A controllable degradation dendritic polycaprolactone-based polyurethane film and its preparation method

Abstract

The present invention relates to a dendrimerized polycaprolactone-based polyurethane film with adjustable degradation and a preparation method thereof. A novel stimulus-responsive and controllable-degradation dendrimerized polycaprolactone diol is prepared through molecular design, and then it reacts with diisocyanate to synthesize a dendrimerized polymer prepolymer. Then, a chain extender is introduced to prepare the dendrimerized polycaprolactone-based polyurethane film with adjustable degradation. By introducing functionalized polycaprolactone segments into the polyurethane, the film undergoes a thermosensitive phase transition by regulating the temperature. Above the phase transition temperature, the degradation of the film is inhibited under acidic conditions, and it can degrade rapidly under alkaline conditions, enabling the polyurethane film of the present invention to effectively regulate the degradation rate under changing temperature and pH conditions, providing new ideas and approaches for the development of controllable-degradation materials. Such polyurethane films have the characteristics of temperature response and controllable degradation, can be used as temperature-responsive separation membranes, and have very broad application prospects in the field of intelligent response and degradable materials.

Description

Technical Field

[0001] The present invention relates to a degradable material and a preparation method thereof, in particular to a dendrimer polycaprolactone-based polyurethane film with controllable degradation and a preparation method thereof, which are applied to the field of degradable materials and the field of temperature-responsive intelligent material technology. Background Art

[0002] In recent years, thin film materials have been an indispensable part of industrial production and daily life. However, thin film materials have always suffered from the problems of non-degradability or too slow degradation rate, resulting in a large amount of "white" garbage. The environmental problems faced globally are becoming increasingly serious, harming surface soil and marine waters. Developing degradable materials is of great significance for environmental protection.

[0003] Polyurethane thin film materials have excellent thermal stability, chemical corrosion resistance and mechanical properties, but they are not biodegradable by themselves. As one of the degradable materials produced on a large scale in China, polycaprolactone has a special main chain structure and degradability, and is environmentally friendly. By introducing polycaprolactone polyol as the soft segment and isocyanate as the hard segment into the polyurethane material, a degradable polyurethane can be prepared. The structure and properties of polycaprolactone polyol will directly affect the use characteristics of polyurethane. (Zeng S, Wang Q, Chen P, et al. Controllable hydrolytic stability of novel fluorinated polyurethane films by incorporating fluorinated side chains[J]. Progress in Organic Coatings, 2022, 165: 106729.) At present, there is always a problem that the degradation time of the material is difficult to control. Effectively regulating the degradation of the material after use and disposal is a major challenge for current degradable materials. (Yang J D, Shu Y T, Jia H W. Novel controllable degradation behavior and biocompatibility of segmented poly–ε–caprolactone in rats[J]. Polymer Degradation and Stability, 2019, 163: 25-34.)

[0004] After modifying polycaprolactone to endow it with intelligent response behavior, it is introduced into the polyurethane film material in the form of polycaprolactone diol to effectively regulate the degradation performance. The temperature-responsive film can change the hydrophilicity and hydrophobicity of the film by adjusting the temperature, the permeation ability of the film changes, the film can maintain stability in environments with different pH values and accelerate the separation efficiency, and the film can rapidly degrade in special environments to alleviate environmental pollution problems.

[0005] Therefore, the preparation of dendritic polycaprolactone-based polyurethanes with intelligent response and controllable degradation has broad application prospects in the fields of intelligent materials and degradable films. Summary of the Invention

[0006] In order to solve the problems of the existing technology, the purpose of the present invention is to overcome the deficiencies of the existing technology, and provide a dendrimer polycaprolactone-based polyurethane film with controllable degradation and its preparation method. Novel polycaprolactone-based diols are developed, and a thin film material is constructed by combining alkoxy ether dendritic units, polycaprolactone, and polyurethane. The alkoxy ether dendritic units endow the film with thermosensitive properties, and polycaprolactone as the main chain part endows the film with degradation properties. The phase transition of the film is promoted by the temperature to regulate the hydrophilicity and hydrophobicity to change the separation effect, and the acidity and alkalinity of the pH value of the solution in which the film is located are adjusted to effectively regulate the degradation behavior of the film. The film of the present invention can be applied to the fields of intelligent response separation membranes and degradable film materials, is expected to solve the environmental pollution problems brought by non-degradable films, and provides new ways and methods for the development of novel controllable degradation materials.

[0007] In order to achieve the above invention purposes, the inventive concept adopted by the present invention is as follows:

[0008] A preparation method of a dendrimer polycaprolactone-based polyurethane film with controllable degradation, comprising the following steps:

[0009] Through the amidation reaction of a dendritic unit protected by pentafluorophenol and 4-aminocyclohexanol, and then through two oxidation reactions to obtain compound 3, and through an organocatalytic ring-opening reaction to obtain compound 4. After reacting with diisocyanate and piperazine and then preparing into a film, a dendritic polycaprolactone-based polyurethane film is obtained. The specific reaction formula of compound 4 is as follows

[0010]

[0011] Wherein R 1 is CH 3 or CH 2 CH 3 , R 2 is any compound with multiple hydroxyl groups, m = 1 to 1000, n = 1 to 1000.

[0012] According to the above inventive concept, the present invention adopts the following technical solutions:

[0013] A controllable degradable dendritic polycaprolactone polyurethane film, the structural formula of the dendritic polycaprolactone diol is:

[0014]

[0015] Where R 1 CH 3 or CH 2 CH 3 , R 2 Any polyhydroxy compound, m=1-1000, n=1-1000.

[0016] As a preferred technical solution of the present invention, a dendritic polycaprolactone polyurethane film is placed in an aqueous solution not higher than 25°C, or when the temperature of the aqueous solution is lower than the phase transition temperature of the dendritic polycaprolactone, the dendritic polycaprolactone polyurethane film is in a transparent state, and when the temperature of the aqueous solution is increased, when the temperature of the aqueous solution is higher than the phase transition temperature of the dendritic polycaprolactone, or when the temperature of the aqueous solution is not lower than 70°C, the film becomes opaque, thereby realizing the temperature response of the dendritic polycaprolactone film.

[0017] As a preferred technical solution of the present invention, the dendritic polycaprolactone polyurethane film of the present invention exhibits temperature-sensitive behavior in aqueous solution, and the phase transition temperature is 25-70°C.

[0018] As a preferred technical solution of the present invention, the degradation behavior of the dendritic polycaprolactone polyurethane film is regulated by controlling the temperature to cause the film to undergo phase transition and changing the pH acidity and alkalinity.

[0019] As a further preferred technical solution of the present invention, the degradation behavior of the dendritic polycaprolactone polyurethane film can be regulated by temperature and pH value, and the specific regulation method is as follows:

[0020] The film is placed in aqueous solutions with different pH values, and the temperature of the aqueous solution is controlled.

[0021] After the polyurethane film of the present invention absorbs water, below the phase transition temperature, the polyurethane film degrades faster under alkaline conditions than under acidic conditions. By changing the temperature to reconstruct the restricted microenvironment, above the phase transition temperature, the dendritic polycaprolactone chain segments in the film undergo dehydration collapse, the film undergoes a phase transition, and the polyurethane film has a shielding effect on hydrogen ions, so that the degradation of the polyurethane film under acidic conditions is inhibited.

[0022] As a preferred technical solution of the present invention, the dendritic polycaprolactone polyurethane film is placed in a solution with an acidic or alkaline pH value, and the temperature is adjusted to below the phase transition temperature or 20-40°C, or to above the phase transition temperature or 50-80°C, to regulate the degradation behavior of the polyurethane film.

[0023] As a preferred technical solution of the present invention, between 25 - 70 °C, the static water contact angle on the surface of the dendritic polycaprolactone-based polyurethane film is 46° - 70°.

[0024] A method for preparing a dendrimer polycaprolactone-based polyurethane film with adjustable degradation according to the present invention comprises the following steps:

[0025] a. Prepare Compound 1 by reacting aminocyclohexanol molecules with dendritic alkoxy ether-modified pentafluorophenol.

[0026] b. Perform an oxidation reaction on Compound 1 with pyridinium chlorochromate to prepare Compound 2.

[0027] c. Perform an oxidation reaction on Compound 2 with m-chloroperbenzoic acid to prepare Compound 3.

[0028] d. Perform an organocatalytic reaction on Compound 3 to prepare Compound 4.

[0029] e. React Compound 4, polytetrahydrofuran, diisocyanate and piperazine to obtain polycaprolactone-based polyurethane. Pour the mixture of the reaction products into a polytetrafluoroethylene mold, and after evacuating under reduced pressure, obtain the dendritic polycaprolactone-based polyurethane film.

[0030] As a preferred technical solution of the present invention, the method for preparing a dendrimer polycaprolactone-based polyurethane film with adjustable degradation according to the present invention is characterized in that it comprises the following steps:

[0031] a. Dissolve the dendritic alkoxy ether-modified active ester, trans-aminocyclohexanol, and N,N-diisopropylethylamine in anhydrous methanol according to a molar ratio of 1:(1 - 5):(5 - 20), react at room temperature for 12 - 24 hours, remove the solvent after the reaction, and separate and purify to obtain Compound 1 as a colorless transparent oil, and its structural formula is:

[0032]

[0033] b. Under the protection of an inert gas and in an ice bath, dissolve Compound 1 and pyridinium chlorochromate in dichloromethane according to a molar ratio of 1:(1 - 5), react at room temperature for 4 - 24 hours, remove the solvent after the reaction, and obtain a yellow-brown oil by separation, which is Compound 2, and its structural formula is:

[0034]

[0035] c. Under the protection of inert gas and in an ice bath, compound 2 and meta-chloroperoxybenzoic acid are dissolved in dichloromethane according to a molar ratio of 1:(1 - 5), and reacted at room temperature for 12 - 48 hours. After the reaction is completed, through purification, a pure product, dendritic ε-caprolactone, a colorless transparent oily substance, is obtained, which is compound 3, and its structural formula is:

[0036]

[0037] d. Under the protection of inert gas, compound 3, an initiator, and a catalyst are dissolved in tetrahydrofuran according to a molar ratio of 100:(1 - 10):(1 - 20), and reacted at room temperature for 12 - 48 hours. After the reaction is completed, dialysis is carried out using a dialysis bag (MWCO, 4000 kDa) for 3 - 5 days, and then dried to remove water, obtaining dendritic poly(ε-caprolactone), which is compound 4, and its structural formula is:

[0038]

[0039] e. Compound 4, polytetrahydrofuran, isocyanate, and chain extender piperazine are added to N,N-dimethylformamide for reaction according to a molar ratio of (1 - 4):(0 - 10):(2 - 20):(1 - 10), and 1 - 2 drops of dibutyltin dilaurate are added. After the reaction is completed, dendritic poly(ε-caprolactone)-type polyurethane is obtained; then the dendritic poly(ε-caprolactone)-type polyurethane is placed in a polytetrafluoroethylene mold, and the solvent is removed by decompression and air extraction, and finally a dendritic poly(ε-caprolactone)-based polyurethane film with adjustable degradation is obtained.

[0040] As a preferred technical solution of the present invention, in the step d, the cut-off molecular weight of the dialysis bag used is not less than 4000 kDa.

[0041] As a preferred technical solution of the present invention, in the step e, the molar ratio of the hydroxyl group in compound 4 to the isocyanate group in the isocyanate is (1 - 4):(2 - 8).

[0042] As a preferred technical solution of the present invention, in the step e, the molar ratio of compound 4 to polytetrahydrofuran is (1 - 4):(0.1 - 1).

[0043] As a preferred technical solution of the present invention, in the step e, compound 4, polytetrahydrofuran, isocyanate, and chain extender piperazine are added to N,N-dimethylformamide for reaction according to a molar ratio of (1 - 4):(0 - 10):(2 - 20):(1 - 10), and the steps are as follows:

[0044] In a polymerization tube protected by inert gas, compound 4 and polytetrahydrofuran are added and dissolved in N,N-dimethylformamide, and stirred until completely dissolved, and the solution becomes transparent;

[0045] Then, a mixed solution of diisocyanate dissolved in N, N-dimethylformamide was added. After reacting at no less than 70 °C for at least 20 min, a dendritic polycaprolactone-based polyurethane prepolymer was obtained;

[0046] Then, the entire product mixture system was cooled to room temperature, piperazine was added, 1-2 drops of dibutyltin dilaurate were added, and after reacting for at least 12 h, at least 2 drops of methanol were added to quench the reaction, obtaining a dendritic polycaprolactone-based polyurethane mixture;

[0047] Then, the dendritic polycaprolactone-based polyurethane mixture was transferred into a polytetrafluoroethylene mold, the solvent was evaporated, and after cooling to room temperature, a dendritic polycaprolactone-based polyurethane film was obtained.

[0048] Compared with the prior art, the present invention has the following outstanding advantages:

[0049] 1. The present invention introduces alkoxy ether dendritic units onto the polyurethane, making such films have good hydrophilicity;

[0050] 2. The polyurethane film of the present invention has a thermosensitive behavior in an aqueous solution, and the environmental pH value and temperature can regulate the degradation behavior of the film;

[0051] 3. The dendritic polycaprolactone-based polyurethane film with adjustable degradation prepared by the present invention can be applied to thermosensitive response separation membranes, especially in the field of intelligent response type degradable materials. Description of the Drawings

[0052] Figure 1 It is the thermosensitive phase change diagram of the dendritic polycaprolactone-based polyurethane film prepared in Example 1 of the present invention.

[0053] Figure 2 It is the schematic diagram of the static water contact angle of the dendritic polycaprolactone-based polyurethane film prepared in Example 1 of the present invention at different temperatures.

[0054] Figure 3 It is the degradation curves of the polycaprolactone-based polyurethane film prepared in Example 1 of the present invention below and above the phase transition temperature. Detailed Embodiments

[0055] In the following embodiments, a dendritic polycaprolactone-based polyurethane film with adjustable degradation, and the structural formula of the dendritic polycaprolactone diol is:

[0056]

[0057] Wherein R 1 is CH 3 or CH 2 CH 3 , R 2is a compound with any number of hydroxyl groups, where m = 1 to 1000 and n = 1 to 1000.

[0058] The above solution will be further described below in conjunction with specific implementation examples. The preferred embodiments of the present invention are described in detail as follows:

[0059] Example 1:

[0060] In this example, a method for preparing a dendrimerized polycaprolactone-based polyurethane film with controllable degradation is as follows:

[0061] a. React the dendrimerized alkoxy ether-modified active ester, trans-4-aminocyclohexanol, and N,N-diisopropylethylamine in a molar ratio of 1:1:5 in anhydrous methanol at room temperature for 12 hours. After the reaction, remove the solvent, separate and purify to obtain Compound 1 as a colorless transparent oil, and its structural formula is:

[0062]

[0063] where R 1 is CH 2 CH 3 .

[0064] b. Under the protection of an inert gas and in an ice bath, dissolve Compound 1 and pyridinium chlorochromate in a molar ratio of 1:1 in dichloromethane and react at room temperature for 4 hours. After the reaction, remove the solvent and separate to obtain a yellow-brown oil, which is Compound 2, and its structural formula is:

[0065]

[0066] where R 1 is CH 2 CH 3 .

[0067] c. Under the protection of an inert gas and in an ice bath, dissolve Compound 2 and m-chloroperoxybenzoic acid in a molar ratio of 1:1 in dichloromethane and react at room temperature for 12 hours. After the reaction, purify to obtain a pure product, a colorless transparent oil, dendrimerized caprolactone, which is Compound 3, and its structural formula is:

[0068]

[0069] where R 1 is CH 2 CH 3 .

[0070] d. Under the protection of inert gas, compound 3, initiator, and catalyst were dissolved in tetrahydrofuran according to a molar ratio of 100:10:20, and reacted at room temperature for 48 hours. After the reaction, dialysis was carried out for 3 days using a dialysis bag (MWCO, 4000 kDa), and water was removed by lyophilization to obtain dendritic polycaprolactone, which is compound 4. Its structural formula is:

[0071]

[0072] Among them, R 1 is CH 2 CH 3 , R2 is m is 10, and n is 10.

[0073] e. Compound 4, polytetrahydrofuran, diisocyanate, and chain extender piperazine were added to N,N-dimethylformamide and reacted according to a molar ratio of 4:10:20:10. The steps are as follows:

[0074] In a polymerization tube protected by inert gas, compound 4 and polytetrahydrofuran were dissolved in N,N-dimethylformamide and stirred until completely dissolved, and the solution became transparent;

[0075] Then, a mixed solution of diisocyanate dissolved in N,N-dimethylformamide was added, and after reacting at 70 °C for 20 min, a dendritic polycaprolactone-based polyurethane prepolymer was prepared;

[0076] Then, the entire product mixture system was cooled to room temperature, piperazine was added, 1 - 2 drops of dibutyltin dilaurate were added, and after reacting for 12 h, 2 drops of methanol were added to quench the reaction, obtaining a dendritic polycaprolactone-based polyurethane mixture;

[0077] The dendritic polycaprolactone-based polyurethane mixture was then transferred into a polytetrafluoroethylene mold, the solvent was evaporated, and after cooling to room temperature, a dendritic polycaprolactone-based polyurethane film was prepared.

[0078] Experimental test analysis:

[0079] The polyurethane film prepared in this example was tested to verify the thermosensitive phase transition phenomenon of the film at 25 °C and 70 °C as Figure 1 shown. When the film was placed in an aqueous solution at 25 °C, when the external temperature was lower than the phase transition temperature, the film was transparent. When the temperature of the aqueous solution was increased, when the external temperature was higher than the phase transition temperature, when the temperature was 70 °C, the film was opaque. It can be concluded that the prepared dendritic polycaprolactone-based film has good temperature response performance.

[0080] The static water contact angle of the polyurethane film prepared in this example was tested to verify the hydrophilicity and hydrophobicity of the film at 25 °C and 70 °C, as Figure 2As shown in the figure, the film was placed on a lifting table with a heating stage, and the static water contact angle of the film was measured by a high-speed camera. At 25 °C, the static water contact angle on the film surface was 46°, showing hydrophilicity. The temperature of the heating stage was gradually increased. As the temperature increased, the contact angle of the film became larger. At 70 °C, the static water contact angle was 71°, and the film became relatively hydrophobic.

[0081] The degradation experiment test was carried out on the polyurethane film prepared in this example. The film was immersed in different pH buffer aqueous solutions and placed in a sand bath at 25 °C and 70 °C for constant temperature. When the degradation time was 1, 3, 5, 7, 14, and 28 days, the samples were taken out, the residual solution on the surface was washed, placed in an oven for constant weight, and the mass change before and after degradation was measured. Each sample was measured 3 times and the average value was taken. As Figure 3 shown, the polyurethane film degraded rapidly under alkaline conditions with a pH value of 10 and acidic conditions with a pH value of 3 at 25 °C. At 70 °C, it hardly degraded under acidic conditions with a pH value of 3 and could degrade under alkaline conditions. It shows that the degradation behavior of the polyurethane film prepared in this example can be regulated by changing the temperature and pH.

[0082] Example 2:

[0083] This example is basically the same as Example 1, with the special feature that:

[0084] In this example, a preparation method of a dendrimer polycaprolactone-based polyurethane film with adjustable degradation is as follows:

[0085] a. The active ester modified with dendrimer alkoxy ether, trans-4-aminocyclohexanol, and N,N-diisopropylethylamine were dissolved in anhydrous methanol in a molar ratio of 1:5:20 and reacted at room temperature for 24 hours. After the reaction, the solvent was removed, and the compound 1 was obtained as a colorless transparent oil after separation and purification. Its structural formula is:

[0086]

[0087] where R1 is CH 3 .

[0088] b. Under the protection of inert gas and ice bath, compound 1 and pyridinium chlorochromate were dissolved in dichloromethane in a molar ratio of 1:5 and reacted at room temperature for 24 hours. After the reaction, the solvent was removed, and a yellow-brown oil was obtained after separation, which is compound 2. Its structural formula is:

[0089]

[0090] where R1 is CH 3 .

[0091] c. Under the protection of inert gas and in an ice bath, compound 2 and meta-chloroperoxybenzoic acid were dissolved in dichloromethane according to a molar ratio of 1:5, and the reaction was carried out at room temperature for 48 hours. After the reaction, it was purified to obtain a pure product, a colorless transparent oily dendritic ε-caprolactone, which is compound 3. Its structural formula is:

[0092]

[0093] where R1 is CH 3 。

[0094] d. Under the protection of inert gas, compound 3, an initiator, and a catalyst were dissolved in tetrahydrofuran according to a molar ratio of 100:1:1, and the reaction was carried out at room temperature for 12 hours. After the reaction, it was dialyzed for 3 days using a dialysis bag (MWCO, 4000 kDa), and then dehydrated by lyophilization to obtain dendritic poly(ε-caprolactone), which is compound 4. Its structural formula is:

[0095]

[0096] where R1 is CH 3 ,R2 is m is 15 and n is 15.

[0097] e. Compound 4, polytetrahydrofuran, diisocyanate, and a chain extender piperazine were added to N,N-dimethylformamide for reaction according to a molar ratio of 1:10:20:10. The steps are as follows:

[0098] In a polymerization tube protected by inert gas, compound 4 and polytetrahydrofuran were dissolved in N,N-dimethylformamide and stirred until completely dissolved, and the solution became transparent;

[0099] Then, a mixed solution of diisocyanate dissolved in N,N-dimethylformamide was added. After reacting at 70 °C for 20 min, a dendritic poly(ε-caprolactone)-based polyurethane prepolymer was prepared;

[0100] Then, the entire product mixture system was cooled to room temperature, and then piperazine was added. 1 - 2 drops of dibutyltin dilaurate were added, and after reacting for 12 h, 2 drops of methanol were added to quench the reaction to obtain a dendritic poly(ε-caprolactone)-based polyurethane mixture;

[0101] Then, the dendritic poly(ε-caprolactone)-based polyurethane mixture was transferred into a polytetrafluoroethylene mold, the solvent was evaporated, and after cooling to room temperature, a dendritic poly(ε-caprolactone)-based polyurethane film was prepared.

[0102] Compared with Example 1, the raw materials and initiators are different in this example, and dendritic polycaprolactone diols with different structures can be prepared, which are further prepared into dendritic polycaprolactone-based polyurethane films to change their hydrophilicity and hydrophobicity. The dendritic polycaprolactone-based polyurethane film in this example still has temperature-responsive behavior. Due to its stronger hydrophilicity, its degradation rate is more rapid below the phase transition temperature, while above the phase transition temperature, the degradation of the film can be inhibited under acidic conditions. By changing the temperature and pH, the degradation behavior of the polyurethane film prepared in this example can also be regulated.

[0103] Example 3:

[0104] This example is basically the same as the above examples, with the special feature that:

[0105] In this example, a method for preparing a dendritic polycaprolactone-based polyurethane film with adjustable degradation is as follows:

[0106] a. This step is the same as in Example 1;

[0107] b. This step is the same as in Example 1;

[0108] c. This step is the same as in Example 1;

[0109] d. This step is the same as in Example 1;

[0110] e. Add compound 4, diisocyanate and chain extender piperazine to N,N-dimethylformamide in a molar ratio of 4:14:10 and react. The steps are as follows:

[0111] In a polymerization tube protected by an inert gas, add compound 4 and dissolve it in N,N-dimethylformamide, stir until completely dissolved, and the solution becomes transparent;

[0112] Then add the diisocyanate mixed solution dissolved in N,N-dimethylformamide, react at 70 °C for 35 min, and obtain a dendritic polycaprolactone-based polyurethane prepolymer;

[0113] Then cool the entire product mixture system to room temperature, add piperazine, add 1 - 2 drops of dibutyltin dilaurate, react for 24 h, and then add 2 drops of methanol to quench the reaction to obtain a dendritic polycaprolactone-based polyurethane mixture;

[0114] Transfer the dendritic polycaprolactone-based polyurethane mixture to a polytetrafluoroethylene mold, evaporate the solvent, and cool to room temperature to obtain a dendritic polycaprolactone-based polyurethane film.

[0115] In this example, a method of not adding polytetrahydrofuran was used. After extending the reaction time, a dendritic polycaprolactone-based polyurethane film was prepared. By changing the content of dendritic polycaprolactone inside the film, the thermosensitive properties of the film were regulated, and thus the degradation properties were further regulated.

[0116] The degradable film in the above embodiment of the present invention, especially a dendritic polycaprolactone-based polyurethane film with controllable degradation. In the above embodiment, a novel stimulus-responsive and controllable degradation dendritic polycaprolactone diol was prepared through molecular design, and then it was reacted with diisocyanate to synthesize a dendritic polymer prepolymer, and then a chain extender was introduced to prepare a dendritic polycaprolactone-based polyurethane film with controllable degradation. By introducing functionalized polycaprolactone segments into the polyurethane, the thermosensitive phase change of the film was caused by regulating the temperature. Above the phase transition temperature, the degradation of the film was inhibited under acidic conditions, and it could degrade rapidly under alkaline conditions, enabling the polyurethane film prepared in this embodiment to effectively regulate the degradation rate under changing temperature and pH conditions, providing new ideas and approaches for the development of controllable degradation materials. Such polyurethane films have the characteristics of temperature response and controllable degradation, can be used as temperature-responsive separation membranes, and have very broad application prospects in the field of intelligent response degradable materials.

[0117] The above has described the embodiments of the present invention in conjunction with the drawings, but the present invention is not limited to the above embodiments. Various changes can also be made according to the purpose of the invention of the present invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent replacement methods. As long as they meet the invention purpose of the present invention and do not deviate from the technical principle and inventive concept of the present invention, they all belong to the protection scope of the present invention.

Claims

1. A degradable dendritic polycaprolactone polyurethane film, It is characterized in that Develop dendronized polycaprolactone diols, and construct dendronized polycaprolactone polyurethane film materials by combining alkoxy ether dendronized units, polycaprolactone, and polyurethane; the structural formula of the dendronized polycaprolactone diols is: where R 1 is CH 3 or CH 2 CH 3 , R 2 is m = 1 to 1000, n = 1 to 1000.

2. The degradable dendritic polycaprolactone polyurethane film according to claim 1, Features: When it is placed in an aqueous solution at a temperature not higher than 25°C, or when the temperature of the aqueous solution is lower than the lowest critical temperature of the dendronized polycaprolactone, the dendronized polycaprolactone polyurethane film is transparent; when the temperature of the aqueous solution is increased, when the temperature of the aqueous solution is higher than the lowest critical temperature of the dendronized polycaprolactone, or when the temperature of the aqueous solution is not lower than 70°C, the film becomes opaque, thereby achieving the temperature response of the dendronized polycaprolactone polyurethane film.

3. The degradable dendritic polycaprolactone polyurethane film according to claim 1, Features: The dendritic polycaprolactone polyurethane film is placed in a solution with an acidic or alkaline pH value, and the temperature is adjusted to below the phase transition temperature or 20-40°C, or to above the phase transition temperature or 50-80°C, to regulate the degradation behavior of the polyurethane film.

4. The degradable dendritic polycaprolactone polyurethane film according to claim 1, Features: At 25-70°C, the static water contact angle of the surface of the dendritic polycaprolactone polyurethane film is 46°-70°.

5. A method for preparing the controllable degradable dendritic polycaprolactone polyurethane film according to claim 1, It is characterized in that The steps are as follows: a. Compound 1 was prepared by reacting aminocyclohexanol molecules with pentafluorophenol modified with dendronized alkoxy ether; b. performing an oxidation reaction of compound 1 with pyridinium chlorochromate to prepare compound 2; c. oxidizing compound 2 with m-chloroperoxybenzoic acid to prepare compound 3; d. Compound 3 is subjected to an organic catalytic reaction to prepare compound 4, which is a dendronized polycaprolactone diol; e. Compound 4, polytetrahydrofuran, diisocyanate and piperazine are reacted to obtain polycaprolactone polyurethane, and the mixture of the reaction products is poured into a polytetrafluoroethylene mold, and after decompression and degassing, a dendritic polycaprolactone polyurethane film is obtained.

6. The method for preparing the controllable degradable dendritic polycaprolactone polyurethane film according to claim 5, It is characterized in that The steps are as follows: a. The dendronized alkoxy ether-modified pentafluorophenol, trans-p-aminocyclohexanol, and N,N-diisopropylethylamine are dissolved in anhydrous methanol at a molar ratio of 1:(1-5):(5-20), and the reaction is carried out at room temperature for 12-24 hours. After the reaction is completed, the solvent is removed, separated and purified to obtain compound 1 as a colorless transparent oil, whose structural formula is: wherein R 1 is CH 3 or CH 2 CH 3 ; b. Under inert gas protection and ice bath, compound 1 and pyridinium chlorochromate were dissolved in dichloromethane at a molar ratio of 1:(1-5), and reacted at room temperature for 4-24 hours. After the reaction, the solvent was removed and separated to obtain a yellow-brown oily substance, which is compound 2, having the structural formula: wherein R 1 is CH 3 or CH 2 CH 3 ; c. Under the protection of inert gas and in an ice bath, compound 2 and m-chloroperoxybenzoic acid are dissolved in dichloromethane according to a molar ratio of 1:(1 - 5), and reacted at room temperature for 12 - 48 hours. After the reaction, through purification, a pure product, colorless transparent oily dendritic ε-caprolactone, namely compound 3, is obtained, and its structural formula is: wherein R 1 is CH 3 or CH 2 CH 3 ; d. Under the protection of inert gas, compound 3, an initiator, and a catalyst are dissolved in tetrahydrofuran according to a molar ratio of 100:(1 - 10):(1 - 20), and reacted at room temperature for 12 - 48 hours. After the reaction, dialysis is carried out using a dialysis bag for 3 - 5 days, and then water is removed by lyophilization to obtain dendritic poly(ε-caprolactone), namely compound 4, which is dendritic poly(ε-caprolactone) diol, and its structural formula is: wherein R 1 is CH 3 or CH 2 CH 3 ; e. Compound 4, polytetrahydrofuran, diisocyanate, and chain extender piperazine are added to N,N-dimethylformamide for reaction according to a molar ratio of (1 - 4):(0 - 10):(2 - 20):(1 - 10). 1 - 2 drops of dibutyltin dilaurate are added. After the reaction is completed, dendritic poly(ε-caprolactone)-type polyurethane is obtained; then the dendritic poly(ε-caprolactone)-type polyurethane is placed in a polytetrafluoroethylene mold, and the solvent is removed by decompression and air extraction, and finally a dendrimerized poly(ε-caprolactone)-type polyurethane film with adjustable degradation is obtained.

7. The preparation method of the dendrimerized poly(ε-caprolactone)-type polyurethane film with adjustable degradation according to claim 6, characterized in that: In the step d, the cut-off molecular weight of the dialysis bag used is not less than 4000 kDa.

8. The preparation method of the dendrimerized poly(ε-caprolactone)-type polyurethane film with adjustable degradation according to claim 5, characterized in that: In the step e, the molar ratio of the hydroxyl group in compound 4 to the isocyanate group in diisocyanate is (1 - 4):(2 - 8).

9. The preparation method of the dendrimerized poly(ε-caprolactone)-type polyurethane film with adjustable degradation according to claim 5, characterized in that: In the step e, the molar ratio of compound 4 to polytetrahydrofuran is (1 - 4):(0.1 - 1).

10. The preparation method of the dendrimerized poly(ε-caprolactone)-type polyurethane film with adjustable degradation according to claim 5, characterized in that: In the step e, compound 4, polytetrahydrofuran, diisocyanate, and chain extender piperazine are added to N,N-dimethylformamide for reaction according to a molar ratio of (1 - 4):(0 - 10):(2 - 20):(1 - 10), and the steps are as follows: In a polymerization tube protected by inert gas, compound 4 and polytetrahydrofuran are added and dissolved in N,N-dimethylformamide, and stirred until completely dissolved, and the solution becomes transparent; Then a mixed solution of diisocyanate dissolved in N,N-dimethylformamide is added, and the reaction is carried out at a temperature not lower than 70 °C for at least 20 min to obtain a dendritic poly(ε-caprolactone)-type polyurethane prepolymer; Then the entire product mixture system is cooled to room temperature, and then piperazine is added, 1 - 2 drops of dibutyltin dilaurate are added, and the reaction is carried out for at least 12 h, and then at least 2 drops of methanol are added to quench the reaction to obtain a dendritic poly(ε-caprolactone)-type polyurethane mixture; Then transfer the dendritic polycaprolactone-based polyurethane mixture into a polytetrafluoroethylene mold, evaporate the solvent, and after cooling to room temperature, a dendritic polycaprolactone-based polyurethane film is obtained.

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