Hydrophilic, bactericidal and antifouling mixed charge zwitterionic polyurethane coating as well as preparation method and application of hydrophilic, bactericidal and antifouling mixed charge zwitterionic polyurethane coating

Abstract

The invention discloses a hydrophilic, bactericidal and antifouling mixed charge zwitterionic polyurethane coating as well as a preparation method and application of the hydrophilic, bactericidal and antifouling mixed charge zwitterionic polyurethane coating. Multi-ion characteristics and intelligent response are realized, unique zwitterionic or mixed ionic polyurethane is created by simultaneously introducing positive ions (quaternary ammonium salt) and negative ions (carboxylate), and the material has pH responsiveness, electrostatic self-assembly capability, excellent protein adsorption resistance and biocompatibility, and can be used for preparing a composite material for preparing the composite material. The potential in the fields of intelligent coatings, drug controlled release and biomedical materials is huge.

Description

Technical Field

[0001] This invention relates to the field of membrane separation materials technology, and in particular to a hydrophilic, bactericidal, and antifouling mixed-charge zwitterionic polyurethane coating, its preparation method, and its application. Background Technology

[0002] Polyurethane materials are widely used in film coatings, paints, adhesives, and biomedical materials due to their excellent mechanical properties, wear resistance, and designability. However, traditional polyurethane materials have significant shortcomings in meeting the growing demand for high-end and functional materials, especially in areas such as long-lasting antibacterial properties, environmental friendliness, and multifunctional integration, where they face serious challenges.

[0003] Currently, the mainstream methods for imparting antibacterial properties to polyurethane are mostly physical blending of antibacterial agents (such as silver nanoparticles and quaternary ammonium salt small molecules) or surface coating modification. These methods have inherent drawbacks: physical blending easily leads to the migration and precipitation of antibacterial agents, resulting in a short antibacterial lifespan and potential biotoxicity or environmental pollution due to release; surface coatings are prone to wear and peeling, and their function is not durable. Therefore, developing a technology that chemically bonds long-lasting antibacterial groups to the polyurethane backbone is key to fundamentally solving the above problems.

[0004] Currently, single-function materials are insufficient to meet the demands of complex applications. For example, polyurethane materials combining long-lasting antibacterial properties and environmental friendliness (waterborne properties) are highly valuable, but their preparation faces technical challenges. Introducing hydrophilic groups (such as carboxyl groups) to achieve waterborne dispersion often interferes with the process of introducing antibacterial groups (such as quaternary ammonium salts). Quaternary ammonium salt cations and carboxylate anions are prone to flocculation or gelation due to electrostatic interactions during polymerization, leading to polymerization failure and product heterogeneity. How to integrate anionic and cationic functional groups into the same polymer chain in an orderly and controllable manner without phase separation or reaction interruption is a core scientific problem that needs to be solved in the preparation of high-performance, multifunctional polyurethanes.

[0005] Precise control of the purification and polymerization process of functional monomers is a prerequisite for obtaining materials with the desired structure. For example, the purity of dihydroxy quaternary ammonium salt (DQAS) monomers used for chain extension directly affects the performance and reproducibility of the final polymer. However, quaternary ammonium salts are highly polar and difficult to purify. Meanwhile, in the stepwise polymerization of polyurethanes, the molar ratio of functional groups, the reaction sequence, and the temperature directly affect the molecular weight, chain structure, and terminal groups. Without a complete process capable of precisely controlling the entire process from functional monomer synthesis and purification to multi-step sequential chain extension, it is difficult to achieve customizable material properties.

[0006] There is an urgent need in the current technological field for an innovative material design and synthesis strategy to solve the problem of the persistence and stable fixation of antibacterial groups in polyurethane, and how to overcome process limitations to integrate multiple (especially oppositely charged) functional groups on the same polymer chain, and establish a precise, reliable and repeatable synthesis and purification process. Summary of the Invention

[0007] The present invention aims to at least partially solve one of the technical problems in the related art.

[0008] Therefore, embodiments of the present invention propose a hydrophilic, bactericidal, and antifouling mixed-charge zwitterionic polyurethane coating, its preparation method, and its application.

[0009] In a first aspect, the present invention proposes a method for preparing a hydrophilic, bactericidal, and antifouling mixed-charge zwitterionic polyurethane coating, comprising the following steps: 1) Synthesis of cationic dihydroxy quaternary ammonium salt; (2) Dry polycaprolactone diol, isophorone diisocyanate, catalyst and solvent are added sequentially to the reactor and stirred in a dry inert gas atmosphere to obtain a prepolymer with isocyanate group end capping. (3) The cationic dihydroxy quaternary ammonium salt is added to the prepolymer, and the mixture is heated and stirred in a dry inert gas atmosphere. (4) Add dimethylolpropionic acid solution dropwise to the quaternary ammonium salt prepolymer obtained in step (3), stir the reaction in a dry inert gas atmosphere, add deionized water after the reaction is completed to form a pre-dispersion, remove the organic solvent to obtain a stable waterborne polyurethane dispersion.

[0010] Further, the synthesis of the cationic dihydroxy quaternary ammonium salt in step (1) includes: (a) Add N-methyldiethanolamine to the reaction vessel, then add acetonitrile as solvent, stir until the solution is homogeneous and transparent, and then cool the reaction vessel; (b) Under stirring and cooling conditions, ethyl 4-bromobutyrate was added dropwise to an acetonitrile solution of N-methyldiethanolamine; (c) After the reaction is complete, the acetonitrile is removed by vacuum distillation of the reaction solution under water bath conditions to obtain the crude product; (d) Dissolve the crude product completely in a warm solvent to form a clear solution; (e) The clarified solution is added dropwise to the precipitation solvent under stirring conditions to precipitate the cationic dihydroxy quaternary ammonium salt. After filtration, the precipitate is dried under vacuum to obtain the cationic dihydroxy quaternary ammonium salt.

[0011] Furthermore, the mass ratio of N-methyldiethanolamine to acetonitrile is 1:(3~4).

[0012] Furthermore, the molar ratio of ethyl 4-bromobutyrate to N-methyldiethanolamine is 1.05:1 to 1:1.

[0013] Furthermore, in step (a), the reaction vessel is cooled to 0~5°C.

[0014] Furthermore, the temperature of the water bath in step (c) is 40~50℃.

[0015] Furthermore, the temperature of the warm dissolving solvent in step (d) is 40~50°C.

[0016] Furthermore, in step (e), the vacuum drying is performed at 40~60°C for 12~24 hours.

[0017] Furthermore, the dissolving solvent includes at least one of ethanol, methanol, isopropanol, and acetonitrile.

[0018] Furthermore, the precipitation solvent includes at least one of ethyl acetate, diethyl ether, acetone, methyl tert-butyl ether (MTBE), and n-hexane.

[0019] Furthermore, the volume of the precipitating solvent is 5 to 10 times the volume of the dissolving solvent.

[0020] Furthermore, in step (2), the molar ratio of the isocyanate group provided by isophorone diisocyanate to the hydroxyl group provided by polycaprolactone diol is 2:1 to 5:1.

[0021] Furthermore, in step (2), the stirring reaction in a dry inert gas atmosphere is carried out at 70~80°C in a dry nitrogen atmosphere for 2~3 hours.

[0022] Furthermore, in step (3), after heating, the reaction is continued to be stirred in a dry inert gas atmosphere by raising the reaction temperature to 83~88℃ and continuing to stir the reaction under nitrogen protection for 2~3 hours.

[0023] Further, in step (3), the molar ratio of the hydroxyl group provided by the dihydroxy quaternary ammonium salt to the hydroxyl group provided by the polycaprolactone diol is 1:1 to 3:1.

[0024] Furthermore, in step (4), the molar ratio of the carboxylate anion provided by dimethylolpropionic acid to the quaternary ammonium salt cation is 1.1:1 to 1:1.1.

[0025] Furthermore, in step (4), the stirring reaction in a dry inert gas atmosphere is carried out at 80°C for 2-3 hours under a dry nitrogen atmosphere.

[0026] Secondly, the present invention provides a hydrophilic, bactericidal, and antifouling mixed-charge zwitterionic polyurethane coating prepared by the method described in the first aspect above.

[0027] Thirdly, the present invention proposes the application of the hydrophilic bactericidal and antifouling mixed-charge zwitterionic polyurethane coating prepared by the method proposed in the first aspect above, or the hydrophilic bactericidal and antifouling mixed-charge zwitterionic polyurethane coating proposed in the second aspect above, in the fields of smart coatings, drug controlled release, and biomedical materials.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention introduces long-lasting antibacterial properties in situ by directly embedding quaternary ammonium salt cations (DQAS) into the polyurethane backbone through chemical bonding, creating a non-leaching, long-lasting, and stable antibacterial surface. Compared with physical blending or surface coating, this method avoids the migration and failure of antibacterial agents, resulting in higher safety and a longer lifespan.

[0029] This invention achieves multiple ionic properties and "intelligent" response by simultaneously introducing cations (quaternary ammonium salts) and anions (carboxylates) to create a unique zwitterionic or mixed ionic polyurethane. This material can possess pH responsiveness, electrostatic self-assembly capability, excellent resistance to protein adsorption, and biocompatibility, and has great potential in the fields of smart coatings, drug controlled release, and biomedical materials.

[0030] This invention, from monomer synthesis to polymerization and chain extension, is based on chemometric control and reaction process monitoring (TLC, NCO value) throughout the entire process, ensuring that the molecular structure of each synthesized product is consistent and the performance is stable. Attached Figure Description

[0031] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart illustrating the preparation method of the hydrophilic, antibacterial, and antifouling mixed-charge zwitterionic polyurethane coating of the present invention. Figure 2 The 1H NMR spectrum of the cationic dihydroxy quaternary ammonium salt prepared in Example 1; Figure 3 Optical images of Escherichia coli and Staphylococcus aureus colonies on the coating surface during antibacterial performance testing of three polyurethane dispersions, M1, M2, and M2. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] The following description, in conjunction with the accompanying drawings, describes the hydrophilic, bactericidal, and antifouling mixed-charge zwitterionic polyurethane coating proposed in this invention, its preparation method, and its application.

[0034] like Figure 1 As shown, the preparation method of the hydrophilic, antibacterial, and antifouling mixed-charge zwitterionic polyurethane coating of the present invention includes the following steps: (1) Synthesis of cationic dihydroxy quaternary ammonium salt; (2) Dry polycaprolactone diol, isophorone diisocyanate, catalyst and solvent are added sequentially to the reactor and stirred in a dry inert gas atmosphere to obtain a prepolymer with isocyanate group end capping. (3) The cationic dihydroxy quaternary ammonium salt is added to the prepolymer, and the mixture is heated and stirred in a dry inert gas atmosphere. (4) Add dimethylolpropionic acid solution dropwise to the quaternary ammonium salt prepolymer obtained in step (3), stir the reaction in a dry inert gas atmosphere, add deionized water after the reaction is completed to form a pre-dispersion, remove the organic solvent to obtain a stable waterborne polyurethane dispersion.

[0035] Step (1) is the synthesis process of the cationic dihydroxy quaternary ammonium salt, which includes the following steps: (a) Add N-methyldiethanolamine to the reaction vessel, then add acetonitrile as solvent, stir until the solution is homogeneous and transparent, and then cool the reaction vessel; (b) Under stirring and cooling conditions, ethyl 4-bromobutyrate was added dropwise to an acetonitrile solution of N-methyldiethanolamine; (c) After the reaction is complete, the acetonitrile is removed by vacuum distillation of the reaction solution under water bath conditions to obtain the crude product; (d) Dissolve the crude product completely in a warm solvent to form a clear solution; (e) The clarified solution is added dropwise to the precipitation solvent under stirring conditions to precipitate the cationic dihydroxy quaternary ammonium salt. After filtration, the precipitate is dried under vacuum to obtain the cationic dihydroxy quaternary ammonium salt.

[0036] In step (a), acetonitrile is used as a solvent to dissolve N-methyldiethanolamine. The acetonitrile solution of N-methyldiethanolamine is stirred until the solution is homogeneous and transparent, and then the reaction vessel is cooled to 0~5℃.

[0037] In some embodiments, the mass ratio of N-methyldiethanolamine to acetonitrile is 1:(3~4). It is understood that the mass ratio of N-methyldiethanolamine to acetonitrile can be 1:3, 1:3.5, 1:4, or any value within a range of two such values.

[0038] In step (b), under appropriate cooling conditions, ethyl 4-bromobutyrate is slowly and dropwise added to an acetonitrile solution of N-methyldiethanolamine while stirring. During the reaction, thin-layer chromatography (TLC) monitoring shows no spots at the same Rf value positions as the ethyl 4-bromobutyrate standard, indicating complete reaction. The molar ratio of ethyl 4-bromobutyrate to N-methyldiethanolamine is 1.05:1 to 1:1.

[0039] After the reaction in step (c) is complete, the acetonitrile is removed by vacuum distillation of the reaction solution under water bath conditions of 40~50℃ to obtain the crude product.

[0040] In step (d), the crude product is completely dissolved in a warm solvent at 40-50°C to form a clear solution.

[0041] In step (e), the clarified solution is slowly and dropwise added to the precipitation solvent under stirring conditions. Immediately, a white or off-white solid cationic dihydroxy quaternary ammonium salt precipitates out. The precipitated solid is filtered and dried in a vacuum drying oven at 40-60°C for 12-24 hours to obtain the cationic dihydroxy quaternary ammonium salt. The volume of the precipitation solvent is 5-10 times that of the dissolving solvent, thereby enabling the cationic dihydroxy quaternary ammonium salt to precipitate quickly and completely.

[0042] The dissolving solvent includes at least one of ethanol, methanol, isopropanol, and acetonitrile, and the precipitation solvent includes at least one of ethyl acetate, diethyl ether, acetone, methyl tert-butyl ether (MTBE), and n-hexane.

[0043] Step (2) is the synthesis process of the prepolymer. Dry polycaprolactone diol, isophorone diisocyanate, catalyst and solvent are added sequentially to the reactor. The mixture is stirred and reacted at 70~80℃ in a dry nitrogen atmosphere for 2~3 hours to obtain a prepolymer with isocyanate groups at the end. The molar ratio of isocyanate groups provided by isophorone diisocyanate to hydroxyl groups provided by polycaprolactone diol is 2:1~5:1 to ensure that the ends of the prepolymer chains are capped with isocyanate groups.

[0044] Step (3) involves chain extension using a cationic dihydroxy quaternary ammonium salt. After the prepolymer is synthesized, the cationic dihydroxy quaternary ammonium salt is added to the prepolymer, and the reaction temperature is raised to 83-88°C. The reaction is continued under nitrogen protection with stirring for 2-3 hours. During this period, an appropriate amount of anhydrous N,N-dimethylformamide can be added according to the viscosity to maintain good stirring. The molar ratio of the hydroxyl groups provided by the dihydroxy quaternary ammonium salt to the hydroxyl groups provided by the polycaprolactone diol is 1:1 to 3:1, which gives the polyurethane strong antibacterial properties.

[0045] This invention introduces long-lasting antibacterial properties in situ by directly embedding quaternary ammonium salt cations (DQAS) into the polyurethane backbone through chemical bonding, creating a non-leaching, long-lasting, and stable antibacterial surface. Compared with physical blending or surface coating, this method avoids the migration and failure of antibacterial agents, resulting in higher safety and a longer lifespan.

[0046] Step (4) is the chain extension process using dimethylolpropionic acid solution. Specifically, dimethylolpropionic acid is placed in a reaction vessel, anhydrous N,N-dimethylformamide is added, and the mixture is heated (<60℃) and stirred or sonicated to completely dissolve it to obtain a dimethylolpropionic acid solution. The dimethylolpropionic acid solution is slowly added dropwise to the reaction flask containing the quaternary ammonium salt prepolymer obtained in step (3), and the reaction is carried out at 80℃ under a dry nitrogen atmosphere for 2-3 hours. After the reaction is completed, the polymer solution is slowly poured into deionized water under high-speed shear stirring, or deionized water is added to the polymer solution in the reverse direction to form a pre-dispersion. The organic solvent N,N-dimethylformamide in the system is completely removed by vacuum distillation or atmospheric distillation to obtain a stable waterborne polyurethane dispersion.

[0047] In some embodiments, the molar ratio of the carboxylate anion provided by dimethylolpropionic acid to the quaternary ammonium salt cation is 1.1:1 to 1:1.1.

[0048] This invention achieves multiple ionic properties and "intelligent" response by simultaneously introducing cations (quaternary ammonium salts) and anions (carboxylates) to create a unique zwitterionic or mixed ionic polyurethane. This material can possess pH responsiveness, electrostatic self-assembly capability, excellent resistance to protein adsorption, and biocompatibility, and has great potential in the fields of smart coatings, drug controlled release, and biomedical materials.

[0049] This invention, from monomer synthesis to polymerization and chain extension, is based on chemometric control and reaction process monitoring (TLC, NCO value) throughout the entire process, ensuring that the molecular structure of each synthesized product is consistent and the performance is stable.

[0050] The hydrophilic, antibacterial, and antifouling mixed-charge zwitterionic polyurethane coating of the present invention is prepared by the method of the present invention, and can be applied in the fields of smart coatings, drug controlled release, and biomedical materials.

[0051] The present invention will now be described in detail with reference to specific embodiments.

[0052] Example 1 (1) 11.9 g of N-methyldiethanolamine was added to the reaction vessel, and then 50 mL of acetonitrile was added as solvent. After stirring at room temperature until it became uniform and transparent, the reaction vessel was cooled to 5°C. Under stirring and appropriate cooling conditions, ethyl 4-bromobutyrate was slowly and dropwise added to the acetonitrile solution of N-methyldiethanolamine. During the process, thin-layer chromatography (TLC) was used to monitor the reaction. No spots were found at the same Rf value position as the ethyl 4-bromobutyrate standard, indicating that the reaction was complete. The amount of ethyl 4-bromobutyrate added was about 19.5 g. After the reaction, the solution was subjected to vacuum distillation at a water bath temperature of 40°C to remove most of the acetonitrile, and the crude product was obtained. The crude product was completely dissolved in warm ethanol at 40°C to form a clear solution. Under stirring, the hot solution was slowly and dropwise poured into a large amount of ethyl acetate, the volume of which was 10 times that of the ethanol. Immediately, a white or off-white solid precipitated out. The precipitated solid was filtered and dried in a vacuum drying oven at 50°C for 24 hours to obtain a high-purity cationic dihydroxy quaternary ammonium salt.

[0053] (2) Dissolve 5g of dried polycaprolactone diol, 2.775g of isophorone diisocyanate and 0.02g of dibutyltin dilaurate catalyst in 5mL of anhydrous N,N-dimethylformamide in a flask, and then stir the mixture for 2h under a dry nitrogen atmosphere at 80℃ to ensure that the ends of the prepolymer chain are capped by isocyanate groups to obtain the prepolymer. Then add 1.34g of cationic dihydroxy quaternary ammonium salt obtained in step (1) as a chain extender, and continue to stir the mixture at 85℃ under nitrogen protection for 2h. The viscosity of the polymer is adjusted by adding a certain amount of anhydrous N,N-dimethylformamide during the reaction to maintain good stirring.

[0054] (3) Place 0.74 g of dimethylolpropionic acid in a reaction vessel, add anhydrous N,N-dimethylformamide, heat at 50°C and stir to dissolve completely, slowly add to the reaction flask of step (2), maintain at 80°C, stir under dry nitrogen atmosphere for 2 hours, under high speed shear stirring, slowly pour the polymer solution into deionized water to form a pre-dispersion, and completely remove the organic solvent N,N-dimethylformamide in the system by vacuum distillation or atmospheric distillation to obtain a stable waterborne polyurethane dispersion M1.

[0055] Example 2 (1) 11.9 g of N-methyldiethanolamine was added to the reaction vessel, and then 50 mL of acetonitrile was added as solvent. After stirring at room temperature until it became uniform and transparent, the reaction vessel was cooled to 5°C. Under stirring and appropriate cooling conditions, ethyl 4-bromobutyrate was slowly and dropwise added to the acetonitrile solution of N-methyldiethanolamine. During the process, thin-layer chromatography (TLC) was used to monitor the reaction. No spots were found at the same Rf value position as the ethyl 4-bromobutyrate standard, indicating that the reaction was complete. The amount of ethyl 4-bromobutyrate added was about 19.5 g. After the reaction, the solution was subjected to vacuum distillation at a water bath temperature of 40°C to remove most of the acetonitrile, and the crude product was obtained. The crude product was completely dissolved in warm isopropanol at 40°C to form a clear solution. Under stirring, the hot solution was slowly and dropwise poured into a large amount of ethyl acetate, the volume of which was 10 times that of the isopropanol. Immediately, a white or off-white solid precipitated out. The precipitated solid was filtered and dried in a vacuum drying oven at 60°C for 12 hours to obtain a high-purity cationic dihydroxy quaternary ammonium salt.

[0056] (2) Dissolve 5g of dried polycaprolactone diol, 2.775g of isophorone diisocyanate and 0.02g of dibutyltin dilaurate catalyst in 5mL of anhydrous N,N-dimethylformamide in a flask, and then stir the mixture for 2h under a dry nitrogen atmosphere at 80℃ to ensure that the ends of the prepolymer chain are capped by isocyanate groups to obtain the prepolymer. Then add 1.34g of cationic dihydroxy quaternary ammonium salt obtained in step (1) as a chain extender, and continue to stir the mixture at 85℃ under nitrogen protection for 2h. The viscosity of the polymer is adjusted by adding a certain amount of anhydrous N,N-dimethylformamide during the reaction to maintain good stirring.

[0057] (3) Place 0.74 g of dimethylolpropionic acid in a reaction vessel, add anhydrous N,N-dimethylformamide, heat at 50°C and stir to dissolve completely, slowly add to the reaction flask of step (2), maintain at 80°C, stir under dry nitrogen atmosphere for 2 hours, under high speed shear stirring, slowly pour the polymer solution into deionized water to form a pre-dispersion, and completely remove the organic solvent N,N-dimethylformamide in the system by vacuum distillation or atmospheric distillation to obtain a stable waterborne polyurethane dispersion M1.

[0058] Example 3 (1) 11.9 g of N-methyldiethanolamine was added to the reaction vessel, and then 50 mL of acetonitrile was added as solvent. After stirring at room temperature until it became uniform and transparent, the reaction vessel was cooled to 5°C. Under stirring and appropriate cooling conditions, ethyl 4-bromobutyrate was slowly and dropwise added to the acetonitrile solution of N-methyldiethanolamine. During the process, thin-layer chromatography (TLC) was used to monitor the reaction. No spots were found at the same Rf value position as the ethyl 4-bromobutyrate standard, indicating that the reaction was complete. The amount of ethyl 4-bromobutyrate added was about 19.5 g. After the reaction, the solution was subjected to vacuum distillation at a water bath temperature of 40°C to remove most of the acetonitrile, and the crude product was obtained. The crude product was completely dissolved in warm ethanol at 40°C to form a clear solution. Under stirring, the hot solution was slowly and dropwise poured into a large amount of n-hexane, with the volume of n-hexane being 5 times the volume of ethanol. Immediately, a white or off-white solid precipitated out. The precipitated solid was filtered and dried in a vacuum drying oven at 50°C for 24 hours to obtain a high-purity cationic dihydroxy quaternary ammonium salt.

[0059] (2) Dissolve 5g of dried polycaprolactone diol, 2.775g of isophorone diisocyanate and 0.02g of dibutyltin dilaurate catalyst in 5mL of anhydrous N,N-dimethylformamide in a flask, and then stir the mixture for 2h under a dry nitrogen atmosphere at 80℃ to ensure that the ends of the prepolymer chain are capped by isocyanate groups to obtain the prepolymer. Then add 1.34g of cationic dihydroxy quaternary ammonium salt obtained in step (1) as a chain extender, and continue to stir the mixture at 85℃ under nitrogen protection for 2h. The viscosity of the polymer is adjusted by adding a certain amount of anhydrous N,N-dimethylformamide during the reaction to maintain good stirring.

[0060] (3) Place 0.74 g of dimethylolpropionic acid in a reaction vessel, add anhydrous N,N-dimethylformamide, heat at 50°C and stir to dissolve completely, slowly add to the reaction flask of step (2), maintain at 80°C, stir under dry nitrogen atmosphere for 2 hours, under high speed shear stirring, slowly pour the polymer solution into deionized water to form a pre-dispersion, and completely remove the organic solvent N,N-dimethylformamide in the system by vacuum distillation or atmospheric distillation to obtain a stable waterborne polyurethane dispersion M1.

[0061] Comparative Example 1 (1) Dissolve 5g of dry polycaprolactone diol, 2.775g of isophorone diisocyanate and 0.02g of dibutyltin dilaurate catalyst in 5mL of anhydrous N,N-dimethylformamide in a flask, and then stir the mixture for 2h under a dry nitrogen atmosphere at 80℃ to ensure that the ends of the prepolymer chain are capped by isocyanate groups to obtain the prepolymer.

[0062] (2) Place 0.74 g of dimethylolpropionic acid in a reaction vessel, add anhydrous N,N-dimethylformamide, heat at 50°C and stir to dissolve completely, slowly add to the reaction flask of step (1), maintain at 80°C, stir under dry nitrogen atmosphere for 2 hours, under high speed shear stirring, slowly pour the polymer solution into deionized water to form a pre-dispersion, and completely remove the organic solvent N,N-dimethylformamide in the system by vacuum distillation or atmospheric distillation to obtain a stable waterborne polyurethane dispersion M2.

[0063] Comparative Example 2 The difference from Example 1 is that dimethylolpropionic acid is not added in step (3) of Example 1, and the other processes are the same as in Example 1. The polyurethane dispersion prepared is denoted as M3.

[0064] Experimental Example 1 The product prepared in step (1) of Example 1 was subjected to 1H NMR spectroscopy, and the test results are as follows: Figure 2 As shown, from Figure 2 It can be seen that step (1) successfully synthesized the cationic dihydroxy quaternary ammonium salt.

[0065] Experimental Example 2 The three polyurethane dispersions obtained in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to Zeta and water contact angle tests. The test results are shown in Table 1 below.

[0066] Table 1:

[0067] Table 1 shows that the Zeta potentials of samples M1, M2, and M3 are approximately -8.54 mV, -30.6 mV, and 21.32 mV, respectively. Sample M1 has a Zeta potential close to 0 mV, indicating that it exhibits good resistance to non-specific protein adsorption and strong anti-adhesion capabilities. The water contact angles of samples M1, M2, and M3 are 22.43°, 54.21°, and 58.49°, respectively. Sample M1 has the smallest water contact angle, indicating that it has the best hydrophilicity. This also demonstrates that the Zeta potential and hydrophilicity of polyurethane can be adjusted by changing the ratio of cation / anion monomers.

[0068] Experimental Example 3 For antifouling performance testing, all samples were incubated at 37°C in the dark for 30 minutes with fluorescein isothiocyanate-bovine serum albumin (FITC-BSA) solution (0.1 mg / mL). The samples were then gently rinsed with phosphate-buffered saline to remove unadhered proteins. Adsorbed proteins on the samples were then observed using a confocal laser scanning microscope with the same imaging mode. To further elucidate the level of FITC-BSA adhesion, relative fluorescence intensity (RFI) was used for evaluation. The RFI of the original samples was set to 100%, and the RFI results were used to assess the adhesion level of FITC-BSA on the samples.

[0069] The three polyurethane dispersions obtained in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to RFI testing, and the test results are shown in Table 2 below.

[0070] Table 2:

[0071] Table 2 shows that M2 and M3 have high relative fluorescence intensity (RFI) values, indicating that a large amount of protein adheres to the surface of the coatings, resulting in poor anti-fouling performance. M1, on the other hand, has a very low relative fluorescence intensity (RFI) value, indicating that the coating effectively prevents protein contamination.

[0072] Test Example 4 For antimicrobial performance testing, all samples underwent a cleaning process prior to the antimicrobial assay, followed by sterilization under ultraviolet light for 30 minutes. Representative *Escherichia coli* and *Staphylococcus aureus* were selected to evaluate the antimicrobial activity of the samples. The bacterial suspension (100 μL, 6 × 10⁻⁶ μg / mL) was prepared according to a modified ISO 22196-2011 method. 5 CFU was dropped onto the sample surface, and then covered with a sterile polyethylene film (2×2cm). 2 The bacterial suspension was evenly distributed on the surface by covering the sample. After incubation at 37°C for 24 hours, all samples were washed with 5 mL of sterile PBS. Subsequently, the bacterial suspension was diluted 10-fold with sterile PBS. 20 μL of the diluted bacterial suspension was evenly distributed on agar plates for colony counting.

[0073] The antibacterial properties of the three polyurethane dispersions obtained in Example 1, Comparative Example 1, and Comparative Example 2 were tested, and the test results are shown in Table 3 below. Optical images of Escherichia coli and Staphylococcus aureus colonies on the coating surface are shown below. Figure 3 As shown.

[0074] Table 3:

[0075] According to Table 3 and Figure 3It is known that coatings M1 and M3 contain quaternary ammonium salt groups, and there are almost no bacteria on the surface of coatings M1 and M3, while coating M2 has a certain amount of viable bacteria. Quantitative results show that coatings M1 and M3 have a bactericidal rate of over 99% against E. coli and S. aureus, confirming that coatings M1 and M3 have excellent antibacterial effects.

[0076] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0077] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0078] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a hydrophilic, antibacterial, and antifouling mixed-charge zwitterionic polyurethane coating, characterized in that, Includes the following steps: (1) Synthesis of cationic dihydroxy quaternary ammonium salt; (2) Dry polycaprolactone diol, isophorone diisocyanate, catalyst and solvent are added sequentially to the reactor and stirred in a dry inert gas atmosphere to obtain a prepolymer with isocyanate group end capping. (3) The cationic dihydroxy quaternary ammonium salt is added to the prepolymer, and the mixture is heated and stirred in a dry inert gas atmosphere. (4) Add dimethylolpropionic acid solution dropwise to the quaternary ammonium salt prepolymer obtained in step (3), stir the reaction in a dry inert gas atmosphere, add deionized water after the reaction is completed to form a pre-dispersion, remove the organic solvent to obtain a stable waterborne polyurethane dispersion.

2. The method as described in claim 1, characterized in that, The synthesis of cationic dihydroxy quaternary ammonium salt in step (1) includes: (a) Add N-methyldiethanolamine to the reaction vessel, then add acetonitrile as solvent, stir until the solution is homogeneous and transparent, and then cool the reaction vessel; (b) Under stirring and cooling conditions, ethyl 4-bromobutyrate was added dropwise to an acetonitrile solution of N-methyldiethanolamine; (c) After the reaction is complete, the acetonitrile is removed by vacuum distillation of the reaction solution under water bath conditions to obtain the crude product; (d) Dissolve the crude product completely in a warm solvent to form a clear solution; (e) The clarified solution is added dropwise to the precipitation solvent under stirring conditions to precipitate the cationic dihydroxy quaternary ammonium salt. After filtration, the precipitate is dried under vacuum to obtain the cationic dihydroxy quaternary ammonium salt.

3. The method as described in claim 1, characterized in that, The mass ratio of N-methyldiethanolamine to acetonitrile is 1:(3~4). And / or, the molar ratio of ethyl 4-bromobutyrate to N-methyldiethanolamine is 1.05:1 to 1:

1.

4. The method as described in claim 1, characterized in that, In step (a), the reaction vessel is cooled to 0~5°C; And / or, the temperature of the water bath in step (c) is 40~50℃; And / or, the temperature of the warm dissolving solvent in step (d) is 40~50°C; And / or, in step (e), the vacuum drying is performed at 40~60°C for 12~24 hours; And / or, the dissolving solvent includes at least one of ethanol, methanol, isopropanol, and acetonitrile; And / or, the precipitation solvent includes at least one of ethyl acetate, diethyl ether, acetone, methyl tert-butyl ether (MTBE), and n-hexane; And / or, the volume of the precipitating solvent is 5 to 10 times the volume of the dissolving solvent.

5. The method as described in claim 1, characterized in that, In step (2), the molar ratio of the isocyanate group provided by isophorone diisocyanate to the hydroxyl group provided by polycaprolactone diol is 2:1 to 5:

1.

6. The method as described in claim 1, characterized in that, In step (2), the stirring reaction in a dry inert gas atmosphere is carried out at 70~80°C in a dry nitrogen atmosphere for 2~3 hours.

7. The method as described in claim 1, characterized in that, In step (3), after heating, the reaction is continued to be stirred in a dry inert gas atmosphere. The reaction temperature is raised to 83~88℃ and the reaction is continued to be stirred for 2~3 hours under nitrogen protection. And / or, in step (3), the molar ratio of the hydroxyl group provided by the dihydroxy quaternary ammonium salt to the hydroxyl group provided by the polycaprolactone diol is 1:1 to 3:

1.

8. The method as described in claim 1, characterized in that, In step (4), the molar ratio of the carboxylate anion provided by dimethylolpropionic acid to the quaternary ammonium salt cation is 1.1:1 to 1:1.

1. And / or, in step (4), the stirring reaction in a dry inert gas atmosphere is carried out at 80°C for 2-3 hours under a dry nitrogen atmosphere.

9. A hydrophilic, antibacterial, and antifouling mixed-charge zwitterionic polyurethane coating, characterized in that, Prepared by the method described in any one of claims 1 to 8.

10. The application of the hydrophilic bactericidal and antifouling mixed-charge zwitterionic polyurethane coating prepared by the method according to any one of claims 1 to 8, or the hydrophilic bactericidal and antifouling mixed-charge zwitterionic polyurethane coating according to claim 9, in the fields of smart coatings, drug controlled release, and biomedical materials.

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