A polycaprolactone-based functional polyurethane material, a preparation method and applications thereof

Abstract

The application discloses a polyurethane material with shape memory function and double degradation, a preparation method and application thereof, and belongs to the field of functional polyurethane materials. The polyurethane material preparation method and process are as follows: isosorbide and polycaprolactone diol are mixed under a nitrogen atmosphere, then diisocyanate monomer is added and reacted for 9-12 hours, finally a chain extender hydroxyethyl hexahydro-s-triazine is added, after stirring for 30 minutes, the reaction mixture is poured into a polytetrafluoroethylene mold, and a polyurethane film is prepared by solidification at 80 DEG C. By finely adjusting the proportion of isosorbide rigid structural units and hexahydro-s-triazine crosslinking structural units, a double degradation polyurethane with chemical degradation and biodegradation is obtained. The polyurethane prepared by the application also has good mechanical properties and biocompatibility, and exhibits good shape memory function, shape fixation rate (R f ) and shape recovery rate (R r ) are greater than 90%.

Description

Technical Field

[0001] This invention relates to the field of functional polyurethane materials, specifically to a polycaprolactone-based multifunctional polyurethane material that integrates biocompatibility, shape memory function, and dual degradability, its preparation method, and its applications. Background Technology

[0002] Due to its excellent mechanical properties, performance adjustability, and low overall cost, polyurethane is widely used in many fields. However, discarded polyurethane products persist in the environment for a long time, causing serious damage to the environment and ecosystems.

[0003] To address the environmental and ecological problems caused by polyurethane materials and their sustainability, researchers have explored the introduction of biodegradable structures and biomass resources into polyurethane material preparation over the past few decades. For example, using bio-based green polyols to prepare polyurethane products is one effective means of alleviating the resource crisis. However, polyurethane materials prepared solely by replacing petroleum-based raw materials with biomass, especially cross-linked polyurethane materials, still suffer from low degradation rates and incomplete degradation.

[0004] Due to the irreversible cross-linked structure of thermosetting materials, high temperatures, special solvents, or strong oxidants are typically required to break the chemical bonds, posing significant challenges to their rapid degradation and efficient recycling. The key to overcoming this challenge lies in synthesizing polyurethanes containing reversible dynamic covalent structures. These reversible dynamic covalent bonds mainly include ester bonds (OC=O), acetal bonds (-O-CH(CH3)-O-), disulfide bonds (-SS-), imine bonds (-C=N-), and hexahydrotriazine (hydroxyethyl hexahydrotriazine), among others. These groups can decompose under relatively mild conditions. The hexahydrotriazine structure is an acid-sensitive six-membered heterocycle; its derivatives can decompose into amines and formaldehyde when exposed to acidic solutions. Introducing it into thermosetting materials can fundamentally solve the scientific and technological challenges of the difficult degradation and recycling of these materials.

[0005] Introducing biodegradable structures and biomass resources into polyurethane materials simultaneously can fundamentally address the environmental and ecological problems and sustainability issues caused by polyurethane materials. Patent "A Quercetin-Based Biodegradable Thermosetting Polyurethane and Its Preparation Method" (ZL 202210983423.4) discloses an acid-hydrolyzable polyurethane material based on the biomass raw materials quercetin and hydroxyethyl hexahydrotriazine, and its preparation method. Patent "A Bio-Based Flame-Retardant Thermoplastic Polyurethane Material and Its Preparation Method" (CN202210889262.2) discloses a flame-retardant polyurethane material with high biomass content and its preparation method, but does not mention the degradation rate. Novel polyurethane materials that combine degradability and functionality represent a trend in sustainable materials development. Currently, research in this field is receiving widespread attention, but continuous exploration is still needed in how to construct high-performance polyurethane materials with dual degradability (biodegradability, chemical degradability, etc.) and other special functions. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a polycaprolactone-based functional polyurethane material, its preparation method, and its applications. This invention proposes introducing two biodegradable structures, hexahydrotriazine and polyester polyol, into the preparation of isosorbide-based polyurethane materials, thereby endowing the polyurethane with multiple chemical and biological degradation properties. Secondly, the biomass raw material isosorbide is inexpensive, readily available, renewable, and environmentally friendly, improving various aspects of the material's properties. To meet the requirements of biomedical applications, the polyurethane material prepared using a non-catalytic system and polyester polyol exhibits good biocompatibility and shape memory properties, and is expected to be used in medical materials and as a matrix material for flexible sensors.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0008] A polycaprolactone (PCL)-based functional polyurethane material contains two types of reversible dynamic covalent bonds: an ester group and a hexahydrotriazine ring. Its strength and toughness are controlled by the ratio of isosorbide rigid structure raw materials and hydroxyethyl hexahydrotriazine crosslinking structure raw materials. The synthesis reaction process is as follows.

[0009]

[0010] This invention also provides a method for preparing a polycaprolactone (PCL)-based functional polyurethane material, comprising the following steps:

[0011] (1) Isosorbide and hydroxyl-terminated polycaprolactone polyol were added to a reaction vessel under a nitrogen atmosphere and stirred and mixed evenly in a molten state. Then, diisocyanate monomer dissolved in an organic solvent was added to prepolymerize and obtain -NCO-terminated polyurethane prepolymer.

[0012] (2) Continue to add hydroxyethyl hexahydrotriazine to the polymerization system in step (1), stir the reaction continuously, then pour the reaction solution into a polytetrafluoroethylene mold to level it, put it in a vacuum oven to evaporate the solvent and cure it completely to obtain a polyurethane film.

[0013] Further, the organic solvent mentioned in step (1) includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0014] Furthermore, in step (1), the molar ratio of isosorbide to polycaprolactone diol is 4:2, 3:2, 2:2, 1:2 or 0:2.

[0015] Furthermore, in step (1), the stirring temperature is 60℃ and the time is 40min; the diisocyanate monomer is added and reacted for 9-12h at a reaction temperature of 120℃.

[0016] Further, the diisocyanate mentioned in step (1) includes one or more of hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and isoflurone diisocyanate.

[0017] Further, the prepolymer was obtained as an -NCO-terminated polyurethane prepolymer, which was then cooled to 60°C.

[0018] Furthermore, in step (2), the continuous stirring reaction time is 30 min and the reaction temperature is 60℃.

[0019] Furthermore, in step (2), the molar ratio of isosorbide to hydroxyethyl hexahydrotriazine is 4:0, 3:1, 2:2, 1:3 or 0:4.

[0020] Furthermore, in step (2), the product is placed in a vacuum oven for drying for 20 hours at a temperature of 80°C.

[0021] Compared with the prior art, the present invention exhibits many significant advantages, specifically in the following aspects:

[0022] (1) The polyurethane material of this invention represents a significant advancement in terms of mechanical and heat resistance properties. This material not only possesses excellent tensile strength, elongation at break, and abrasion resistance, maintaining structural stability and integrity under various complex environments, but its heat resistance also far surpasses that of traditional polyurethane materials. Even at high temperatures, it maintains good physical properties and is not prone to deformation or failure. Therefore, this polyurethane material is highly suitable for use as a matrix material in medical materials and flexible sensors that require extremely high mechanical and heat resistance properties, such as pacemaker housings, artificial blood vessels, and wearable health monitoring devices, providing a more reliable and durable material option for the medical field.

[0023] (2) Biocompatibility is one of the important indicators for evaluating the quality of medical materials. The polyurethane material of this invention exhibits excellent biocompatibility, with cell activity on its film surface reaching as high as 88% in a 72-hour experiment. This data fully demonstrates the material's promoting effect on cell growth and proliferation, reducing the risk of immune or rejection reactions after implantation. Therefore, this polyurethane material has broad application prospects in the biomedical field, such as as a tissue engineering scaffold, wound dressing, and drug controlled-release carrier, which can significantly improve treatment efficacy and patient comfort.

[0024] (3) Shape memory function is an important property of polyurethane materials and is crucial for certain specific applications. The polyurethane material of this invention exhibits excellent shape memory function, with a shape retention rate (Ri) of [missing information]. f ) and shape recovery rate (R r The yield rate (FYR) is greater than 90%, meaning that the material can quickly and accurately recover its original shape after being deformed by external forces. This characteristic makes the material have great application potential in fields such as smart wearable devices, adaptive structures, and soft robots, and can provide users with a more personalized and intelligent user experience.

[0025] (4) In terms of degradation performance, the polyurethane material of this invention also exhibits unique advantages. Compared with traditional polyurethane materials, this material has both good chemical and biodegradability. Under dilute acid conditions, it can degrade rapidly and completely, facilitating material recycling and environmentally friendly utilization. Simultaneously, after being placed in a biological enzyme buffer for 6 weeks, the material also undergoes significant degradation, indicating that it has good degradation performance in vivo, reducing environmental pollution and potential harm to organisms. This characteristic makes the material have broader application prospects in the biomedical field, such as as a biodegradable implant, drug carrier, and tissue engineering material, better meeting the medical field's needs for environmental protection, safety, and efficiency. Attached Figure Description

[0026] Figure 1 The ATR-FTIR spectra of polyurethane films prepared by different molar ratios of isosorbide and hydroxyethyl hexahydrotriazine in Examples 1-5 are shown.

[0027] Figure 2 The stress-strain curves of the polyurethane films in Examples 1-5 are shown (the embedded image is a digital image of PCL-PU2 in Example 2 lifting an object weighing approximately 20,000 times its own weight).

[0028] Figure 3 This is a diagram illustrating the shape memory process of a polyurethane film (PCL-PU2 in Example 2).

[0029] Figure 4 Fluorescence micrographs of L929 cells cultured on a polyurethane film (PCL-PU2 in Example 2) for 24h, 48h, and 72h.

[0030] Figure 5 The images show SEM images of the polyurethane films prepared in Examples 1-5 before and after 6 weeks of biodegradation.

[0031] Figure 6 The degradation phenomena of the polyurethane series films prepared in Examples 1-5 in 2 mol / L phosphoric acid / ethanol solution are shown.

[0032] In the figure, PCL-PU1, PCL-PU2, PCL-PU3, PCL-PU4, and PCL-PU5 correspond to the polyurethane series films prepared in Examples 1, 2, 3, 4, and 5, respectively. Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0034] In an embodiment of the present invention, a method for preparing a polycaprolactone-based functional polyurethane material includes the following steps:

[0035] (1) Isosorbide and hydroxyl-terminated polycaprolactone polyol were added to a reaction vessel under a nitrogen atmosphere and stirred and mixed evenly in a molten state. Then, diisocyanate monomer dissolved in an organic solvent was added to prepolymerize and obtain -NCO-terminated polyurethane prepolymer.

[0036] (2) Continue to add hydroxyethyl hexahydrotriazine to the polymerization system in step (1), stir the reaction continuously, then pour the reaction solution into a polytetrafluoroethylene mold to level it, put it in a vacuum oven to evaporate the solvent and cure it completely to obtain a polyurethane film.

[0037] The organic solvent mentioned in step (1) includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0038] In step (1), the molar ratio of isosorbide to polycaprolactone diol is 4:2, 3:2, 2:2, 1:2 or 0:2.

[0039] In step (1), the stirring temperature is 60℃ and the time is 40min; the diisocyanate monomer is added and reacted for 9-12h at a reaction temperature of 120℃.

[0040] The diisocyanate mentioned in step (1) includes one or more of hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and isoflurone diisocyanate.

[0041] In step (1), a -NCO-terminated polyurethane prepolymer is obtained by prepolymerization, and then cooled to 60°C.

[0042] In step (2), the reaction time is 30 min and the reaction temperature is 60℃.

[0043] In step (2), the molar ratio of isosorbide to hydroxyethyl hexahydrotriazine is 4:0, 3:1, 2:2, 1:3 or 0:4.

[0044] In step (2), the product is placed in a vacuum oven for drying for 20 hours at a temperature of 80°C.

[0045] Technical principle of the invention:

[0046] This invention presents an innovative method for preparing polycaprolactone (PCL)-based functional polyurethane materials. Its ingenuity lies in the precise control of raw material quantities and meticulous optimization of process parameters at each step. This not only ensures superior material performance but also achieves high efficiency and stability in the preparation process. The following is an in-depth analysis of the preparation method of this invention, emphasizing the necessity of controlling raw material quantities and the sequence of steps, as well as the importance of optimizing process parameters.

[0047] 1. The necessity and importance of controlling the amount of raw materials used

[0048] (1) Selection of diisocyanates: Different types of diisocyanates (such as hexamethylene diisocyanate, toluene diisocyanate, etc.) give polyurethane materials different chemical structures and physical properties. By selecting or mixing these monomers, the hardness, elasticity, heat resistance and chemical corrosion resistance of the material can be precisely controlled.

[0049] (2) Amount of hydroxyethyl hexahydrotriazine added: As a chain extender, the addition of hydroxyethyl hexahydrotriazine not only promotes the elongation of polyurethane chains, but also introduces additional functional groups, enhancing the crosslinking degree and thermal stability of the material. Adjusting its ratio with isosorbide can finely control the crosslinking density of the material, thereby affecting key performance indicators such as the elastic modulus, tensile strength and elongation at break of the material.

[0050] 2. The necessity that the order of steps cannot be changed

[0051] In the preparation process, the order of each step is carefully designed and cannot be arbitrarily changed. First, the mixing of isosorbide and polycaprolactone diol in the molten state ensures sufficient contact and uniform distribution between their molecules, laying a good foundation for subsequent chemical reactions. Next, diisocyanate monomers dissolved in organic solvents are added for prepolymerization. This step needs to be carried out under specific temperature and time conditions to ensure the formation of -NCO-terminated polyurethane prepolymer. Adding hydroxyethyl hexahydrotriazine prematurely may interfere with the prepolymerization reaction, leading to a decrease in material properties. Therefore, strictly adhering to the sequence of steps is crucial to ensuring material quality.

[0052] 3. The necessity and technical benefits of optimizing process parameters

[0053] (1) Stirring temperature and time: During the melt mixing and prepolymerization stages, appropriate stirring temperature and time can accelerate the reaction process and promote the full reaction between raw materials. For example, a stirring temperature of 60℃ and a mixing time of 40 min ensure the uniform dispersion of raw materials, providing good conditions for subsequent reactions. The prepolymerization reaction is carried out at 120℃ for 9-12 h, which ensures the full formation of -NCO-terminated prepolymers and guarantees the performance of the final material.

[0054] (2) Drying conditions in a vacuum oven: After pouring the reaction solution into the mold, solvent evaporation and curing are carried out in a vacuum oven, which is a key step in preparing high-quality polyurethane films. A temperature of 80℃ and a drying time of 20h ensure effective removal of the solvent and avoid material degradation caused by high temperature, thus ensuring the flatness and structural integrity of the film.

[0055] In summary, through this series of precisely controlled steps and optimized process parameters, this invention not only successfully prepared PCL-based functional polyurethane materials with excellent properties but also achieved unexpected technical effects, such as improved biocompatibility, mechanical strength, and thermal stability, broadening its application prospects in multiple fields such as biomedicine, aerospace, and automotive manufacturing. The innovation and practicality of this preparation method undoubtedly open up new directions for the research and development of PCL-based polyurethane materials.

[0056] To make the present invention more fully disclosed, more specific embodiments are described below.

[0057] Example 1

[0058] 4 g of hydroxyl-terminated polycaprolactone (2000 molecular weight, 2 mmol) and 0.45 g of isosorbide (3 mmol) were added to a three-necked flask. The mixture was heated to 60 °C and stirred for 40 min. 1.22 g of hexamethylene diisocyanate (7.2 mmol) was dissolved in 3 mL of N,N-dimethylformamide (DMF) and added to the reaction system. The temperature was raised to 120 °C and the reaction was continued for 10 h to form a prepolymer. A measured amount of DMF was added to control the viscosity of the reaction system. 0.10 g of hydroxyethyl hexahydrotriazine (0.44 mmol) was added to the prepolymer to carry out a chain extension reaction. After reacting for 30 min, the reaction solution was poured into a polytetrafluoroethylene mold and dried at 80 °C for 20 h to obtain a polycaprolactone-based multifunctional polyurethane material (denoted as PCL-PU1) that integrates biocompatibility, shape memory function, and dual degradability.

[0059] The 72-hour cell viability of L929 mouse fibroblasts on this polyurethane surface was 87.76%; the tensile strength of this polyurethane was 26.2 MPa, and the elongation at break was 967%; the shape fixation rate (R) of this polyurethane was [missing information]. f ) and shape recovery rate (R r The percentages were 96.50% and 92.48%, respectively; the polyurethane was completely degraded in 2 mol / L phosphoric acid / ethanol solution in 20 h, and lost 11.8% of its weight in 1 mg / mL lipase PBS buffer.

[0060] Example 2

[0061] In a 100 ml three-necked flask, 4 g of hydroxyl-terminated polycaprolactone (2000 molecular weight, 2 mmol) and 0.30 g of isosorbide (2 mmol) were added. The mixture was heated to 60 °C and stirred for 40 min. 1.22 g of hexamethylene diisocyanate (7.2 mmol) was dissolved in 3 mL of N,N-dimethylformamide (DMF) and added to the reaction system. The temperature was raised to 120 °C and the reaction was continued for 10 h to form a prepolymer. A measured amount of DMF was added to control the viscosity of the reaction system. 0.30 g of hydroxyethyl hexahydrotriazine (1.33 mmol) was added to the prepolymer to carry out a chain extension reaction. After reacting for 30 min, the reaction solution was poured into a polytetrafluoroethylene mold and dried at 80 °C for 20 h to obtain a polycaprolactone-based multifunctional polyurethane material (denoted as PCL-PU2) that integrates biocompatibility, shape memory function, and dual degradability.

[0062] The 72-hour cell viability of L929 mouse fibroblasts on this polyurethane surface was 88.69%; the tensile strength of this polyurethane was 31.4 MPa, and the elongation at break was 737%; the shape fixation rate (R) of this polyurethane was [missing information]. f) and shape recovery rate (R r The percentages were 96.30% and 92.59%, respectively; the polyurethane was completely degraded in 2.5 h in 2 mol / L phosphoric acid / ethanol solution and lost 15.3% of its weight in 1 mg / mL lipase PBS buffer.

[0063] Example 3

[0064] 4 g of hydroxyl-terminated polycaprolactone (2000 molecular weight, 2 mmol) and 0.15 g of isosorbide (1 mmol) were added to a three-necked flask. The mixture was heated to 60 °C and stirred for 40 min. 1.22 g of hexamethylene diisocyanate (7.2 mmol) was dissolved in 3 mL of N,N-dimethylacetamide (DMAc) and added to the reaction system. The temperature was raised to 120 °C and the reaction was continued for 10 h to form a prepolymer. A measured amount of DMAc was added to control the viscosity of the reaction system. 0.46 g of hydroxyethyl hexahydrotriazine (2 mmol) was added to the prepolymer to carry out a chain extension reaction. After reacting for 30 min, the reaction solution was poured into a polytetrafluoroethylene mold and dried at 80 °C for 20 h to obtain a polycaprolactone-based multifunctional polyurethane material (denoted as PCL-PU3) that integrates biocompatibility, shape memory function, and dual degradability.

[0065] The 72-hour cell viability of L929 mouse fibroblasts on this polyurethane surface was 87.54%; the tensile strength of this polyurethane was 14.3 MPa, and the elongation at break was 617%; the shape fixation rate (R) of this polyurethane was [missing information]. f ) and shape recovery rate (R r The percentages were 96.37% and 92.35%, respectively; the polyurethane was completely degraded in 2 mol / L phosphoric acid / ethanol solution in 1.8 h and lost 16.4% of its weight in 1 mg / mL lipase PBS buffer.

[0066] Example 4

[0067] 4g of hydroxyl-terminated polycaprolactone (2000 molecular weight, 2 mmol) was added to a three-necked flask, heated to 60°C, and stirred for 40 min. 1.22g of hexamethylene diisocyanate (7.2 mmol) was dissolved in 3mL of N,N-dimethylformamide (DMF) and added to the reaction system. The temperature was raised to 120°C, and the reaction was continued for 10 h to form a prepolymer. A measured amount of DMF was added to control the viscosity of the reaction system. 0.61g of hydroxyethyl hexahydrotriazine (2.67 mmol) was added to the prepolymer for chain extension. After reacting for 30 min, the reaction solution was poured into a polytetrafluoroethylene mold and dried at 80°C for 20 h to obtain a polycaprolactone-based multifunctional polyurethane material (denoted as PCL-PU4) that integrates biocompatibility, shape memory function, and dual degradability.

[0068] The 72-hour cell viability of L929 mouse fibroblasts on this polyurethane surface was 88.32%; the tensile strength of this polyurethane was 15.3 MPa, and the elongation at break was 557%; the shape fixation rate (R) of this polyurethane was [not specified]. f ) and shape recovery rate (R r The percentages were 95.85% and 92.43%, respectively; the polyurethane was completely degraded in 7.5 h in 2 mol / L phosphoric acid / ethanol solution and lost 28.8% of its weight in 1 mg / mL lipase PBS buffer.

[0069] Example 5

[0070] In a three-necked flask, 4 g of hydroxyl-terminated polycaprolactone (2000 molecular weight, 2 mmol) and 0.60 g of isosorbide (4 mmol) were added. The mixture was heated to 60°C and stirred for 40 min. 1.22 g of hexamethylene diisocyanate (7.2 mmol) was dissolved in 3 mL of N,N-dimethylformamide (DMF) and added to the reaction system. The temperature was raised to 80°C, and the reaction was continued for 12 h to form a prepolymer. A measured amount of DMF was added to control the viscosity of the reaction system. Without adding hydroxyethyl hexahydrotriazine, the above reaction solution was directly poured into a polytetrafluoroethylene mold and dried at 80°C for 20 h to obtain a polycaprolactone-based multifunctional polyurethane material (denoted as PCL-PU5) that integrates biocompatibility, shape memory function, and dual degradability.

[0071] The 72-hour cell viability of L929 mouse fibroblasts on this polyurethane surface was 88.13%; the tensile strength of this polyurethane was 13.5 MPa, and the elongation at break was 766%; the shape fixation rate (R) of this polyurethane was [missing information]. f ) and shape recovery rate (R rThe percentages were 96.14% and 92.87%, respectively; the polyurethane was completely degraded in 2 mol / L phosphoric acid / ethanol solution in 48 h, and lost 2.7% of its weight in 1 mg / mL lipase PBS buffer.

[0072] Example 6

[0073] In a three-necked flask, 4 g of hydroxyl-terminated polycaprolactone (2000 molecular weight, 2 mmol) and 0.30 g of isosorbide (2 mmol) were added. The mixture was heated to 60 °C and stirred for 40 min. 1.25 g of toluene diisocyanate (7.2 mmol) was dissolved in 3 mL of N,N-dimethylacetamide (DMAc) and added to the reaction system. The temperature was raised to 120 °C and the reaction was continued for 12 h to form a prepolymer. A measured amount of DMF was added to control the viscosity of the reaction system. 0.30 g of hydroxyethyl hexahydrotriazine (1.33 mmol) was added to the prepolymer to carry out a chain extension reaction. After reacting for 30 min, the reaction solution was poured into a polytetrafluoroethylene mold and dried at 80 °C for 20 h to obtain a polycaprolactone-based multifunctional polyurethane material (denoted as PCL-PU6) that integrates biocompatibility, shape memory function, and dual degradability.

[0074] The 72-hour cell viability of L929 mouse fibroblasts on this polyurethane surface was 86.67%; the tensile strength of this polyurethane was 33.6 MPa, and the elongation at break was 569%; the shape fixation rate (R) of this polyurethane was [missing information]. f ) and shape recovery rate (R r The percentages were 94.45% and 90.76%, respectively; the polyurethane was completely degraded in 2 mol / L phosphoric acid / ethanol solution in 4.5 h, and lost 13.7% of its weight in 1 mg / mL lipase PBS buffer.

[0075] Example 7

[0076] In a three-necked flask, 4 g of hydroxyl-terminated polycaprolactone (2000 molecular weight, 2 mmol) and 0.30 g of isosorbide (2 mmol) were added. The mixture was heated to 60°C and stirred for 40 min. 1.80 g of diphenylmethane diisocyanate (7.2 mmol) was dissolved in 3 mL of N-methylpyrrolidone (NMP) and added to the reaction system. The temperature was raised to 120°C and the reaction was continued for 10 h to form a prepolymer. A measured amount of DMF was added to control the viscosity of the reaction system. 0.30 g of hydroxyethyl hexahydrotriazine (1.33 mmol) was added to the prepolymer for chain extension. After reacting for 30 min, the reaction solution was poured into a polytetrafluoroethylene mold and dried at 80°C for 20 h to obtain a polycaprolactone-based multifunctional polyurethane material (denoted as PCL-PU7) that integrates biocompatibility, shape memory function, and dual degradability.

[0077] The 72-hour cell viability of L929 mouse fibroblasts on this polyurethane surface was 88.15%; the tensile strength of this polyurethane was 34.8 MPa, and the elongation at break was 541%; the shape fixation rate (R) of this polyurethane was [missing information]. f ) and shape recovery rate (R r The percentages were 93.83% and 90.22%, respectively; the polyurethane was completely degraded in 5 h in 2 mol / L phosphoric acid / ethanol solution, and lost 13.3% of its weight in 1 mg / mL lipase PBS buffer.

[0078] Example 8

[0079] In a three-necked flask, 4 g of hydroxyl-terminated polycaprolactone (2000 molecular weight, 2 mmol) and 0.30 g of isosorbide (2 mmol) were added. The mixture was heated to 60 °C and stirred for 40 min. 1.60 g of isoflurane diisocyanate (7.2 mmol) was dissolved in 3 mL of N,N-dimethylformamide (DMF) and added to the reaction system. The temperature was raised to 120 °C and the reaction was continued for 9 h to form a prepolymer. A measured amount of DMF was added to control the viscosity of the reaction system. 0.30 g of hydroxyethyl hexahydrotriazine (1.33 mmol) was added to the prepolymer for chain extension. After reacting for 30 min, the reaction solution was poured into a polytetrafluoroethylene mold and dried at 80 °C for 20 h to obtain a polycaprolactone-based multifunctional polyurethane material (denoted as PCL-PU8) that integrates biocompatibility, shape memory function, and dual degradability.

[0080] The 72-hour cell viability of L929 mouse fibroblasts on this polyurethane surface was 87.85%; the tensile strength of this polyurethane was 33.1 MPa, and the elongation at break was 635%; the shape fixation rate (R) of this polyurethane was [not specified]. f) and shape recovery rate (R r The percentages were 95.13% and 91.47%, respectively; the polyurethane was completely degraded in 3.5 h in 2 mol / L phosphoric acid / ethanol solution and lost 14.1% of its weight in 1 mg / mL lipase PBS buffer.

[0081] The performance test results of the polyurethane samples in the above examples show that the isosorbide-based polyurethanes prepared based on the polycaprolactone and hexahydrotriazine structures all exhibit high mechanical strength, good shape memory function, and dual degradation properties of complete acid hydrolysis and biodegradation. Furthermore, Examples 1-5 demonstrate that by adjusting the ratio of rigid and cross-linked raw materials in the polyurethane structure, the strength, toughness, and biodegradability of the material can be adjusted. Comparing Examples 2 and 6-8, it can be seen that changing the diisocyanate structure, i.e., increasing the rigidity of the polyurethane hardness structure, helps to improve the mechanical strength of the polyurethane.

[0082] The following is an appendix Figure 1-6 This further illustrates the structure and properties of the polyurethane samples in Examples 1-5.

[0083] See Figure 1 The polyurethane films prepared from different molar ratios of isosorbide and hydroxyethyl hexahydrotriazine in Examples 1-5 were characterized by FTIR. First, hexamethylene diisocyanate (HDI) showed a distinct isocyanate characteristic absorption peak, while the -NCO characteristic absorption peak completely disappeared in the infrared spectrum of the polyurethane films, indicating that the excess isocyanate groups had been completely consumed, demonstrating a complete polycondensation reaction. Second, the hydroxyl peaks of isosorbide, hydroxyethyl hexahydrotriazine, and polycaprolactone (PCL) in the reactants were completely reacted. The infrared characteristic absorption peaks of the polyurethane films showed consistent elution positions, indicating that the synthesized polyurethanes have similar structures.

[0084] See Figure 2 The mechanical properties of the polyurethane films from Examples 1-5 were tested. As shown in the figure, the tensile strength of the samples initially increased and then decreased with increasing hexahydrotriazine content. Compared to polyurethane without hexahydrotriazine, the tensile strength of polyurethane with hexahydrotriazine was significantly improved. However, with further increases in hexahydrotriazine content, the tensile strength of the material reached a threshold, and the crosslinking density essentially reached saturation. Excessive hexahydrotriazine led to a decrease in tensile strength. Furthermore, the reduction in isosorbide in the system, and the lack of rigid groups that reinforce the material, also easily resulted in a decrease in mechanical properties. Overall, the polyurethane film PCL-PU2 prepared in Example 2 exhibited better mechanical properties (tensile strength of 31.13 MPa and elongation at break of 736.33%).

[0085] See Figure 3 The polyurethane film PCL-PU2 prepared in Example 2 was cut into dumbbell-shaped strips. The strips were heated to 37°C, where the crystalline regions of the polyurethane film were in a molten state, exhibiting good molecular chain fluidity. After softening, the strips were stretched to 200%. Next, the strips were held at -5°C for 5 minutes to fix the temporary shape. After being left at room temperature for 30 minutes, the material was found to maintain its shape well. This is because the soft segments crystallize under stress and low temperature, fixing the stress within the material and preventing molecular chain movement, thus fixing the material to a temporary shape. Heating the sample to 37°C accelerates the movement of the molecular chains, and the melting of the soft segment crystals leads to the release of internal stress, allowing the material to essentially return to its initial shape. Based on the shape fixation rate (R... f ) and shape recovery rate (R r The R value of the polyurethane film prepared in Example 2 was calculated using the formula. f and R r The figures were 96.30% and 92.59%, respectively.

[0086] See Figure 4 The images show fluorescence microscopy images of L929 mouse fibroblasts cultured on the polyurethane film PCL-PU2 material prepared in Example 2 for 24h, 48h, and 72h. As can be seen, Calcein-AM, a live cell staining agent, easily penetrates the cell membrane. Once inside the cytoplasm, esterases hydrolyze it into Calcein, which remains inside the cell and emits strong green fluorescence. At all three time points, the cells spread well and are well-distributed on the polyurethane film surface. The cells are morphologically healthy, with clear and intact edges, and are spindle-shaped. These results indicate that the material surface is suitable for cell growth and has excellent biocompatibility.

[0087] See Figure 5 The images show SEM images of the polyurethane films prepared in Examples 1-5 at 0 and 6 weeks of degradation. It can be seen that the sample surface was smooth and flat before degradation. With the increase of hydroxyethyl hexahydrotriazine, the surface of the degraded sample became rougher, and even obvious cracks appeared. As mentioned earlier, the degradation rate of the film gradually increased due to the acidic carboxyl group autocatalytic reaction. The surface of polyurethane film PCL-PU1 was relatively rough, while the surface of polyurethane film PCL-PU4 had obvious grooves and voids, indicating a more severe degradation. The changes in film surface morphology and the macroscopic mass loss are consistent.

[0088] See Figure 6Five polyurethane films with different proportions were placed in a 2 mol / L phosphoric acid-ethanol solution for degradation experiments. It was found that the polyurethane film PCL-PU5 prepared in Example 5 had the longest degradation time. This is because this film does not contain a hydroxyethyl hexahydrotriazine ring, resulting in a longer degradation time in a slightly acidic solution. However, as a thermoplastic polyurethane material, its molecules are essentially linear and soluble, thus it can be completely degraded. The degradation time of the other proportions of films decreased with increasing hydroxyethyl hexahydrotriazine content and phosphoric acid-ethanol solution concentration. The polyurethane film PCL-PU2 prepared in Example 2, which exhibited good overall thermal stability and tensile properties, was completely degraded in a 2 mol / L phosphoric acid-ethanol solution at room temperature in just 2.2 hours.

[0089] The above-described embodiments are some preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any modifications, equivalent changes, alterations and simplifications made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a polycaprolactone-based functional polyurethane material, characterized in that, Includes the following steps: (1) Under a nitrogen atmosphere, isosorbide and hydroxyl-terminated polycaprolactone polyol were added to the reaction vessel and stirred and mixed evenly in the molten state. Then, diisocyanate monomer dissolved in an organic solvent was added to prepolymerize and obtain -NCO-terminated polyurethane prepolymer. (2) Continue to add hydroxyethyl hexahydrotriazine to the polymerization system in step (1), stir the reaction continuously, then pour the reaction solution into a polytetrafluoroethylene mold to level it, put it in a vacuum oven to evaporate the solvent and cure it completely to obtain a polyurethane film; In step (1), the molar ratio of isosorbide to hydroxyl-terminated polycaprolactone polyol is 4:2, 3:2, 2:2 or 1:2; In step (1), the stirring temperature is 60℃ and the time is 40 min; the diisocyanate monomer is added and reacted for 9-12 h at a reaction temperature of 120℃. The diisocyanate mentioned in step (1) includes one or more of hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and isoflurone diisocyanate; In step (2), the reaction is continuously stirred for 30 minutes and the reaction temperature is 60℃. The molar ratio of isosorbide to hydroxyethyl hexahydrotriazine is 3:1, 2:2 or 1:3; In step (2), the product is placed in a vacuum oven for drying for 20 hours at a temperature of 80°C.

2. The method for preparing a polycaprolactone-based functional polyurethane material as described in claim 1, characterized in that, The organic solvent mentioned in step (1) includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

3. A polycaprolactone-based functional polyurethane material prepared according to the method of claim 1 or 2.

4. An application of the polycaprolactone-based functional polyurethane material according to claim 3, characterized in that, It is applied to matrix materials for medical materials and flexible sensors.

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