Preparation method of polyimide / titanium dioxide composite hollow nanofiber aerogel

Abstract

The invention discloses a preparation method of polyimide / titanium dioxide composite hollow nanofiber aerogel, which comprises the following steps: by taking a polyamide acid solution as a shell layer spinning solution and a pore-foaming agent solution as a core layer spinning solution, preparing a polyamide acid composite nanofiber solution through a coaxial electrostatic spinning process; further drying to remove the solvent to obtain polyamide acid composite nanofibers; stirring and dispersing the polyamide acid composite nanofibers in a titanium compound aqueous solution to obtain a nano short fiber mixed dispersion liquid; the nano short fiber mixed dispersion liquid is hydrolyzed in deionized water, freeze drying and high-temperature treatment are carried out after hydrolysis, and the finished product is obtained.The specific surface area of the polyimide aerogel is increased through the pore-foaming agent, meanwhile, the density of the polyimide aerogel is reduced, the loading capacity of the titanium dioxide antibacterial agent is increased, and the better and longer antibacterial effect is achieved.

Description

Technical Field

[0001] The present invention relates to the field of polymer biomaterials, and in particular to a method for preparing a polyimide / titanium dioxide composite hollow nanofiber aerogel. Background Art

[0002] Skin, as the epidermal tissue of the human body, protects the body's internal environment and maintains its stability. The ultimate goal of treating skin injuries is to restore the skin's barrier function. Medical dressings are materials used to cover wounds, trauma, or surgical incisions, designed to protect the injured area, promote wound healing, and reduce the risk of infection. Currently, common medical dressings include various polymer films, hydrogels, sponges, and alginates. However, with society's increasing emphasis on health, higher requirements are being placed on the antimicrobial and comfort properties of medical dressings.

[0003] In the existing technology, common antimicrobial agents can be divided into natural, organic and inorganic systems. Natural antimicrobial agents are safe and environmentally friendly, but they have a short service life, poor heat resistance and a narrow range of applications. Organic antimicrobial agents have good bactericidal properties and efficiency, but they also have problems such as toxicity and easy decomposition at high temperatures. Therefore, people have gradually turned their research direction to inorganic antimicrobial agents. Some studies have loaded silver or zinc oxide on the surface of chitosan to improve the antimicrobial ability of dressings. However, silver is expensive and the biocompatibility of zinc oxide is not satisfactory. These are problems that urgently need to be solved in the dressing field. Overall, titanium dioxide is one of the most promising antimicrobial candidate materials and can be used to replace toxic organic and inorganic compound antimicrobial materials. It has excellent antimicrobial properties as well as non-toxicity, low cost, chemical stability at high temperatures and high photocatalytic performance.

[0004] Polyimide exhibits excellent solvent resistance, radiation resistance, dimensional stability, mechanical properties, and biocompatibility, demonstrating significant potential in biomedical applications. It is currently widely used clinically as a catheter for minimally invasive interventional therapy. Polyimide aerogel inherits these excellent properties of polyimide while also offering low density, high resilience, superhydrophobicity, flame retardancy, thermal insulation, and flexibility, making it an ideal substrate for medical dressings. However, polyimide itself lacks antibacterial properties, a crucial consideration in the medical field. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a polyimide / titanium dioxide composite hollow nanofiber aerogel.

[0006] The innovation of the present invention lies in that the specific surface area of the polyimide aerogel is increased by a porogen, the density of the polyimide aerogel is reduced, and the loading amount of the titanium dioxide antibacterial agent is increased to achieve a better and longer antibacterial effect.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0008] A method for preparing a polyimide / titanium dioxide composite hollow nanofiber aerogel comprises the following steps:

[0009] (1) using a polyamic acid solution as a shell spinning solution and a porogen solution as a core spinning solution, preparing a polyamic acid composite nanofiber solution by a coaxial electrospinning process, and further drying to remove the solvent to obtain polyamic acid composite nanofibers;

[0010] (2) stirring and dispersing the polyamic acid composite nanofibers in step (1) in an aqueous solution of a titanium compound to obtain a nanofiber mixed dispersion;

[0011] (3) The nanofiber mixed dispersion in step (2) is hydrolyzed in deionized water, and after hydrolysis, the mixture is freeze-dried and subjected to high-temperature treatment to obtain a finished product.

[0012] Furthermore, the solid content of the polyamic acid solution in step (1) is 1 to 40%; the solid content of the porogen solution is 1 to 50%.

[0013] Furthermore, the dianhydride monomer used in the synthesis of the polyamic acid solution is a mixture of any proportion of one or more of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 2,3',3,4'-biphenyl tetracarboxylic dianhydride, bisphenol A dianhydride, 4,4'-oxydiphthalic anhydride, hexafluoroisopropylene phthalic acid, diphenyl sulfide tetracarboxylic dianhydride and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride; The diamine monomer used in the synthesis of the amic acid solution is a mixture of one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole, 4,4'-diaminodiphenyl sulfone, and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl in any proportion; and the reaction solvent used in the synthesis of the polyamic acid solution is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-vinylpyrrolidone, and dimethyl sulfoxide.

[0014] Furthermore, the porogen in step (1) is a mixture of one or more of methyl methacrylate, cellulose acetate, polyethylene glycol, ammonium bicarbonate, and ammonium chloride in any proportion.

[0015] Furthermore, the drying treatment temperature in step (1) is 100-200° C., and the treatment time is 0.5-5 h.

[0016] Furthermore, the titanium compound in step (2) is a mixture of one or more of titanyl sulfate, titanium sulfate, titanium tetrachloride and titanium hydroxide in any proportion.

[0017] Furthermore, in step (2), the concentration of the titanium compound aqueous solution is 0.1 to 0.5 mol / L, and the stirring and dispersion time is 0.5 to 5 hours.

[0018] Furthermore, in step (3), the high temperature treatment temperature is 300-380° C., and the treatment time is 1-5 hours.

[0019] The beneficial effects of the present invention are:

[0020] 1. In the present invention, the specific surface area of the polyimide aerogel is increased by the porogen, the density of the polyimide aerogel is reduced, and the loading amount of the titanium dioxide antibacterial agent is increased, thereby achieving a better and longer antibacterial effect.

[0021] 2. The present invention uses a solution method to grow titanium dioxide directly on the surface of the nanofibers, eliminating the waste caused by the traditional method of directly adding titanium dioxide powder to the substrate. The titanium dioxide grown by the method of the present invention completely wraps around the substrate surface, forming a fully covered coaxial core-shell structure. Unlike the point-like active sites formed when adding powder, the titanium dioxide completely covers the substrate to form a surface, greatly increasing the number of active sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A photo of the preparation method of the polyimide / titanium dioxide composite hollow nanofiber aerogel prepared in Example 1 of the present invention

[0023] Figure 2 SEM image of the preparation method of polyimide / titanium dioxide composite hollow nanofiber aerogel prepared in Example 1 of the present invention

[0024] Figure 3 Water contact angle test of the preparation method of polyimide / titanium dioxide composite hollow nanofiber aerogel prepared in Example 1 of the present invention

[0025] Figure 4 The preparation method of the polyimide / titanium dioxide composite hollow nanofiber aerogel prepared in Example 1 of the present invention was subjected to 100 compression fatigue tests under 50% strain conditions. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings.

[0027] Example 1: A method for preparing a polyimide / titanium dioxide composite hollow nanofiber aerogel, comprising the following steps:

[0028] (1) Using polyamic acid solution as shell spinning solution and porogen solution as core spinning solution, a polyamic acid composite nanofiber solution was prepared by coaxial electrospinning process, the spinning voltage was 20 kV, the receiving distance was 20 cm, the shell propulsion speed was 0.9 mL / h, and the core propulsion speed was 0.3 mL / h; the solvent was further removed by drying treatment to obtain polyamic acid composite nanofibers, the drying treatment temperature was 100 ° C, and the treatment time was 0.5 h; the solid content of the polyamic acid solution was 1%; the solid content of the porogen solution was 1%, and the dianhydride monomer used in the synthesis of the polyamic acid solution was 3,3',4,4'-dibenzophenonetetracarboxylic dianhydride;

[0029] The diamine monomer used in the synthesis of the polyamic acid solution is p-phenylenediamine; the reaction solvent used in the synthesis of the polyamic acid solution is N,N-dimethylformamide; the porogen is methyl methacrylate;

[0030] (2) The polyamic acid composite nanofibers in step (1) are stirred and dispersed in a titanium compound aqueous solution to obtain a nanofiber mixed dispersion, wherein the titanium compound is titanyl sulfate, the concentration of the titanium compound aqueous solution is 0.1 mol / L, and the stirring and dispersion time is 0.5 h.

[0031] (3) The nanofiber mixed dispersion in step (2) is hydrolyzed in deionized water and ultrasonically cleaned three times for 5 minutes each time. Then, it is dispersed in a tert-butanol aqueous solution at a solid content of 1%. After hydrolysis, it is freeze-dried and subjected to high-temperature treatment to obtain a finished product. The high-temperature treatment temperature is gradually increased from 2°C / min to 300°C, and the treatment time is 1 hour.

[0032] Example 2: A method for preparing a polyimide / titanium dioxide composite hollow nanofiber aerogel, comprising the following steps:

[0033] (1) Using polyamic acid solution as shell spinning solution and porogen solution as core spinning solution, a polyamic acid composite nanofiber solution was prepared by coaxial electrospinning process, the spinning voltage was 20 kV, the receiving distance was 20 cm, the shell propulsion speed was 0.9 mL / h, and the core propulsion speed was 0.3 mL / h; the solvent was further removed by drying to obtain polyamic acid composite nanofibers, the drying temperature was 150 ° C, and the treatment time was 2 h; the solid content of the polyamic acid solution was 20%; the solid content of the porogen solution was 20%, the dianhydride monomer used in the synthesis of the polyamic acid solution was 3,3',4,4'-biphenyltetracarboxylic dianhydride; the diamine monomer used in the synthesis of the polyamic acid solution was m-phenylenediamine; the reaction solvent used in the synthesis of the polyamic acid solution was N,N-dimethylacetamide; the porogen was cellulose acetate;

[0034] (2) The polyamic acid composite nanofibers in step (1) are stirred and dispersed in a titanium compound aqueous solution to obtain a nanofiber mixed dispersion, wherein the titanium compound is titanium sulfate, the concentration of the titanium compound aqueous solution is 0.3 mol / L, and the stirring and dispersion time is 2 h.

[0035] (3) The nanofiber mixed dispersion in step (2) is hydrolyzed in deionized water, and after hydrolysis, the product is freeze-dried and subjected to high-temperature treatment at a temperature of 340° C.

[0036] The processing time is 3h.

[0037] Example 3: A method for preparing a polyimide / titanium dioxide composite hollow nanofiber aerogel, comprising the following steps:

[0038] (1) A polyamic acid solution is used as a shell spinning solution, a porogen solution is used as a core spinning solution, and a polyamic acid composite nanofiber solution is prepared by a coaxial electrospinning process. The polyamic acid composite nanofiber is further dried to remove the solvent. The drying temperature is 200°C and the treatment time is 5 hours. The solid content of the polyamic acid solution is 40%; the solid content of the porogen solution is 50%. The dianhydride monomer used in the synthesis of the polyamic acid solution is pyromellitic dianhydride; the diamine monomer used in the synthesis of the polyamic acid solution is 4,4'-diaminodiphenyl ether; and the reaction solvent is N-vinyl pyrrolidone.

[0039] (2) The polyamic acid composite nanofibers in step (1) are stirred and dispersed in a titanium compound aqueous solution to obtain a nanofiber mixed dispersion, wherein the titanium compound is titanium tetrachloride, the concentration of the titanium compound aqueous solution is 0.5 mol / L, and the stirring and dispersion time is 5 h.

[0040] (3) The nanofiber mixed dispersion in step (2) is hydrolyzed in deionized water, and after hydrolysis, the product is freeze-dried and subjected to high-temperature treatment at a temperature of 380° C. for 5 h.

[0041] Example 4: Referring to Example 1,

[0042] The dianhydride monomer used in the synthesis of the polyamic acid solution is a mixture of one or more of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, bisphenol A dianhydride, 4,4'-oxydiphthalic anhydride, hexafluoroisopropylenephthalic acid, diphenyl sulfide tetracarboxylic dianhydride and 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride in any proportion;

[0043] The diamine monomer used in the synthesis of the polyamic acid solution is a mixture of one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole, 4,4'-diaminodiphenyl sulfone, and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl in any proportion;

[0044] The reaction solvent used in the synthesis of the polyamic acid solution is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-vinyl pyrrolidone and dimethyl sulfoxide;

[0045] The porogen is a mixture of one or more of methyl methacrylate, cellulose acetate, polyethylene glycol, ammonium bicarbonate and ammonium chloride in any proportion.

[0046] Comparative Example 1: Referring to Example 1, no porogen solution was used.

[0047] Comparative Example 2: Referring to Example 1, step (2) was omitted.

[0048] Table 1 Comparison of the preparation methods and performance of polyimide / titanium dioxide composite hollow nanofiber aerogels prepared in the comparative example and the example

[0049]

[0050]

[0051] From the performance comparison of the embodiment and the comparative example in Table 1, it can be seen that the preparation method of the polyimide / titanium dioxide composite hollow nanofiber aerogel prepared by the method of the present invention has good bactericidal properties against Staphylococcus aureus and Escherichia coli, with an antibacterial rate of more than 98%. Compared with comparative example 1, the hollow nanofiber aerogel prepared in the embodiment has a lower density, indicating that it has better air permeability as a medical dressing and improves the comfort of use. Figure 2 Preparation method of polyimide / titanium dioxide composite hollow nanofiber aerogel SEM image shows that the nanofiber is a hollow structure and the titanium dioxide layer is evenly coated on the surface of the polyimide hollow nanofiber. Figure 3 The water contact angle test shows that the composite hollow nanofiber aerogel prepared by the present invention has super hydrophobicity, which effectively avoids secondary infection of wounds caused by pollutants such as sweat and water stains in daily life. Figure 4 Compression cycle fatigue testing demonstrated that the composite hollow nanofiber aerogel prepared by the present invention exhibited good flexibility and good adhesion between the titanium dioxide and polyimide substrates. This demonstrates that the polyimide / titanium dioxide composite hollow nanofiber aerogel prepared by the present invention exhibits promising application potential in the field of medical dressings.

[0052] The embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing a polyimide / titanium dioxide composite hollow nanofiber aerogel, characterized in that: The following steps are involved: (1) using a polyamic acid solution as a shell spinning solution and a porogen solution as a core spinning solution, preparing a polyamic acid composite nanofiber solution by a coaxial electrospinning process, and further drying to remove the solvent to obtain polyamic acid composite nanofibers; (2) stirring and dispersing the polyamic acid composite nanofibers in step (1) in an aqueous solution of a titanium compound to obtain a nanofiber mixed dispersion; (3) The nanofiber mixed dispersion in step (2) is hydrolyzed in deionized water, and after hydrolysis, freeze-dried and subjected to high-temperature treatment to obtain a finished product.

2. The method for preparing the polyimide / titanium dioxide composite hollow nanofiber aerogel according to claim 1, characterized in that: The solid content of the polyamic acid solution in step (1) is 1-40%; the solid content of the porogen solution is 1-50%.

3. The method for preparing the polyimide / titanium dioxide composite hollow nanofiber aerogel according to claim 1, characterized in that: The dianhydride monomer used in the synthesis of the polyamic acid solution is a mixture of one or more of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 2,3',3,4'-biphenyl tetracarboxylic dianhydride, bisphenol A dianhydride, 4,4'-oxydiphthalic anhydride, hexafluoroisopropylene phthalic acid, diphenyl sulfide tetracarboxylic dianhydride and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride in any proportion; the polyamide The diamine monomer used for the acid solution synthesis is a mixture of one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole, 4,4'-diaminodiphenyl sulfone, and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl in any proportion; and the reaction solvent used for the polyamic acid solution synthesis is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-vinylpyrrolidone, and dimethyl sulfoxide.

4. The method for preparing the polyimide / titanium dioxide composite hollow nanofiber aerogel according to claim 1, characterized in that: The porogen in step (1) is a mixture of one or more of methyl methacrylate, cellulose acetate, polyethylene glycol, ammonium bicarbonate, and ammonium chloride in any proportion.

5. The method for preparing the polyimide / titanium dioxide composite hollow nanofiber aerogel according to claim 1, characterized in that: The drying treatment temperature in step (1) is 100-200° C., and the treatment time is 0.5-5 h.

6. The method for preparing the polyimide / titanium dioxide composite hollow nanofiber aerogel according to claim 1, characterized in that: The titanium compound in step (2) is a mixture of one or more of titanyl sulfate, titanium sulfate, titanium tetrachloride and titanium hydroxide in any proportion.

7. The method for preparing the polyimide / titanium dioxide composite hollow nanofiber aerogel according to claim 1, characterized in that: In step (2), the concentration of the titanium compound aqueous solution is 0.1-0.5 mol / L, and the stirring and dispersion time is 0.5-5 h.

8. The method for preparing the polyimide / titanium dioxide composite hollow nanofiber aerogel according to claim 1, characterized in that: In step (3), the high temperature treatment temperature is 300-380° C., and the treatment time is 1-5 hours.

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