated diacid, the isosorbide, and the diol is m:(10-m):n:(10-n), 0 <m≤5,2<n≤10。 2. A method for preparing the isosorbide-based polyester bidirectional shape memory material as described in claim 1, characterized in that, The process involves coating a prepolymer of elastic isosorbide-based polyester and a photoinitiator onto a pre-stretched, semi-crystalline isosorbide-based polyester and then crosslinking and curing it under ultraviolet light.

3. The preparation method according to claim 2, characterized in that, In the pre-stretching step, the elongation of the semi-crystalline isosorbide-based polyester pre-stretched is 5% to 200%.

4. The application of the isosorbide-based polyester bidirectional shape memory material as described in claim 1 in the field of smart material preparation.

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