Preparation and Temporary Shape Control Method of a Degradable Shape Memory Polyester Copolymer

Abstract

The present invention discloses a preparation method of a degradable shape memory polyester copolymer and a method for controlling its temporary shape. The preparation method of the polyester copolymer comprises the following steps: using one of lactide, lactic acid, glycolide, methyl glycolate, and glycolic acid as a monomer to carry out an esterification reaction to prepare a hard segment prepolymer; using adipic acid or succinic acid and butanediol to carry out an esterification reaction to prepare a soft segment prepolymer; or using caprolactone as a polymerization monomer to prepare a soft segment prepolymer; and carrying out a melt polymerization reaction on the hard segment prepolymer and the soft segment prepolymer to obtain a degradable shape memory polyester copolymer. The degradable shape memory polyester copolymer prepared by the present invention has the advantages of good mechanical properties, adjustable deformation temperature range, and degradability, and can be used as a raw material for products such as food and tableware packaging, fracture fixation materials, and smart fabrics.

Description

Technical Field

[0001] The present invention relates to the preparation and application of a degradable shape memory polymer, and particularly to the preparation of a degradable shape memory polyester copolymer and a method for controlling a temporary shape. Background Art

[0002] Shape memory polymers can be deformed under external stimuli (such as temperature, force, light, humidity, etc.) and fix the temporary shape after deformation under specific conditions, and can return to the original shape when stimulated again. Due to many advantages such as light weight, low cost, easy molding, large deformability, adjustable memory temperature, etc., shape memory polymers are widely used as heat shrinkable films, heat shrinkable tubes, smart fabrics, medical materials, etc.

[0003] Degradable polymers are environmentally friendly materials because they can be quickly degraded into small molecule substances such as water and carbon dioxide under natural conditions, and have been applied in fields such as agricultural mulch films, packaging bags, and medical materials. Using degradable polymers instead of traditional polymer products such as plastics is an effective way to reduce the environmental impact of plastics.

[0004] Most shape memory polymers are new polymers with special structures formed by in-situ polymerization. These polymer materials are designed for specific requirements in special situations, and their application fields are relatively narrow, generally not considering degradability; while heat shrinkable films, tubes, etc. used in daily life are mostly made of modified general resins as raw materials, and these shape memory polymers do not have degradability.

[0005] Preparing shape memory materials using degradable polymers has less impact on the ecological environment while maintaining the shape memory performance of the materials, greatly expanding the application fields of degradable polymer materials. However, shape memory polymer materials usually contain two structures: a "fixed phase" and a "reversible phase". To make the material have a strong shape recovery force, usually two methods are adopted: one is to increase the crosslinking density of the "fixed phase", so as to store more entropy energy of molecular chains during the stretching process. As the temperature rises, the stored entropy energy is released, driving the material to return to the original shape. However, crosslinking of degradable polymers will inevitably weaken or even completely destroy their degradability. The other is to introduce rigid chain segments to increase the entropy energy of molecular chains during stretching, so as to provide a large recovery force for shape recovery. But like increasing the crosslinking density, this method is also not conducive to polymer degradation, and introducing rigid chain segments may reduce the safety of the material and is no longer suitable for fields such as food packaging and medical and health. Summary of the Invention

[0006] Objective of the Invention: The objective of the present invention is to provide a preparation method of a degradable shape memory polyester copolymer, and solve the problem of how to prepare a degradable shape memory polyester copolymer. Another objective of the present invention is to propose a temporary shape control method for the degradable shape memory polyester copolymer, and solve the problem of how to recover and fix the shape of the polyester copolymer.

[0007] Technical Solution: The preparation method of a degradable shape memory polyester copolymer according to the present invention includes the following steps:

[0008] (1) Using one of lactide, lactic acid, glycolide, methyl glycolate, and glycolic acid as a monomer, and carrying out an esterification reaction to prepare a hard segment prepolymer;

[0009] (2) Using adipic acid or succinic acid and butanediol to carry out an esterification reaction to prepare a soft segment prepolymer; or using caprolactone as a polymerization monomer to prepare a soft segment prepolymer;

[0010] (3) Carrying out a melt polymerization reaction on the hard segment prepolymer and the soft segment prepolymer to obtain a degradable shape memory polyester copolymer.

[0011] The present invention uses a degradable polyester monomer as the main raw material, obtains hard and soft segment prepolymers through an esterification reaction, and adjusts the ratio of the hard and soft segments during the polymerization stage to polymerize and obtain a degradable shape memory polyester copolymer with different shape fixing temperatures and recovery temperatures, as well as different shape fixing rates and recovery rates.

[0012] Preferably, in step (1), the method of the esterification reaction is: mixing the monomer and 0.1-0.25% of the total weight of the monomer of the first catalyst, and heating to 140-180°C in an inert atmosphere to carry out the esterification reaction. After reacting for 3-7h, a hard segment prepolymer is obtained.

[0013] Preferably, the first catalyst is one or more of tin octoate, stannous octoate, stannous oxide, stannous chloride, stannous oxalate, tin tetrachloride, titanium butoxide, p-toluenesulfonic acid monohydrate, anhydrous zinc acetate, triethoxy tetrafluoroborate, boron trifluoride, trifluoroacetic acid, and antimony trioxide.

[0014] Preferably, in step (2), the method of the esterification reaction is: adding a second catalyst to a mixture of adipic acid and butanediol or a mixture of succinic acid and butanediol, and heating to 160-200°C in an inert atmosphere to carry out the esterification reaction. After reacting for 4-8h, a soft segment prepolymer is obtained;

[0015] The method of using caprolactone as a polymerization monomer to prepare a soft segment prepolymer is: adding a second catalyst to caprolactone, and carrying out an esterification reaction under vacuum and heating conditions to obtain a soft segment prepolymer.

[0016] Preferably, the molar ratio of adipic acid to butanediol is 1 - 1.2:1 - 1.2, the molar ratio of succinic acid to butanediol is 1 - 1.2:1 - 1.2, the second catalyst includes one or more of tetrabutyl titanate, tetraphenyltin, stannous octoate, and the addition amount of the second catalyst is 0.1 - 0.25 wt% of the mixture of adipic acid and butanediol or the mixture of succinic acid and butanediol or caprolactone.

[0017] Preferably, in step (3), the molar ratio of the hard segment prepolymer to the soft segment prepolymer is 1 - 9:1 - 9.

[0018] Preferably, in step (3), the method of melt polymerization is as follows: under an inert atmosphere, the hard segment prepolymer and the soft segment prepolymer are mixed and melted, and then a third catalyst, triphenyl phosphate, and an antioxidant are added. Esterification reaction is carried out for 3 - 7 h under vacuum conditions at 180 - 220 °C to obtain a degradable shape - memory polyester copolymer; the weight ratio of the total weight of the hard segment prepolymer and the soft segment prepolymer: the third catalyst: triphenyl phosphate: antioxidant is 100:0.1 - 0.25:0.1 - 0.3:0.1 - 0.3.

[0019] Preferably, the third catalyst includes one or more of antimony trioxide, tetrabutyl titanate, tin isooctoate, stannous octoate, and the method of mixing and melting the hard segment prepolymer and the soft segment prepolymer is as follows: first, the soft segment prepolymer is heated to 175 - 195 °C under stirring conditions and kept warm for 0.5 - 1.5 h, then cooled to 130 - 150 °C and the hard segment prepolymer is added, and kept warm until the soft segment prepolymer and the hard segment prepolymer are completely melted.

[0020] On the other hand, the present invention discloses a method for controlling the temporary shape of the degradable shape - memory polyester copolymer prepared by the above - mentioned preparation method, including the following steps:

[0021] The polyester copolymer is stretched when the temperature is higher than the crystallization temperature of its soft segment and lower than the crystallization temperature of its hard segment, and then cooled to a temperature lower than the crystallization temperature of its soft segment to fix the stretched shape.

[0022] Preferably, the crystallization temperature of the soft segment is 30 - 45 °C, and the crystallization temperature of the hard segment is 65 - 160 °C.

[0023] In the degradable shape memory polyester copolymer of the present invention, there are two types of hard and soft segments. Among them, the hard segment serves as the "fixed phase". Above the transition temperature (between the "reversible phase" crystallization temperature and the "fixed phase" crystallization temperature), under the action of tensile force, this phase is cold-drawn into a highly oriented structure, and the molecular chains are arranged along the direction of the applied force. The conformational entropy of the molecular chains decreases, and the entropy energy increases. As the temperature drops below the transition temperature, the molecular chains are frozen and their movement is hindered. After removing the external force, the conformation of the molecular chains remains unchanged, and the entropy energy is stored. When the temperature rises above the transition temperature again, the movement ability of the molecular chains is activated, the entropy energy is released, driving the molecular chains back to the state with the maximum conformational entropy, and the material returns to its original shape. The soft segment serves as the "reversible phase". When stretched above the transition temperature, since the molecular chains of this phase have strong movement ability at this temperature, the stretched molecular chains quickly rearrange. As the temperature drops below the transition temperature, all the molecular chains of the two phases are frozen, and the temporary shape is fixed after removing the external force. When the temperature rises above the transition temperature again, on the one hand, the molecular chains of the "fixed phase" are activated and the entropy energy is released. On the other hand, the freezing of the molecular chains of the "reversible phase" is released, and the hindering effect on the molecular chains of the "fixed phase" is weakened. The material returns to its original shape under the drive of the entropy energy.

[0024] In the present invention, polylactic acid or polyglycolic acid is used as the hard segment, serving as the "fixed phase" in the shape memory polyester copolymer, which is used to provide the driving force for shape recovery and fix the original shape of the polyester. Polybutylene adipate, polybutylene succinate or polycaprolactone is used as the soft segment, serving as the "reversible phase" in the shape memory polyester copolymer, which is used to control the fixation and recovery of the temporary shape of the polyester.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: The degradable shape memory polyester copolymer prepared by the present invention has the advantages of good mechanical properties, adjustable deformation temperature range, and degradability, and can be used as raw materials for products such as food and tableware packaging, fracture fixation materials, and smart fabrics. Description of the Drawings

[0026] Figure 1 It is the shape memory performance test curve of the lactic acid-butylene adipate copolymer;

[0027] Figure 2 It is the stress-strain curve of the lactic acid-butylene adipate copolymer;

[0028] Figure 3 It is the weight loss curve of the lactic acid-butylene adipate copolymer in water, soil burial, and CALB enzyme environments respectively. Detailed Embodiments

[0029] The technical solutions of the present invention will be further described below with reference to the accompanying drawings.

[0030] Example 1: The preparation method of a degradable shape memory polyester copolymer is as follows:

[0031] (1) Preparation of lactic acid prepolymer:

[0032] Weigh a certain mass of lactic acid into a reaction kettle, add 0.2% of anhydrous zinc acetate as a catalyst based on the weight of lactic acid, protect with nitrogen, heat up to 160 °C, start stirring, after reacting for 5 hours, turn off the nitrogen, evacuate for 10 minutes, and finally obtain the lactic acid prepolymer.

[0033] (2) Preparation of adipic acid butanediol prepolymer:

[0034] Add adipic acid and 1,4-butanediol with a molar ratio of 1:1 into a reaction kettle, add 0.2% of tetrabutyl titanate as a catalyst based on the total weight of adipic acid and butanediol, evacuate and then displace the residual air with nitrogen and continuously protect with nitrogen, heat up to 180 °C, start stirring, after reacting for 6 hours, turn off the nitrogen, and obtain an adipic acid butanediol prepolymer with a number average molecular weight of 8917.

[0035] (3) Melt polymerization of lactic acid prepolymer and adipic acid butanediol prepolymer:

[0036] Add the adipic acid butanediol prepolymer into a reaction kettle, displace the air with nitrogen, set the temperature at 50 °C, start stirring, gradually heat up to 185 °C and keep it warm for 1 hour, then cool down to 140 °C and add the same molar amount of lactic acid prepolymer as the adipic acid butanediol prepolymer, and then add 0.2% of antimony trioxide as a catalyst, 0.2% of triphenyl phosphate as a stabilizer, and 0.2% of antioxidant 1010 based on the total weight of the adipic acid butanediol prepolymer and the lactic acid prepolymer. Evacuate, gradually heat up to 200 °C, and keep it warm for 5 hours to obtain a lactic acid adipic acid butanediol ester copolymer, which is the degradable shape memory polyester copolymer.

[0037] Example 2: The preparation method of a degradable shape memory polyester copolymer is as follows:

[0038] (1) Preparation of lactic acid prepolymer:

[0039] Weigh a certain mass of lactic acid into a reaction kettle, add 0.25% of anhydrous zinc acetate based on the weight of lactic acid, protect with nitrogen, heat up to 140 °C, start stirring, after reacting for 7 hours, turn off the nitrogen, evacuate for 10 minutes, and finally obtain the lactic acid prepolymer.

[0040] (2) Preparation of succinic acid butanediol prepolymer:

[0041] Add succinic acid and 1,4-butanediol with a molar ratio of 1.2:1 into a reaction kettle, add tetrabutyl titanate as a catalyst accounting for 0.25% of the total weight of succinic acid and butanediol, evacuate the air, displace the residual air with nitrogen and continuously introduce nitrogen for protection, heat up to 160 °C, start stirring, and after reacting for 8 hours, close the nitrogen to obtain a succinic acid-butanediol prepolymer with a number-average molecular weight of 7825.

[0042] (3) Melt polymerization of lactic acid prepolymer and succinic acid-butanediol prepolymer:

[0043] Add the succinic acid-butanediol prepolymer into a reaction kettle, displace the air with nitrogen, set the temperature at 50 °C, start stirring, gradually heat up to 175 °C and keep it warm for 1.5 hours, then cool down to 130 °C and add the lactic acid prepolymer. The molar ratio of lactic acid prepolymer to succinic acid-butanediol prepolymer is 1:9. Then add antimony trioxide as a catalyst accounting for 0.1% of the total weight of succinic acid-butanediol prepolymer and lactic acid prepolymer, triphenyl phosphate as a stabilizer accounting for 0.1% of the total weight of succinic acid-butanediol prepolymer and lactic acid prepolymer, and antioxidant 1010 accounting for 0.1% of the total weight of succinic acid-butanediol prepolymer and lactic acid prepolymer. Evacuate the air, gradually heat up to 220 °C, and keep it warm for 3 hours to obtain a lactic acid-succinic acid-butanediol ester copolymer, which is a degradable shape memory polyester copolymer.

[0044] Example 3: A preparation method of a degradable shape memory polyester copolymer is as follows:

[0045] (1) Preparation of lactic acid prepolymer:

[0046] Weigh a certain mass of lactic acid into a reaction kettle, add zinc acetate anhydrous accounting for 0.1% of the weight of lactic acid, introduce nitrogen for protection, heat up to 180 °C, start stirring, and after reacting for 3 hours, close the nitrogen and evacuate for 10 minutes to finally obtain a lactic acid prepolymer.

[0047] (2) Preparation of adipic acid-butanediol prepolymer:

[0048] Add adipic acid and 1,4-butanediol with a molar ratio of 1:1.2 into a reaction kettle, add tetrabutyl titanate as a catalyst accounting for 0.1% of the total weight of adipic acid and butanediol, evacuate the air, displace the residual air with nitrogen and continuously introduce nitrogen for protection, heat up to 200 °C, start stirring, and after reacting for 4 hours, close the nitrogen to obtain an adipic acid-butanediol prepolymer with a number-average molecular weight of 9451.

[0049] (3) Melt polymerization of lactic acid prepolymer and adipic acid-butanediol prepolymer:

[0050] Add the butanediol adipate prepolymer into a reaction kettle, displace the air with nitrogen, set the temperature at 50°C, start stirring, gradually heat up to 195°C and keep the temperature for 0.5 hour, then cool down to 150°C and add the lactic acid prepolymer. The molar ratio of the lactic acid prepolymer to the butanediol adipate prepolymer is 9:1. Then add antimony trioxide as a catalyst accounting for 0.25% of the total weight of the butanediol adipate prepolymer and the lactic acid prepolymer, triphenyl phosphate as a stabilizer accounting for 0.3% of the total weight, and antioxidant 1010 accounting for 0.3% of the total weight. Evacuate the air, gradually heat up to 180°C and keep the temperature for 7 hours to obtain the copolymer of butanediol lactate adipate, which is the degradable shape memory polyester copolymer.

[0051] Example 4: The rest is the same as Example 1, except that:

[0052] In step (1), replace lactic acid with lactide; replace zinc acetate anhydrous with tin(II) 2-ethylhexanoate to obtain the lactide prepolymer.

[0053] In step (2), replace adipic acid and butanediol with caprolactone; replace tetrabutyl titanate with tin(IV) tetraphenyl; the addition amount of tin(IV) tetraphenyl is 0.15 wt% of the weight of caprolactone to obtain the caprolactone prepolymer.

[0054] In step (3), replace the butanediol adipate prepolymer with the caprolactone prepolymer, and the molar ratio of the caprolactone prepolymer to the lactide prepolymer is 3:5; replace antimony trioxide with tetrabutyl titanate.

[0055] Example 5: The rest is the same as Example 1, except that:

[0056] In step (1), replace lactic acid with glycolide; replace zinc acetate anhydrous with tin(IV) chloride bis(butanolate) to obtain the glycolide prepolymer.

[0057] In step (2), replace adipic acid and butanediol with caprolactone; replace tetrabutyl titanate with stannous octoate; the addition amount of stannous octoate is 0.15 wt% of the weight of caprolactone to obtain the caprolactone prepolymer.

[0058] In step (3), replace the butanediol adipate prepolymer with the caprolactone prepolymer, and the molar ratio of the caprolactone prepolymer to the glycolide prepolymer is 1:4; replace antimony trioxide with tin(II) 2-ethylhexanoate.

[0059] Example 6: The rest is the same as Example 1, except that:

[0060] In step (1), replace lactic acid with methyl glycolate; replace zinc acetate anhydrous with triethoxy(tetrafluoroborate) to obtain the methyl glycolate prepolymer.

[0061] In step (3), the molar ratio of the adipic acid-butanediol prepolymer to the methyl glycolate prepolymer is 7:2; antimony trioxide is replaced by stannous octoate.

[0062] Example 7: The rest is the same as in Example 1, except that:

[0063] In step (1), lactic acid is replaced by glycolic acid; zinc acetate anhydrous is replaced by p-toluenesulfonic acid monohydrate to obtain a glycolic acid prepolymer.

[0064] In step (3), the molar ratio of the adipic acid-butanediol prepolymer to the glycolic acid prepolymer is 1:2; antimony trioxide is replaced by tetrabutyl titanate.

[0065] Example 8: The rest is the same as in Example 1, except that:

[0066] In step (1), lactic acid is replaced by glycolide.

[0067] Comparative Example 1: The rest is the same as in Example 1, except that:

[0068] In step (1), lactic acid is replaced by a mixture of glycolide and lactide with a molar ratio of 5:1.

[0069] Comparative Example 2: The rest is the same as in Example 1, except that:

[0070] In step (1), lactic acid is replaced by a mixture of glycolide and lactide with a molar ratio of 5:1.

[0071] Meanwhile, the adipic acid-butanediol prepolymer prepared in step (2) is replaced by poly(butylene adipate) with a number-average molecular weight of 2000.

[0072] Comparative Example 3: The rest is the same as in Example 1, except that:

[0073] The adipic acid-butanediol prepolymer prepared in step (2) is replaced by poly(butylene adipate) with a number-average molecular weight of 2000.

[0074] Comparative Example 4: The polymer was prepared according to the following method:

[0075] Under nitrogen protection, lactic acid, adipic acid, and 1,4-butanediol were mixed in a molar ratio of 2:1:1, and then a catalyst (composed of antimony trioxide, tetrabutyl titanate, and zinc acetate anhydrous with a weight ratio of 1:1:1) accounting for 0.5% of the total weight of lactic acid, adipic acid, and 1,4-butanediol; triphenyl phosphate accounting for 0.2% of the total weight of lactic acid, adipic acid, and 1,4-butanediol; antioxidant 1010 accounting for 0.2% of the total weight of lactic acid, adipic acid, and 1,4-butanediol were added. The mixture was evacuated, gradually heated to 200 °C, and kept warm for 5 hours to obtain the final product.

[0076] Shape Memory Performance Test of Degradable Shape Memory Polyester Copolymer

[0077] The poly(lactic acid - butylene adipate) copolymer prepared in Example 1 was made into samples. The lactic acid - butylene adipate copolymer was molded into a 0.7 - mm - thick thin sheet by a flat vulcanizing machine, and dumbbell - shaped specimens with a length of 75 mm and a middle width of 4 mm were cut by a punching machine.

[0078] The shape memory performance test was carried out on a dynamic thermomechanical analyzer

[0079] The specimen was fixed by a fixture, heated to 80 °C, and kept at a constant temperature for 1 minute. The strain at this time was marked as ε0.

[0080] A stress was applied to stretch the strain of the specimen to 100%, and the strain at this time was marked as ε1.

[0081] Keeping the strain constant, the specimen was cooled to 25 °C and kept at a constant temperature for 5 minutes.

[0082] The stress was removed, and the strain ε2 was recorded after 5 minutes.

[0083] The specimen was heated to 80 °C again and kept at a constant temperature for 30 minutes to make the specimen return to its original state and generate a residual strain ε3.

[0084] The values of the shape - fixing ratio (Rf) and the shape - recovery ratio (Rr) were calculated according to the formulas and The shape memory test curve is as Figure 1 shown. It was calculated that Rf was 97.4% and Rr was 98.0%.

[0085] Mechanical Property Test of Experimental Examples

[0086] Using the same preparation method as the shape memory performance test, specimens were made, and the tensile mechanical properties were tested on an electronic universal testing machine. At room temperature of 25 °C, the specimens were pulled to fracture at a tensile rate of 5 mm / min. The stress - strain curve is as Figure 2 shown. It can be seen that the tensile strength was 43.5 MPa and the fracture tensile strain was 535%.

[0087] For the degradation performance test, the molded specimens were subjected to corresponding degradation experiments under water, soil burial, and CALB enzyme conditions. The mass loss was weighed every week, and the mass loss rate was calculated. The results are as Figure 3 shown. The experiment was carried out for 10 weeks. It can be seen from this that the mass loss rates after 10 weeks of hydrolysis, soil burial, and enzymatic hydrolysis were 4.9%, 2.3%, and 10% respectively.

[0088] The properties of the final products prepared in Examples 2 - 8 and Comparative Examples 1 - 4 were tested according to the same test methods as above, and the results are as follows:

[0089] Table 1 Influence of Different Preparation Methods on the Shape Memory Performance and Degradation Performance of Polymers

[0090]

[0091]

[0092] As can be seen from the results in Table 1, in Comparative Example 1, when the raw materials of the hard segment prepolymer were two lactides, the shape memory performance of the polymer was poor. Also, by comparing Comparative Example 1 and 2, it can be seen that the reason for the poor performance of Comparative Example 1 may be related to the number-average molecular weight of the soft segment prepolymer. The hard segment prepolymer prepared from two lactides may rely on the soft segment prepolymer with a lower number-average molecular weight and be mismatched with the soft segment prepolymer with a higher number-average molecular weight. This incorrect matching leads to a significant reduction in both the degradability and shape memory performance of the final product. The comparison between Comparative Example 3 and Example 1 shows that the smaller the number-average molecular weight of the soft segment prepolymer, the better the degradability. Therefore, the enzymatic mass loss rate of Comparative Example 3 is greater than that of Example 1. However, the shape memory performance and strength of the final product are significantly lower than those of Example 1, indicating that choosing a soft segment prepolymer with a smaller number-average molecular weight can slightly improve the degradability but has a greater negative impact on the shape memory performance. In Comparative Example 4, the polymer was prepared by a one-pot method using the same raw materials. Due to the disordered esterification reaction between the monomers, it is difficult to form ordered and functional hard and soft segments. Therefore, the product of Comparative Example 4 does not have a shape memory function and has poor degradability.

Claims

1. A preparation method of a degradable shape memory polyester copolymer, characterized in that, It includes the following steps: (1) Using one of lactide, lactic acid, glycolide, methyl glycolate, and glycolic acid as a monomer, an esterification reaction is carried out to prepare a hard segment prepolymer; (2) Using adipic acid or succinic acid and butanediol to carry out an esterification reaction to prepare a soft segment prepolymer; or using caprolactone as a polymerization monomer to prepare a soft segment prepolymer; (3) Carrying out a melt polymerization reaction on the hard segment prepolymer and the soft segment prepolymer to obtain a degradable shape memory polyester copolymer; In step (2), the method of the esterification reaction is: adding a second catalyst to a mixture of adipic acid and butanediol or a mixture of succinic acid and butanediol, heating to 160 - 200 °C in an inert atmosphere for the esterification reaction, and obtaining a soft segment prepolymer after reacting for 4 - 8 h; The method of using caprolactone as a polymerization monomer to prepare a soft segment prepolymer is: adding a second catalyst to caprolactone, and carrying out an esterification reaction under vacuum and heating conditions to obtain a soft segment prepolymer; The molar ratio of adipic acid to butanediol is 1 - 1.2:1 - 1.2, the molar ratio of succinic acid to butanediol is 1 - 1.2:1 - 1.2, the second catalyst includes one or more of tetrabutyl titanate, tetraphenyltin, and stannous octoate, and the addition amount of the second catalyst is 0.1 - 0.25 wt% of the mixture of adipic acid and butanediol or the mixture of succinic acid and butanediol or caprolactone; In step (3), the method of the melt polymerization reaction is: in an inert atmosphere, mixing and melting the hard segment prepolymer and the soft segment prepolymer, then adding a third catalyst, triphenyl phosphate, and an antioxidant, and carrying out an esterification reaction under vacuum conditions at 180 - 220 °C for 3 - 7 h to obtain a degradable shape memory polyester copolymer; the weight ratio of the total weight of the hard segment prepolymer and the soft segment prepolymer: the third catalyst: triphenyl phosphate: antioxidant is 100:0.1 - 0.25:0.1 - 0.3:0.1 - 0.

3.

2. The preparation method of the degradable shape memory polyester copolymer according to claim 1, wherein, In step (1), the method of the esterification reaction is: mixing the monomer and 0.1 - 0.25% of the total weight of the monomer of the first catalyst, and heating to 140 - 180 °C in an inert atmosphere for the esterification reaction, and obtaining a hard segment prepolymer after reacting for 3 - 7 h.

3. The preparation method of the degradable shape memory polyester copolymer according to claim 2, characterized in that, The first catalyst includes one or more of stannous isooctoate, stannous iso - octoate, stannous oxide, stannous chloride, stannous oxalate, titanium butoxide tetrachloride, p - toluenesulfonic acid - hydrate, anhydrous zinc acetate, triethoxy tetrafluoroborate, boron trifluoride, trifluoroacetic acid, and antimony trioxide.

4. The preparation method of the degradable shape memory polyester copolymer according to claim 1, characterized in that, In step (3), the molar ratio of the hard segment prepolymer to the soft segment prepolymer is 1 - 9:1 - 9.

5. The preparation method of the degradable shape memory polyester copolymer according to claim 1, wherein The third catalyst includes one or more of antimony trioxide, tetrabutyl titanate, stannous isooctoate, and stannous octoate. The method of mixing and melting the hard segment prepolymer and the soft segment prepolymer is: first heating the soft segment prepolymer to 175 - 195 °C under stirring conditions, keeping warm for 0.5 - 1.5 h, then cooling to 130 - 150 °C and adding the hard segment prepolymer, and keeping warm until the soft segment prepolymer and the hard segment prepolymer are completely melted.

6. A method for controlling the temporary shape of a degradable shape memory polyester copolymer prepared by the preparation method according to any one of claims 1-5, characterized in that, It includes the following steps: The polyester copolymer is stretched at a temperature higher than the crystallization temperature of its soft segments and lower than the crystallization temperature of its hard segments, and then cooled to a temperature lower than the crystallization temperature of its soft segments to fix the shape after stretching.

7. The temporary shape control method of the degradable shape memory polyester copolymer according to claim 6, wherein, The crystallization temperature of the soft segments is 30 - 45 °C, and the crystallization temperature of the hard segments is 65 - 160 °C.

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