Membrane material containing porous polymeric nanofibers and method for making the same

Abstract

The application provides a porous polymer nanofiber-containing membrane material and a preparation method thereof. The method is based on mature melt phase separation scale nanofiber preparation, thermoplastic block copolymer is blended with CAB to form a thermodynamically incompatible system, and the thermoplastic block copolymer is subjected to phase separation self-assembly under the coupling of temperature, phase boundary, shear force and tensile force and the like in a melt spinning process, so that fiber formation is realized and the construction of the secondary physical structure of the nanofiber itself is realized. The polymer nanofiber is subjected to selective solvent induction and heat treatment to self-assemble the nanofiber, so that the nanofiber has a multi-level pore structure, and the nanofiber has an ultrahigh specific surface area and high porosity. Moreover, the components of the polymer used have various active functional groups, so that the porous polymer nanofiber-containing membrane material prepared is easy to be modified in various forms, and the application field of the nanofiber membrane is greatly expanded.

Description

Technical Field

[0001] This invention relates to the field of textile materials technology, and in particular to a membrane material containing porous polymer nanofibers and its preparation method. Background Technology

[0002] Nanofibers, due to their large aspect ratio, large specific surface area, and ease of membrane formation, are widely used in medicine, food, environment, energy, and other fields. Current membrane nanofibers have diameters reaching tens or even hundreds of nanometers; however, due to their simple fiber structure, their specific surface area still cannot meet the demands of high-efficiency, high-speed filtration, separation, and purification applications. Constructing hierarchical porous structures using polymer fibers has become a technological trend in the preparation of high specific surface area materials. Polymer fiber aggregates possess a unique fiber skeleton structure, high porosity, and ease of functionalization; moreover, the fiber preparation process is simple, functionalization and pore-forming processes are relatively independent, and the structure is highly controllable, making them a powerful tool for preparing porous polymer monolithic materials. Currently, methods such as pore-forming agent blending, block copolymer microphase separation pore formation, and blending of polymers with different conformations can prepare porous fibers with mesoporous structures in the bulk or on the surface, increasing the specific surface area to 500 m². 2 / g or higher. The pore structures in the above studies were all formed during the phase separation process of polymer or segment multiphase systems. Heat treatment or solvent treatment can reconstruct or remove the molecular chains after phase separation, creating cavities and thus forming pore structures. However, the shortcomings of the above studies are that the microscopic size of the polymer or segment blend phase is usually in the range of 10nm to 100nm, and the obtained pore sizes are mostly at the mesopore or macropore level, making it difficult to construct small pores. Furthermore, due to the flexibility of the polymer molecular chains themselves and the lack of inter-chain chemical interactions, the fiber channels remain unstable and will collapse under the influence of solvents or heat.

[0003] In contrast, there are numerous reports on techniques and methods for preparing porous flat sheet membrane materials using block copolymers. These methods primarily involve selectively swelling a pre-formed block copolymer film with a solvent to remove one component, thereby obtaining a porous structure. For example, patent CN156270A discloses a method for controlling the self-assembly morphology of block copolymer templates for nanofabrication. This method dissolves styrene block copolymers in xylene, casts them onto a substrate surface, allows them to evaporate naturally to form a film, and then adds organic solvent to obtain porous patterns on the scale of several hundred nanometers. Patent CN101361170A discloses a method for manufacturing nanoporous substrates. This method involves immersing an amphiphilic block copolymer coated on a substrate in an etching solvent to obtain a nanoporous substrate with a pore diameter of 3–40 nm and a pore spacing of less than 60 nm. Patent CN103374142A discloses a method for preparing porous membranes using (AB)n type block copolymers. This patent dissolves the (AB)n type block copolymer in DMF, toluene, isopropanol, or mixtures thereof, and coats and dries it at 110–150°C to obtain a nanoporous structure with a pore size of 35–40 nm. Patent CN104028123A discloses a method for preparing polymer nanofiber separation membranes. This patent forms a membrane by combining block polymers and additives or fillers in one or more selective methods, and then gels the membrane in a coagulation bath containing the block polymer to form a polymer nanofiber separation membrane with a porosity of 10–90% and a pore size of 10–90 nm. The membranes prepared by the above methods are planar porous membranes rather than nanofiber membranes. Their specific surface area and porosity are much smaller than conventional nanofiber membranes, making the pores easily clogged and resulting in poor antifouling performance. Furthermore, the final polymer has very few active functional groups, making further functionalization difficult.

[0004] In view of this, it is necessary to design a membrane material containing porous polymer nanofibers and its preparation method to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a membrane material containing porous polymer nanofibers and its preparation method. This method not only obtains nanofibers with fractal structures, further increasing the specific surface area of ​​the nanofibers themselves, but also overcomes the technical bottleneck of the prior art in simultaneously achieving the preparation of multi-level porous nanofibers and nanofiber membranes by the random stacking of nanofibers with fractal structures.

[0006] To achieve the above objectives, the present invention provides a method for preparing a membrane material containing porous polymer nanofibers, comprising the following steps:

[0007] S1. Two or more different monomers are subjected to block copolymerization to obtain thermoplastic block copolymers;

[0008] S2. After uniformly mixing the thermoplastic block copolymer with cellulose acetate butyrate, the mixture is melted, spun, and drawn to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber.

[0009] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is placed in acetone and refluxed to extract cellulose acetate butyrate, thereby obtaining thermoplastic block copolymer composite fiber; the thermoplastic block copolymer composite fiber is then dried to obtain polymer nanofibers.

[0010] S4. The polymer nanofibers are subjected to heat treatment under vacuum or inert gas to obtain heat-treated polymer nanofibers.

[0011] S5. The heat-treated polymer nanofibers are placed in a mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0012] S6. The pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent for swelling. After swelling, a catalyst is added to carry out a hypercrosslinking reaction, thereby obtaining porous polymer nanofibers with fractal structure.

[0013] S7. The porous polymer nanofibers with fractal structure are dispersed in solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on the surface of a substrate. After drying, the substrate is removed to obtain a membrane material containing porous polymer nanofibers.

[0014] Further, in step S1, the monomer includes one of ethylene glycol, monomethyl ether polyoxyethylene, hydroxylated polystyrene, glycidyl methacrylate, 2-vinylpyridine, 4-vinylpyridine, acrylamide, 4-aminostyrene, 4-hydroxystyrene, p-chloromethylstyrene, acrylic acid, N-isopropylacrylamide, and ethylene oxide.

[0015] Further, in step S2, the mass percentage of the thermoplastic block copolymer to the cellulose acetate butyrate is 5-50:50-95.

[0016] Furthermore, in step S3, the reflux temperature is 60℃~90℃, the reflux time is 24~72h, and the diameter of the obtained polymer nanofibers is 50~1000nm.

[0017] Furthermore, in step S4, the heat treatment is carried out at a temperature of 50–300°C for 1–24 hours, and the inert gas includes either nitrogen or argon.

[0018] Further, in step S5, the mixed solution A comprises a mixed solution consisting of a poor solvent I, a catalyst, and a crosslinking agent; the catalyst comprises one of ferric chloride and zinc chloride; the crosslinking agent comprises dimethoxymethane; and the poor solvent I comprises one or more of acetic acid and dimethyl sulfoxide.

[0019] Furthermore, the specific process of the pre-crosslinking treatment in step S5 is as follows:

[0020] The heat-treated polymer nanofibers are placed in a mixed solution A at 70–90°C for 1–80 min. Then, the heat-treated polymer nanofibers are dried at 10°C–110°C under normal pressure until the heat-treated polymer nanofibers maintain a constant weight, thus obtaining pre-crosslinked block copolymer nanofibers.

[0021] Further, in step S6, the good solvent II includes one or more of 1,2-dichloroethane, dichloromethane, and chloroform; the crosslinking agent includes dimethoxymethane; the catalyst includes one of ferric chloride and zinc chloride; the swelling temperature is 20-30°C, and the swelling time is 1-300 min.

[0022] Further, in step S7, the concentration of the porous polymer nanofibers with fractal structure dispersed in solvent III is 0.5–2.0 g / L; the coating basis weight is 0.5–100 g / m³. 2 Solvent III includes two or more of the following: water, tetrahydrofuran, ethanol, and acetone.

[0023] The present invention also provides a membrane material containing porous polymer nanofibers prepared by the preparation method described above, wherein the average diameter of the nanofibers in the membrane material containing porous polymer nanofibers is 50-1000 nm, the membrane material containing porous polymer nanofibers has a hierarchical pore structure, and the average diameter of the nanofibers in the membrane material containing porous polymer nanofibers is greater than the average pore size of the hierarchical pore structure.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention provides a method for preparing membrane materials containing porous polymer nanofibers. Based on mature melt phase separation technology for large-scale nanofiber preparation, a thermoplastic block copolymer is blended with cellulose acetate butyrate (CAB) to form a thermodynamically incompatible system. During melt spinning, the thermoplastic block copolymer undergoes phase separation and self-assembly under the coupled effects of multiple fields such as temperature, phase boundary, shear force, and tensile force. This achieves the construction of the secondary physical structure of the nanofibers themselves while forming fibers, providing a rapid and efficient preparation route for nanofiber membranes with hierarchical structures. Furthermore, porous polymer nanofibers with hierarchical fractal structures are synthesized by selective solvent-induced heat treatment of polymer nanofibers for self-assembly. These nanofibers can also be dispersed in a specific solvent to achieve batch film formation, overcoming the technical bottleneck of existing methods that struggle to simultaneously achieve the preparation of nanofibers with hierarchical pore structures and nanofiber membranes.

[0026] 2. The membrane material containing porous polymer nanofibers provided by the present invention has a fractal structure, and the fractal nanofibers eventually form a multi-level pore structure of nanofibers through random stacking. Compared with conventional nanofiber membranes, it has a higher specific surface area and a multi-scale pore structure.

[0027] 3. This invention provides a membrane material containing porous polymer nanofibers. The polymer components used contain multiple active functional groups, making the final porous polymer nanofiber membrane material easy to undergo various forms of functionalization modification, greatly expanding the application fields of nanofiber membranes. Therefore, it shows significant application potential in media filtration and purification, affinity separation and purification, membrane catalysis, bioelectronic sensing, biomedicine and medical fields.

[0028] 4. The membrane material containing porous polymer nanofibers provided by the present invention relies on the independence of the film formation technology, so that the nanofiber membrane has the characteristic of controllable three-dimensional structure. Attached Figure Description

[0029] Figure 1 (a) is a planar view of the porous polymer nanofibers with a core-skin structure and a fractal structure in Example 5; (b) is a cross-sectional view.

[0030] Figure 2 Electron micrographs of nanofiber membranes made from polystyrene, butadiene, and polystyrene through spinning: (a) is a planar view; (b) is a cross-sectional view.

[0031] Figure 3 This is a schematic diagram of the morphology of a nanofiber membrane obtained by spinning polystyrene-butadiene-polystyrene after hypercrosslinking. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0034] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0035] A method for preparing a membrane material containing porous polymer nanofibers includes the following steps:

[0036] S1. A block copolymerization reaction is carried out between two or more different monomers to obtain a thermoplastic block copolymer; at least one of the selected monomers has a homopolymer that can be swollen or dissolved by an organic or inorganic solvent, and the homopolymer of the monomers cannot be swollen or dissolved by a single solvent at the same time; in addition, at least one monomer has one or more active functional groups of hydroxyl, amino, carboxyl or amide groups after the block copolymerization reaction.

[0037] S2. After uniformly mixing the thermoplastic block copolymer with cellulose acetate butyrate (CAB), the mixture is melted, spun, and drawn using a twin-screw melt spinning machine to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber; the processing temperature of the twin-screw melt spinning machine is 100-300℃;

[0038] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 24-72 hours to extract cellulose acetate butyrate, thus obtaining thermoplastic block copolymer composite fiber; then the thermoplastic block copolymer composite fiber is dried at room temperature to obtain polymer nanofibers with a diameter of 50-1000 nm.

[0039] Reflux temperature is 60℃~90℃;

[0040] S4. The polymer nanofibers are subjected to heat treatment under vacuum or inert gas to obtain heat-treated polymer nanofibers.

[0041] In step S4, the heat treatment is carried out at a temperature of 50 to 300°C for 1 to 24 hours, and the inert gas includes one of nitrogen and argon.

[0042] S5. The heat-treated polymer nanofibers are placed in a mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0043] The mixed solution A comprises a mixed solution consisting of a poor solvent I, a catalyst, and a crosslinking agent; the catalyst comprises one of ferric chloride and zinc chloride; the crosslinking agent comprises dimethoxymethane; and the poor solvent I comprises one or more of acetic acid and dimethyl sulfoxide.

[0044] S6. At 20-30°C, the pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 1-300 min. After swelling, a catalyst is added and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with fractal structure.

[0045] The undesirable solvent II comprises a solution of one or more mixtures of 1,2-dichloroethane, dichloromethane, and chloroform; the crosslinking agent comprises dimethoxymethane; and the catalyst comprises one of ferric chloride and zinc chloride.

[0046] S7. The porous polymer nanofibers with fractal structure are dispersed in solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on the surface of a nonwoven fabric substrate and dried at room temperature to obtain a composite membrane containing porous polymer nanofibers. The nonwoven fabric substrate is then removed to obtain a membrane material containing porous polymer nanofibers.

[0047] The porous polymer nanofibers with fractal structures are dispersed in solvent III at a concentration of 0.5–2.0 g / L; the coating weight is 0.5–100 g / m³. 2 Solvent III includes two or more of the following: water, tetrahydrofuran, ethanol, and acetone.

[0048] This setup, based on mature melt phase separation technology for large-scale nanofiber fabrication, involves blending thermoplastic block copolymers with cellulose acetate butyrate (CAB) to form a thermodynamically incompatible system. During melt spinning, the thermoplastic block copolymers undergo phase separation and self-assembly under the coupled effects of multiple fields, including temperature, phase boundaries, shear force, and tensile force, thus simultaneously constructing the secondary physical structure of the nanofibers. Furthermore, porous polymer nanofibers with hierarchical fractal structures are synthesized through selective solvent-induced heat treatment of polymer nanofibers. These nanofibers can also be dispersed in specific solvents to achieve batch film formation.

[0049] Specifically, in some embodiments of the present invention, in step S1, the monomer includes one of ethylene glycol, monomethyl ether polyoxyethylene, hydroxylated polystyrene, glycidyl methacrylate, 2-vinylpyridine, 4-vinylpyridine, acrylamide, 4-aminostyrene, 4-hydroxystyrene, p-chloromethylstyrene, acrylic acid, N-isopropylacrylamide, and ethylene oxide.

[0050] Preferably, the thermoplastic block copolymers include: hydroxylated polystyrene-polyethylene glycol block copolymer PS(OH)-b-PEG-b-PS(OH) (the monomer composition includes hydroxylated styrene and ethylene glycol; wherein the ethylene glycol has an active hydroxyl group, and the alcoholic or phenolic hydroxyl groups on the hydroxylated styrene segments are grafted onto polyamines in the aqueous phase under the action of glutaraldehyde), and hydroxylated polystyrene-polyoxyethylene block copolymer (PS(OH)-b-PEO) (the monomer composition includes styrene and ethylene oxide; wherein the ethylene oxide has a highly active epoxy functional group, which has... (Strong electrophilic and nucleophilic properties), hydroxylated polystyrene-polymethyl methacrylate block copolymer (PS(OH)-b-PMMA) (involving monomers including hydroxylated styrene and methyl methacrylate; where methyl methacrylate has an active carboxyl group), hydroxylated polystyrene-polyethyl methacrylate block copolymer (PS(OH)-b-PEMA) (involving monomers including hydroxylated styrene and ethyl methacrylate; where ethyl methacrylate has an active carboxyl group), polystyrene-butadiene-polystyrene (SBS) (involving monomers including styrene and butadiene; where butadiene has two highly reactive double bonds), hydrogenated polystyrene-butadiene-polystyrene (Styrene EthyleneButylene) Styrene (SEBS) (the monomers involved include hydrogenated styrene and butadiene; where butadiene has two highly reactive double bonds), poly(4-aminostyrene-b-polyglycidyl methacrylate) (PAS-b-PGMA) (the monomers involved include 4-aminostyrene and glycidyl methacrylate; where 4-aminostyrene has an active amino group and glycidyl methacrylate has an active carboxyl group), poly(p-chloromethylstyrene-b-polyglycidyl methacrylate-b-poly2-vinylpyridine) (PCMS-b-PGMA-b-P2VP) (the monomers involved include p-chloromethylstyrene, glycidyl methacrylate, and...) 2-Vinylpyridine; wherein glycidyl methacrylate has an active carboxyl group), poly(4-hydroxystyrene-b-poly(glycidyl methacrylate-b-poly(4-aminostyrene)) (the monomer composition involves 4-hydroxystyrene, glycidyl methacrylate and 4-aminostyrene; wherein 4-hydroxystyrene has an active hydroxyl group, glycidyl methacrylate has an active carboxyl group and 4-aminostyrene has an active amino group), poly(4-hydroxystyrene-b-poly(N-isopropylacrylamide)) (the monomer composition involves 4-hydroxystyrene and N-isopropylacrylamide);Among them, 4-hydroxystyrene has an active hydroxyl group, and N-isopropylacrylamide has an active amide group; poly(p-chloromethylstyrene)-b-polyglycidyl methacrylate-b-poly2-vinylpyridine (PCMS-b-PGMA-b-P2VP) (the monomer composition involves p-chloromethylstyrene, glycidyl methacrylate, and 2-vinylpyridine; wherein glycidyl methacrylate has an active carboxyl group).

[0051] With this setup, the polymer components have a variety of active functional groups, which makes the final porous polymer nanofiber membrane material easy to undergo various forms of functionalization modification, greatly expanding the application fields of nanofiber membranes.

[0052] Specifically, in some embodiments of the present invention, the mass percentage of the thermoplastic block copolymer to the cellulose acetate butyrate in step S2 is 5-50:50-95.

[0053] Specifically, in some embodiments of the present invention, the pre-crosslinking treatment in step S5 is carried out as follows: the heat-treated polymer nanofibers are placed in a mixed solution A at 70-90°C and reacted for 1-80 minutes; then the heat-treated polymer nanofibers are dried at 10-110°C under normal pressure and volatilized until the heat-treated polymer nanofibers maintain a constant weight, thereby obtaining pre-crosslinked block copolymer nanofibers.

[0054] With this setup, porous polymer nanofibers with multi-level channel fractal structures are synthesized by selectively solvent-induced heat treatment of polymer nanofiber self-assembly.

[0055] The present invention also provides a membrane material containing porous polymer nanofibers prepared by the aforementioned preparation method; the average diameter of the nanofibers in the membrane material containing porous polymer nanofibers is 50-1000 nm, and the membrane material containing porous polymer nanofibers has a hierarchical pore structure (the hierarchical pore structure is composed of macropores, mesopores, and micropores formed by fiber stacking during polymer self-crosslinking); the average diameter of the nanofibers in the membrane material containing porous polymer nanofibers is greater than the average pore diameter of the hierarchical pore structure or the average size of the protrusions generated during the fiber reaction.

[0056] This configuration allows for the preparation of membrane materials containing porous polymer nanofibers. Due to their fractal structure, and the fact that these fractal nanofibers form a hierarchical pore structure through random stacking, these membrane materials exhibit a higher specific surface area and a wider range of pore sizes compared to conventional nanofiber membranes. Furthermore, the polymer components contain various active functional groups, making the prepared porous polymer nanofiber membrane materials readily adaptable to different functionalization methods. This results in significant application potential in fields such as media filtration and purification, affinity separation and purification, membrane catalysis, bioelectronic sensing, biomedicine, and healthcare.

[0057] The following examples illustrate the membrane material containing porous polymer nanofibers and its preparation method provided by the present invention:

[0058] Example 1

[0059] This embodiment provides a method for preparing a membrane material containing porous polymer nanofibers, specifically including the following steps:

[0060] S1. Hydroxylated polystyrene and polyethylene glycol monomers are subjected to block copolymerization to obtain a thermoplastic block copolymer;

[0061] S2. Mix 1 kg of the thermoplastic block copolymer with 4 kg of cellulose acetate butyrate (CAB) evenly, and vacuum dry it at 70°C for 12 h in a vacuum drying oven. Then, melt, spin and draw it using a twin-screw melt spinning machine at 180°C to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber.

[0062] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 72 hours to extract cellulose acetate butyrate, thus obtaining thermoplastic block copolymer composite fiber; then the thermoplastic block copolymer composite fiber is dried at room temperature to obtain polymer nanofibers with an average diameter of 200 nm; wherein the reflux temperature is 60 °C.

[0063] S4. The polymer nanofibers are placed in a vacuum at 100°C for 8 hours to obtain heat-treated polymer nanofibers.

[0064] S5. Place 10g of the heat-treated polymer nanofibers in mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0065] The mixed solution A is a mixture of undesirable solvent I, catalyst, and crosslinking agent; the catalyst is ferric chloride; the crosslinking agent is dimethoxymethane; and the undesirable solvent I is acetic acid.

[0066] The specific process of pre-crosslinking treatment is as follows: at 80°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 60 min; then the heat-treated polymer nanofibers are dried at 60°C under normal pressure and volatilized until the heat-treated polymer nanofibers maintain a constant weight to obtain pre-crosslinked block copolymer nanofibers.

[0067] S6. At 25°C, the pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 300 min. After swelling, a catalyst is added and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with a fractal structure of funnel shape (wherein the pores are composed of macropores-mesopores-micropores).

[0068] The good solvent II is 1,2-dichloroethane; the crosslinking agent is dimethoxymethane; and the catalyst is ferric chloride.

[0069] S7. Under the action of high-speed shear force, 5g of the porous polymer nanofibers with fractal structure are dispersed in 500g of solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on a surface with an area of ​​2m². 2 Density is 60 g / m³ 2 A 10μm thick coating is applied to the surface of a PP (polypropylene) meltblown nonwoven fabric substrate and dried in a fume hood to obtain a composite membrane containing porous polymer nanofibers. The nonwoven fabric substrate is then removed to obtain a membrane material containing porous polymer nanofibers.

[0070] The porous polymer nanofibers with fractal structure are dispersed in solvent III at a concentration of 10 g / L; the coating weight is 10 g / m³. 2 Solvent III is a mixture of tetrahydrofuran and N,N-dimethylformamide in a mass ratio of 1:1.

[0071] Example 2

[0072] Example 2 provides a membrane material containing porous polymer nanofibers and its preparation method, which differs from Example 1 in that:

[0073] S1. Hydroxylated polystyrene and ethylene oxide monomers are subjected to block copolymerization to obtain a thermoplastic block copolymer;

[0074] S2. Mix 1.5 kg of thermoplastic block copolymer with 3.5 kg of cellulose acetate butyrate (CAB) evenly, and vacuum dry it at 70°C for 12 h in a vacuum drying oven. Then, melt, spin and draw it using a twin-screw melt spinning machine at 220°C to obtain polymer / cellulose acetate butyrate composite fiber.

[0075] S3. The polymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 72 hours to extract cellulose acetate butyrate and obtain polymer fiber; then the polymer fiber is dried at room temperature to obtain polymer nanofibers with an average diameter of 300 nm; wherein the reflux temperature is 70 °C.

[0076] S4. The polymer nanofibers are placed in a vacuum at 80°C for 8 hours to obtain heat-treated polymer nanofibers.

[0077] S5. Place 10g of the heat-treated polymer nanofibers in mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked polymer nanofibers;

[0078] The mixed solution A is a mixture of undesirable solvent I, catalyst, and crosslinking agent; the catalyst is ferric chloride; the crosslinking agent is dimethoxymethane; and the undesirable solvent I is dimethyl sulfoxide.

[0079] The specific process of the pre-crosslinking treatment in step S5 is as follows: at 80°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 70 min; then the heat-treated polymer nanofibers are dried at 60°C under normal pressure and volatilized until the heat-treated polymer nanofibers maintain a constant weight to obtain pre-crosslinked polymer nanofibers.

[0080] S6. At 25°C, the pre-crosslinked polymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 300 min. After swelling, a catalyst is added and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with a fractal structure in the shape of a trumpet (wherein the pores are composed of macropores-mesopores-micropores).

[0081] The good solvent II is 1,2-dichloroethane; the crosslinking agent is dimethoxymethane; and the catalyst is ferric chloride.

[0082] S7. Under the action of high-speed shear force, 5g of the porous polymer nanofibers with fractal structure are dispersed in 500g of solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on a surface with an area of ​​2m². 2 Density is 60 g / m³ 2 A 10μm thick PET (polyethylene terephthalate) meltblown nonwoven fabric substrate is coated on its surface and dried in a fume hood to obtain a composite membrane containing porous polymer nanofibers. The nonwoven fabric substrate is then removed to obtain a membrane material containing porous polymer nanofibers.

[0083] The porous polymer nanofibers with fractal structure are dispersed in solvent III at a concentration of 10 g / L; the coating weight is 8 g / m³.2 Solvent III is a mixture of tetrahydrofuran and N,N-dimethylformamide in a mass ratio of 2:3.

[0084] Example 3

[0085] Example 3 provides a membrane material containing porous polymer nanofibers and its preparation method, specifically including the following steps:

[0086] S1. Hydroxylated polystyrene and polymethyl methacrylate monomers are subjected to block copolymerization to obtain a thermoplastic block copolymer;

[0087] S2. Mix 1 kg of the thermoplastic block copolymer with 9 kg of cellulose acetate butyrate (CAB) evenly, and vacuum dry it at 70°C for 12 h in a vacuum drying oven. Then, melt, spin and draw it using a twin-screw melt spinning machine at 200°C to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber.

[0088] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 72 hours to extract cellulose acetate butyrate, thus obtaining thermoplastic block copolymer composite fiber; then the thermoplastic block copolymer composite fiber is dried at room temperature to obtain polymer nanofibers with an average diameter of 100 nm; wherein, the reflux temperature is 80 °C.

[0089] S4. The polymer nanofibers are kept in a vacuum at 120°C for 8 hours to obtain heat-treated polymer nanofibers.

[0090] S5. Place 10g of the heat-treated polymer nanofibers in mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0091] The mixed solution A is a mixture of undesirable solvent I, catalyst, and crosslinking agent; the catalyst is ferric chloride; the crosslinking agent is dimethoxymethane; and the undesirable solvent I is dimethyl sulfoxide.

[0092] The specific process of the pre-crosslinking treatment in step S5 is as follows: at 80°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 60 min; then the heat-treated polymer nanofibers are dried at 60°C under normal pressure and volatilized until the heat-treated polymer nanofibers maintain a constant weight to obtain pre-crosslinked block copolymer nanofibers.

[0093] S6. At 25°C, the pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 300 min. After swelling, a catalyst is added, and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with an average diameter of 150 nm and a fractal structure with a mirror-symmetric trumpet-shaped mouth (wherein the pores are composed of macropores-mesopores-micropores).

[0094] The undesirable solvent II is 1,2-dichloroethane; the crosslinking agent is dimethoxymethane; and the catalyst is ferric chloride.

[0095] S7. Under the action of high-speed shear force, 5g of the porous polymer nanofibers with fractal structure are dispersed in 500g of solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on a surface with an area of ​​2m². 2 Density is 30g / m³ 2 A 10μm thick coating is applied to the surface of a PA6 (nylon 6) spunbond nonwoven fabric substrate and dried in a fume hood to obtain a composite membrane containing porous polymer nanofibers. The nonwoven fabric substrate is then removed to obtain a membrane material with a double helix structure containing porous polymer nanofibers.

[0096] The porous polymer nanofibers with fractal structure are dispersed in solvent III at a concentration of 15 g / L; the coating weight is 10 g / m³. 2 Solvent Ⅲ is a mixture of water and acetone in a mass ratio of 1:1.

[0097] Example 4

[0098] Example 4 provides a membrane material containing porous polymer nanofibers and its preparation method, specifically including the following steps:

[0099] S1. Hydroxylated polystyrene and polyethyl methacrylate monomers are subjected to block copolymerization to obtain a thermoplastic block copolymer;

[0100] S2. Mix 2.5 kg of the thermoplastic block copolymer with 2.5 kg of cellulose acetate butyrate (CAB) evenly, and vacuum dry it at 70°C for 12 h in a vacuum drying oven. Then, melt, spin and draw it using a twin-screw melt spinning machine at 190°C to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber.

[0101] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 72 hours to extract cellulose acetate butyrate, thus obtaining thermoplastic block copolymer composite fiber; then the thermoplastic block copolymer composite fiber is dried at room temperature to obtain polymer nanofibers with an average diameter of 500 nm; wherein the reflux temperature is 90℃.

[0102] S4. After placing the polymer nanofibers in a vacuum at 100°C for 8 hours, heat-treated polymer nanofibers with an average diameter of 500 nm are obtained.

[0103] S5. Place 10g of the heat-treated polymer nanofibers in mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0104] The mixed solution A is a mixture of undesirable solvent I, catalyst, and crosslinking agent; the catalyst is ferric chloride; the crosslinking agent is dimethoxymethane; and the undesirable solvent I is dimethyl sulfoxide.

[0105] The specific process of the pre-crosslinking treatment in step S5 is as follows: at 80°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 70 min; then the heat-treated polymer nanofibers are placed at 30°C and dried under normal pressure to volatilize until the heat-treated polymer nanofibers maintain a constant weight, thus obtaining pre-crosslinked block copolymer nanofibers.

[0106] S6. At 25°C, the pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 240 min. After swelling, a catalyst is added and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with a fractal structure of 200 nm in average diameter (wherein the pores are composed of macropores-mesopores-micropores) and an average pore distance of 50 nm.

[0107] The good solvent II is 1,2-dichloroethane; the crosslinking agent includes dimethoxymethane; the catalyst is ferric chloride;

[0108] S7. Under the action of high-speed shear force, 10g of the porous polymer nanofibers with fractal structure are dispersed in 500g of solvent III to form a nanofiber dispersion, and then the nanofiber dispersion is coated on a surface with an area of ​​2m². 2 Density is 60 g / m³ 2 A 10μm thick coating is applied to the surface of a PP (polypropylene) meltblown nonwoven fabric substrate and dried in a fume hood to obtain a composite membrane containing porous polymer nanofibers. The nonwoven fabric substrate is then removed to obtain a membrane material containing porous polymer nanofibers with a multi-layer coaxial cylindrical structure.

[0109] The porous polymer nanofibers with fractal structures are dispersed in solvent III at a concentration of 20 g / L; the coating weight is 8 g / m³. 2 Solvent Ⅲ is a mixture of ethanol and acetone in a mass ratio of 1:2.

[0110] Example 5

[0111] Example 5 provides a membrane material containing porous polymer nanofibers and its preparation method, specifically including the following steps:

[0112] S1. Hydroxylated polystyrene, butadiene and polystyrene monomers are subjected to block copolymerization to obtain thermoplastic block copolymers;

[0113] S2. Mix 3 kg of the thermoplastic block copolymer with 10 kg of cellulose acetate butyrate (CAB) evenly, and vacuum dry it at 70°C for 12 h in a vacuum drying oven. Then, melt, spin and draw it using a twin-screw melt spinning machine at 170°C to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber.

[0114] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 72 hours to extract cellulose acetate butyrate, thereby obtaining thermoplastic block copolymer composite fiber; then the thermoplastic block copolymer composite fiber is dried at room temperature to obtain polymer nanofibers; wherein, the reflux temperature is 80℃.

[0115] S4. After placing the polymer nanofibers in a vacuum at 100°C for 8 hours, heat-treated polymer nanofibers with an average diameter of 700 nm are obtained.

[0116] S5. Place 10g of the heat-treated polymer nanofibers in mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0117] The mixed solution A is a mixture of undesirable solvent I, catalyst, and crosslinking agent; the catalyst is ferric chloride; the crosslinking agent is dimethoxymethane; and the undesirable solvent I is acetic acid.

[0118] The specific process of the pre-crosslinking treatment in step S5 is as follows: at 80°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 60 min; then the heat-treated polymer nanofibers are placed at 30°C and dried under normal pressure to volatilize until the heat-treated polymer nanofibers maintain a constant weight, thus obtaining pre-crosslinked block copolymer nanofibers.

[0119] S6. At 25°C, the pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 300 min. After swelling, a catalyst is added and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with an average diameter of 800 nm and a fractal structure with a core-skin structure (wherein the pores are composed of macropores-mesopores-micropores). The average pore size of the core-skin structure is 60 nm, and the specific morphology is as follows. Figure 1As shown;

[0120] The good solvent II is dichloromethane; the crosslinking agent is dimethoxymethane; the catalyst is ferric chloride;

[0121] S7. Under the action of high-speed shear force, 20g of the porous polymer nanofibers with fractal structure are dispersed in 500g of solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on a surface with an area of ​​2m². 2 Density is 20 g / m³ 2 A 10μm thick coating is applied to the surface of a PP (polypropylene) meltblown nonwoven fabric substrate and dried in a fume hood to obtain a composite membrane containing porous polymer nanofibers. The nonwoven fabric substrate is then removed to obtain a membrane material with a core-skin structure containing porous polymer nanofibers.

[0122] The porous polymer nanofibers with fractal structure are dispersed in solvent III at a concentration of 10 g / L; the coating weight is 8 g / m³. 2 Solvent Ⅲ is a mixture of ethanol and acetone in a mass ratio of 1:1.

[0123] In addition, a nanofiber membrane was prepared by electrospinning of three monomers: hydroxylated polystyrene, butadiene, and polystyrene. Its morphology is as follows: Figure 2 As shown in the figure. The prepared nanofiber membrane was then placed in a mixed solution of good solvent II and crosslinking agent to swell for 300 min. After swelling, a catalyst was added to carry out a hypercrosslinking reaction at 80℃. The morphology of the final nanofibers is shown in the figure. Figure 3 As shown. The good solvent II is dichloromethane; the crosslinking agent is dimethoxymethane; and the catalyst is ferric chloride. Compared with the prepared fractal-structured porous polymer nanofibers, it is clear that there are no obvious pores.

[0124] Example 6

[0125] This embodiment provides a method for preparing a membrane material containing porous polymer nanofibers, specifically including the following steps:

[0126] S1. A block copolymerization reaction is carried out on three monomers: 4-hydroxystyrene, β-polyglycidyl methacrylate, and β-poly4-aminostyrene to obtain a thermoplastic block copolymer.

[0127] S2. Mix 1 kg of the thermoplastic block copolymer with 12 kg of cellulose acetate butyrate (CAB) evenly, and vacuum dry it at 70°C for 12 h in a vacuum drying oven. Then, melt, spin and draw it using a twin-screw melt spinning machine at 210°C to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber.

[0128] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 72 hours to extract cellulose acetate butyrate, thus obtaining thermoplastic block copolymer composite fiber; then the thermoplastic block copolymer composite fiber is dried at room temperature to obtain polymer nanofibers; wherein, the reflux temperature is 65℃.

[0129] S4. After placing the polymer nanofibers in a vacuum at 150°C for 5 hours, heat-treated polymer nanofibers with an average diameter of 60 nm are obtained.

[0130] S5. Place 10g of the heat-treated polymer nanofibers in mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0131] The mixed solution A is a mixture of undesirable solvent I, catalyst, and crosslinking agent; the catalyst is zinc chloride; the crosslinking agent is dimethoxymethane; and the undesirable solvent I is acetic acid.

[0132] The specific process of the pre-crosslinking treatment in step S5 is as follows: at 80°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 60 min; then the heat-treated polymer nanofibers are placed at 30°C and dried under normal pressure to volatilize until the heat-treated polymer nanofibers maintain a constant weight, thus obtaining pre-crosslinked block copolymer nanofibers.

[0133] S6. At 25°C, the pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 300 min. After swelling, a catalyst is added and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with an average diameter of 90 nm and a fractal structure with a honeycomb structure (wherein the pores are composed of macropores-mesopores-micropores), wherein the average pore size of the honeycomb structure is 5 nm.

[0134] The good solvent II is dichloromethane; the crosslinking agent includes dimethoxymethane; the catalyst is ferric chloride;

[0135] S7. Under the action of high-speed shear force, 5g of the porous polymer nanofibers with fractal structure are dispersed in 250g of solvent III to form a nanofiber dispersion, and then the nanofiber dispersion is coated on a surface with an area of ​​2m². 2 Density is 60 g / m³ 2 A 2.5 μm thick coating is applied to the upper and lower surfaces of a PET meltblown nonwoven fabric substrate. After drying at room temperature, a composite membrane containing porous polymer nanofibers is obtained. The nonwoven fabric substrate is then removed, resulting in a membrane material with a honeycomb structure containing porous polymer nanofibers.

[0136] The porous polymer nanofibers with fractal structure are dispersed in solvent III at a concentration of 10 g / L; the coating weight is 10 g / m³. 2 Solvent Ⅲ is a mixture of water and acetone in a mass ratio of 1:1.

[0137] Example 7

[0138] This embodiment provides a method for preparing a membrane material containing porous polymer nanofibers, specifically including the following steps:

[0139] S1. A block copolymerization reaction is carried out between 4-hydroxystyrene and β-poly(N-isopropylacrylamide) monomers to obtain a thermoplastic block copolymer.

[0140] S2. Mix 2 kg of the thermoplastic block copolymer with 12 kg of cellulose acetate butyrate (CAB) evenly, and vacuum dry it at 70°C for 12 h in a vacuum drying oven. Then, melt, spin and draw it using a twin-screw melt spinning machine at 220°C to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber.

[0141] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 72 hours to extract cellulose acetate butyrate, thus obtaining thermoplastic block copolymer composite fiber; then the thermoplastic block copolymer composite fiber is dried at room temperature to obtain polymer nanofibers; wherein, the reflux temperature is 85℃.

[0142] S4. After placing the polymer nanofibers in argon gas at 140°C for 5 hours, heat-treated polymer nanofibers with an average diameter of 80 nm are obtained.

[0143] S5. Place 10g of the heat-treated polymer nanofibers in mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0144] The mixed solution A is a mixture of undesirable solvent I, catalyst, and crosslinking agent; the catalyst is zinc chloride; the crosslinking agent is dimethoxymethane; and the undesirable solvent I is acetic acid.

[0145] The specific process of the pre-crosslinking treatment in step S5 is as follows: at 80°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 70 min; then the heat-treated polymer nanofibers are placed at 30°C and dried under normal pressure to volatilize until the heat-treated polymer nanofibers maintain a constant weight, thus obtaining pre-crosslinked block copolymer nanofibers.

[0146] S6. At 25°C, the pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 300 min. After swelling, a catalyst is added and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with an average diameter of 100 nm and a fractal structure with irregular protrusions on the surface (wherein the pores are composed of macropores-mesopores-micropores), and the average size of the irregular protrusions on the surface is 12 nm.

[0147] The good solvent II is 1,2-dichloroethane; the crosslinking agent is dimethoxymethane; and the catalyst is ferric chloride.

[0148] S7. Under the action of high-speed shear force, 20g of the porous polymer nanofibers with fractal structure are dispersed in 500g of solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on a surface with an area of ​​2m². 2 Density is 20 g / m³ 2 A 10μm thick coating is applied to the surface of a PE film and dried at room temperature to obtain a porous polymer nanofiber composite membrane with a surface protrusion structure. The PE film is then removed to obtain a membrane material with a porous polymer nanofiber structure.

[0149] The porous polymer nanofibers with fractal structures are dispersed in solvent III at a concentration of 10 g / L; the coating weight is 15 g / m³. 2 Solvent Ⅲ is a mixture of water and ethanol in a mass ratio of 1:1.

[0150] Example 8

[0151] This embodiment provides a method for preparing a membrane material containing porous polymer nanofibers, specifically including the following steps:

[0152] S1. A block copolymerization reaction is carried out on three monomers: poly(p-chloromethylstyrene), glycidyl methacrylate, and 2-vinylpyridine to obtain a thermoplastic block copolymer.

[0153] S2. Mix 3 kg of the thermoplastic block copolymer with 10 kg of cellulose acetate butyrate (CAB) evenly, and vacuum dry it at 70°C for 12 h in a vacuum drying oven. Then, melt, spin and draw it using a twin-screw melt spinning machine at 170°C to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber.

[0154] S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is refluxed in acetone for 72 hours to extract cellulose acetate butyrate, thereby obtaining thermoplastic block copolymer composite fiber; then the thermoplastic block copolymer composite fiber is dried at room temperature to obtain polymer nanofibers; wherein, the reflux temperature is 80℃.

[0155] S4. After placing the polymer nanofibers in a vacuum at 100°C for 8 hours, heat-treated polymer nanofibers with an average diameter of 300 nm are obtained.

[0156] S5. Place 10g of the heat-treated polymer nanofibers in mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers.

[0157] The mixed solution A is a mixture of undesirable solvent I, catalyst, and crosslinking agent; the catalyst is ferric chloride; the crosslinking agent is dimethoxymethane; and the undesirable solvent I is acetic acid.

[0158] The specific process of the pre-crosslinking treatment in step S5 is as follows: at 80°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 60 min; then the heat-treated polymer nanofibers are placed at 30°C and dried under normal pressure to volatilize until the heat-treated polymer nanofibers maintain a constant weight, thus obtaining pre-crosslinked block copolymer nanofibers.

[0159] S6. At 25°C, the pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent to swell for 300 min. After swelling, a catalyst is added, and a hypercrosslinking reaction is carried out at 80°C to obtain porous polymer nanofibers with an average diameter of 400 nm and a fractal structure with a core-skin structure (wherein the pores are composed of macropores-mesopores-micropores), and the average pore size of the core-skin structure is 60 nm.

[0160] The good solvent II is 1,2-dichloroethane; the crosslinking agent is dimethoxymethane; and the catalyst is ferric chloride.

[0161] S7. Under the action of high-speed shear force, 20g of the porous polymer nanofibers with fractal structure are dispersed in 500g of solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on a surface with an area of ​​2m². 2 Density is 20 g / m³ 2 A 15μm thick coating is applied to the surface of a PP (polypropylene) film and dried in a fume hood to obtain a porous polymer nanofiber composite membrane. The film is then removed to obtain a membrane material with a core-skin structure containing porous polymer nanofibers.

[0162] The porous polymer nanofibers with fractal structure are dispersed in solvent III at a concentration of 10 g / L; the coating weight is 8 g / m³. 2 Solvent Ⅲ is a mixture of ethanol and acetone in a mass ratio of 1:1.

[0163] In summary, this invention provides a membrane material containing porous polymer nanofibers and its preparation method. Based on mature melt phase separation technology for large-scale nanofiber preparation, a thermoplastic block copolymer is blended with cellulose acetate butyrate (CAB) to form a thermodynamically incompatible system. During melt spinning, the thermoplastic block copolymer undergoes phase separation and self-assembly under the coupled effects of multiple fields such as temperature, phase boundary, shear force, and tensile force. This achieves the construction of the secondary physical structure of the nanofibers themselves while forming fibers, providing a rapid and efficient preparation method for nanofiber membranes with hierarchical structures. The fibers undergo self-crosslinking and pore formation via Friedel-Crafts reaction (i.e., self-assembly of polymer nanofibers induced by selective solvent heat treatment). The nanofibers prepared in this way possess a hierarchical pore structure, and the prepared porous nanofiber membrane has the advantages of ultra-high specific surface area and high porosity. Furthermore, it can be dispersed in a certain solvent to achieve batch film formation, overcoming the technical bottleneck of existing methods that struggle to simultaneously achieve the preparation of nanofibers and nanofiber membranes with hierarchical pore structures. Furthermore, because the polymer components used contain a variety of active functional groups, the resulting porous polymer nanofiber membrane materials are easily subjected to various forms of functionalization modification, greatly expanding the application fields of nanofiber membranes. Therefore, they show significant application potential in media filtration and purification, affinity separation and purification, membrane catalysis, bioelectronic sensing, biomedicine, and medical fields.

[0164] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a membrane material containing porous polymer nanofibers, characterized in that, Includes the following steps: S1. Two or more different monomers are subjected to block copolymerization to obtain thermoplastic block copolymers; S2. After uniformly mixing the thermoplastic block copolymer with cellulose acetate butyrate, the mixture is melted, spun, and drawn to obtain thermoplastic block copolymer / cellulose acetate butyrate composite fiber. S3. The thermoplastic block copolymer / cellulose acetate butyrate composite fiber is placed in acetone and refluxed to extract cellulose acetate butyrate, thereby obtaining thermoplastic block copolymer composite fiber; the thermoplastic block copolymer composite fiber is then dried to obtain polymer nanofibers. S4. The polymer nanofibers are subjected to heat treatment under vacuum or inert gas to obtain heat-treated polymer nanofibers. S5. The heat-treated polymer nanofibers are placed in a mixed solution A for pre-crosslinking treatment to obtain pre-crosslinked block copolymer nanofibers. S6. The pre-crosslinked block copolymer nanofibers are placed in a mixed solution of good solvent II and crosslinking agent for swelling. After swelling, a catalyst is added to carry out a hypercrosslinking reaction, thereby obtaining porous polymer nanofibers with fractal structure. S7. The porous polymer nanofibers with fractal structure are dispersed in solvent III to form a nanofiber dispersion. The nanofiber dispersion is then coated on the surface of a substrate. After drying, the substrate is removed to obtain a membrane material containing porous polymer nanofibers. In step S5, the mixed solution A comprises a mixed solution consisting of a poor solvent I, a catalyst, and a crosslinking agent; the catalyst comprises one of ferric chloride and zinc chloride; the crosslinking agent comprises dimethoxymethane; and the poor solvent I comprises one or more of acetic acid and dimethyl sulfoxide. The specific process of the pre-crosslinking treatment in step S5 is as follows: at 70-90°C, the heat-treated polymer nanofibers are placed in mixed solution A and reacted for 1-80 minutes; then the heat-treated polymer nanofibers are dried at 10-110°C under normal pressure until the heat-treated polymer nanofibers maintain a constant weight, thus obtaining pre-crosslinked block copolymer nanofibers. In step S6, the good solvent II includes one or more of 1,2-dichloroethane, dichloromethane, and chloroform; the crosslinking agent includes dimethoxymethane; the catalyst includes one of ferric chloride and zinc chloride; the swelling temperature is 20-30°C, and the swelling time is 1-300 min; Solvent III comprises two or more of the following: water, tetrahydrofuran, ethanol, acetone, and N,N-dimethylformamide.

2. The method for preparing the membrane material containing porous polymer nanofibers according to claim 1, characterized in that: In step S1, the monomer includes one of ethylene glycol, monomethyl ether polyoxyethylene, hydroxylated polystyrene, glycidyl methacrylate, 2-vinylpyridine, 4-vinylpyridine, acrylamide, 4-aminostyrene, 4-hydroxystyrene, p-chloromethylstyrene, acrylic acid, N-isopropylacrylamide, and ethylene oxide.

3. The method for preparing the membrane material containing porous polymer nanofibers according to claim 1, characterized in that: In step S2, the mass percentage of the thermoplastic block copolymer to the cellulose acetate butyrate is 5-50:50-95.

4. The method for preparing the membrane material containing porous polymer nanofibers according to claim 1, characterized in that: In step S3, the reflux temperature is 60℃~90℃, the reflux time is 24~72h, and the diameter of the obtained polymer nanofibers is 50~1000nm.

5. The method for preparing membrane materials containing porous polymer nanofibers according to claim 1, characterized in that: In step S4, the heat treatment is carried out at a temperature of 50 to 300°C for 1 to 24 hours, and the inert gas includes one of nitrogen and argon.

6. The method for preparing the membrane material containing porous polymer nanofibers according to claim 1, characterized in that: In step S7, the concentration of the porous polymer nanofibers with fractal structure dispersed in solvent III is 0.5–2.0 g / L; the coating basis weight is 0.5–100 g / m³. 2 .

7. The membrane material containing porous polymer nanofibers prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The average diameter of the nanofibers in the membrane material containing porous polymer nanofibers is 50–1000 nm; the membrane material containing porous polymer nanofibers has a hierarchical pore structure; the average diameter of the nanofibers in the membrane material containing porous polymer nanofibers is greater than the average pore diameter of the hierarchical pore structure.

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