Asymmetric hydrophilic and hydrophobic anion exchange membrane and preparation method thereof

Abstract

The present invention belongs to the technical field of fuel cell materials, and particularly relates to a method for preparing an asymmetric hydrophilic-hydrophobic anion exchange membrane. The method comprises two steps: preparing a hydrophobic layer and preparing a hydrophilic layer. The prepared asymmetric hydrophilic-hydrophobic anion exchange membrane has hydrophilic and hydrophobic properties on both sides, respectively. The hydrophilic portion facilitates water retention and prevents drying out of the cathode; the hydrophobic portion facilitates drainage and prevents flooding of the anode. This improves the water transport capacity of the membrane at high current density, which is beneficial for water management. In addition, by adjusting the hydrophilicity and hydrophobicity of the cross-linking agent, the hydrophilic-hydrophobic properties on both sides of the membrane can be adjusted, making the asymmetric hydrophilic-hydrophobic anion exchange membrane more applicable. It has broad application prospects in the field of anion exchange membrane fuel cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell materials, and in particular relates to an asymmetric hydrophilic and hydrophobic anion exchange membrane and a preparation method thereof. Background Art

[0002] Fuel cells are clean conversion devices that directly convert chemical energy into electrical energy. They offer advantages such as being green, pollution-free, sustainable, and highly efficient. Because the oxygen reduction reaction (ORR) exhibits faster kinetics under alkaline conditions, alkaline anion exchange membrane fuel cells (HEMFCs) can utilize non-precious metals as electrocatalysts, significantly reducing costs and attracting widespread attention.

[0003] Among HEMFC components, the anion exchange membrane (HEM) is one of the key materials that limits HEMFC performance and lifespan. Particularly at high current densities, the HEMFC anode rapidly produces water, causing anode flooding; while the cathode rapidly consumes water, leading to cathode dryout. These two negative effects collectively reduce HEMFC efficiency and lifespan. In recent years, many researchers have attempted to adjust the water content in the HEM through inorganic material doping (CN108164723B), hydrophilic modification (DE102016007815A1), and hydrophobic modification (KR101766577B1). These methods only impart a single hydrophilic or hydrophobic property to the membrane, making it difficult to balance the water content of the anode and cathode in practical applications. This leads to an imbalance in the water content between the anode and cathode, ultimately causing a rapid decline in HEMFC performance. Therefore, it is necessary to design HEM preparation methods that possess an asymmetric hydrophilic and hydrophobic structure to adapt to the different water environments at the anode and cathode. Therefore, it is necessary to design an asymmetric hydrophilic and hydrophobic anion exchange membrane to address these issues. Summary of the Invention

[0004] Currently, anion exchange membrane fuel cells (ANEMFs) are susceptible to anode dry-out and cathode flooding at high current densities, resulting in reduced fuel cell performance and efficiency at high current densities. One objective of the present invention is to prepare an asymmetric hydrophilic anion exchange membrane, imparting hydrophobic and hydrophilic properties to both sides of the membrane. A second objective of the present invention is to create a significant difference in water affinity between the hydrophilic and hydrophobic portions of the anion exchange membrane, thereby creating a difference in water chemical potential within the membrane and promoting water diffusion from the hydrophobic to the hydrophilic side of the membrane.

[0005] In order to achieve the above purpose, the technical solutions are as follows:

[0006] An asymmetric hydrophilic and hydrophobic anion exchange membrane has a two-layer structure, including a hydrophobic layer and a hydrophilic layer. The general structural formula is shown below:

[0007]

[0008] C1 is a hydrophobic crosslinker; C2 is a hydrophilic crosslinker.

[0009] The hydrophobic layer is formed by reacting a polymer containing a cross-linkable functional group with a hydrophobic cross-linking agent; the hydrophilic layer is formed by reacting a polymer containing a cross-linkable functional group with a hydrophilic cross-linking agent; the polymer containing a cross-linkable functional group has a general structural formula as shown below:

[0010]

[0011] The main chain Ar is polyphenylene ether, polysulfone, polyetheretherketone, polyarylpiperidine, etc.

[0012] The general structural formula of polyarylpiperidine is shown below:

[0013]

[0014] Functional group F is the following structure:

[0015]

[0016] Based on the above technical solution, preferably, the hydrophobic layer uses a hydrophobic crosslinking agent C1, and its general structural formula is as follows:

[0017]

[0018] The substituent X is the following structure:

[0019]

[0020] The structure of the hydrophilic layer is consistent with the polymer structure of the cross-linkable reaction functional group. The hydrophilic layer uses a hydrophilic cross-linking agent C2, and its general structure is shown in the figure:

[0021]

[0022] The substituent X is the following structure:

[0023]

[0024] A method for preparing an asymmetric hydrophilic and hydrophobic anion exchange membrane comprises the following steps (the steps are not in particular order):

[0025] (1) Preparation of hydrophobic layer

[0026] Dissolve the aromatic polymer with functional groups in a good solvent and add a hydrophobic crosslinker in a certain proportion. Control the reaction temperature at 30-100°C and allow the crosslinking reaction to proceed for 24 hours. After the reaction is complete, a hydrophobically modified crosslinked polymer solution is obtained. The hydrophobically modified crosslinked polymer solution is then poured into a mold and dried at 80-120°C to form a film, thereby obtaining a hydrophobically modified crosslinked anion exchange membrane (note that demolding is not performed).

[0027] (2) Preparation of hydrophilic layer

[0028] The same aromatic polymer with functional groups is dissolved in a good solvent and a hydrophilic crosslinker is added in a specific proportion. The reaction temperature is controlled at 30-100°C and the crosslinking reaction is carried out for 24 hours. After completion of the reaction, a hydrophilically modified crosslinked polymer solution is obtained. The hydrophilically modified crosslinked polymer solution is then poured into a mold containing a hydrophobically modified crosslinked anion exchange membrane. The solution is then incubated at 30-60°C for 2 hours and then dried at 80-120°C to form a membrane, resulting in an asymmetric hydrophilic-hydrophobic anion exchange membrane.

[0029] Based on the above technical solution, preferably, the main chain of the hydrophobic layer polymer is an aromatic polymer, including polyphenylene ether, polysulfone, polyetheretherketone, polyarylpiperidine, etc.

[0030] Based on the above technical solution, preferably, the functional group of the hydrophobic layer polymer is tertiary amino, piperidinyl, halogen, etc.

[0031] Based on the above technical solution, preferably, the hydrophobic crosslinking agent is a dihalogenated alkane, including 1,2-diiodoethane, 1,3-diiodopropane, 1,6-diiodohexane, etc.

[0032] Based on the above technical solution, preferably, the main chain of the hydrophilic layer polymer is an aromatic polymer, including polyphenylene ether, polysulfone, polyetheretherketone, polyarylpiperidine, etc.

[0033] Based on the above technical solution, preferably, the functional group of the hydrophilic layer polymer is tertiary amino, piperidinyl, halogen, etc.

[0034] Based on the above technical solution, preferably, the hydrophilic crosslinking agent is a dihalogenated alkane containing an ether bond, including 2,2'-dibromodiethyl ether, brominated-triethylene glycol-bromo, 1,14-dibromo-3,6,9,12-tetraoxatetradecane, and the like.

[0035] Based on the above technical solution, preferably, in the preparation step (1) of preparing the hydrophobic layer, the molar ratio of the hydrophobic crosslinking agent to the polymer is (1-10):1.

[0036] Based on the above technical solution, preferably, in the preparation of the hydrophilic layer in step (2), the molar ratio of the hydrophilic crosslinking agent to the polymer is (1-10):1.

[0037] Beneficial effects

[0038] (1) The asymmetric hydrophilic-hydrophobic anion exchange membrane of the present invention has a hydrophilic portion and a hydrophobic portion. The hydrophobic portion is used on the anode side of the fuel cell, which reduces the binding force of water in the membrane and makes it easier for water to be carried away by gas, which is beneficial for drainage and inhibiting flooding. The hydrophilic portion is used on the cathode side of the fuel cell, which increases the membrane's ability to bind water, facilitates the adsorption and binding of water, and is beneficial for water retention and alleviates dryness.

[0039] (2) The asymmetric hydrophilic and hydrophobic anion exchange membrane of the present invention can form a chemical potential gradient field of water in the membrane through the hydrophilic part and the hydrophobic part, thereby promoting the diffusion of water from the hydrophobic side to the hydrophilic side, and further improving the dryness and flooding of the cathode and anode from the inside of the membrane; improving the water transmission capacity of the membrane at high current density, which is beneficial to water management.

[0040] (3) The asymmetric hydrophilic-hydrophobic anion exchange membrane of the present invention utilizes a crosslinking method to increase the mechanical strength and dimensional stability of the membrane. The crosslinking agent employed is both flexible and chemically stable. The flexibility enhances the entanglement and kinking between polymer chains, improving mechanical properties, while the chemical stability allows for adaptation to the strong alkaline environment of alkaline fuel cells.

[0041] (4) The asymmetric hydrophilic and hydrophobic anion exchange membrane of the present invention can adjust the hydrophilic and hydrophobic properties on both sides of the membrane by adjusting the hydrophilic and hydrophobic properties of the crosslinking agent, making the asymmetric hydrophilic and hydrophobic anion exchange membrane more applicable. It has broad application prospects in the field of anion exchange membrane fuel cells.

[0042] (5) In the asymmetric hydrophilic and hydrophobic anion exchange membrane of the present invention, the synergistic effect of the crosslinking agent and the ratio can increase the mutual compatibility of the hydrophilic and hydrophobic layers and improve the film forming properties.

[0043] (6) The thickness of the hydrophilic layer and the hydrophobic layer of the asymmetric hydrophilic-hydrophobic anion exchange membrane of the present invention can be adjusted by adjusting the amount of the casting solution added. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the structure of the asymmetric hydrophilic and hydrophobic anion exchange membrane of the present invention.

[0045] Figure 2 This is the nuclear magnetic resonance spectrum of the asymmetric hydrophilic and hydrophobic anion exchange membrane polymer main chain in Example 1.

[0046] Figure 3 This is a contact angle diagram of the hydrophobic side of the asymmetric hydrophilic-hydrophobic anion exchange membrane of Example 1 with water in air.

[0047] Figure 4This is a contact angle diagram of the hydrophilic side of the asymmetric hydrophilic-hydrophobic anion exchange membrane of Example 1 with water in air.

[0048] Figure 5 This is a contact angle diagram of the hydrophobic side of the asymmetric hydrophilic-hydrophobic anion exchange membrane of Example 2 with water in air.

[0049] Figure 6 This is a contact angle diagram of the hydrophilic side of the asymmetric hydrophilic-hydrophobic anion exchange membrane of Example 2 with water in air.

[0050] Figure 7 This is a contact angle diagram of the hydrophobic side of the asymmetric hydrophilic-hydrophobic anion exchange membrane of Example 3 with water in air.

[0051] Figure 8 This is a contact angle diagram of the hydrophilic side of the asymmetric hydrophilic-hydrophobic anion exchange membrane of Example 3 with water in air.

[0052] Figure 9 This is an optical picture of the asymmetric hydrophilic and hydrophobic anion exchange membrane after drying in Example 1.

[0053] Figure 10 This is an optical picture of the asymmetric hydrophilic and hydrophobic anion exchange membrane in Comparative Example 1 after drying. DETAILED DESCRIPTION

[0054] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0055] Example 1

[0056] A method for preparing an asymmetric hydrophilic and hydrophobic anion exchange membrane is as follows:

[0057] (1) Synthesis of polyarylpiperidine polymers

[0058] Dispersing p-terphenyl and N-methyl-4-piperidone in dichloromethane and mechanically stirring to mix uniformly; the molar ratio of p-terphenyl to N-methyl-4-piperidone is 1:1; the molar ratio of dichloromethane to N-methyl-4-piperidone is 20:1; slowly adding trifluoromethanesulfonic acid dropwise through a constant pressure funnel, controlling the reaction temperature to 0°C, and conducting the polymerization reaction for 8-24 hours, wherein the product gradually becomes viscous until mechanical stirring becomes very difficult and the reaction is stopped; the molar ratio of trifluoromethanesulfonic acid to p-terphenyl is 10:1; removing the polymer from the reaction vessel using a tetrafluoroethylene spoon, washing with a large amount of saturated potassium carbonate solution until neutral, and vacuum drying at 80°C to obtain a yellow-white polyarylpiperidine polymer;

[0059] (2) Preparation of hydrophobic layer

[0060] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; 1,2-diiodoethane is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of 1,2-diiodoethane to the polyaryl piperidine polymer is 5:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophobically modified cross-linked polymer solution is obtained; 10 ml of the hydrophobically modified cross-linked polymer solution is pipetted into a 10 cm×10 cm glass mold by a pipette, and dried at 80°C to form a film to obtain a hydrophobically modified cross-linked anion exchange membrane (note that demolding is not performed);

[0061] (3) Preparation of hydrophilic layer

[0062] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; 2,2'-dibromodiethyl ether is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of 2,2'-dibromodiethyl ether to the polyaryl piperidine polymer is 5:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophilic-modified cross-linked polymer solution is obtained; in the mold containing the hydrophobic-modified cross-linked anion exchange membrane in step (2), 10 ml of the hydrophilic-modified cross-linked polymer solution is transferred using a pipette, and the solution is kept at 60°C for 2 hours, and then dried at 80°C to form a film, thereby obtaining an asymmetric hydrophilic-hydrophobic anion exchange membrane; as can be seen from the optical image, the membrane has a uniform, transparent and flat morphology; and the contact angle test shows that the hydrophilic side contact angle is 85.27° and the hydrophobic side contact angle is 91.81°.

[0063] Example 2

[0064] A method for preparing an asymmetric hydrophilic and hydrophobic anion exchange membrane is as follows:

[0065] (1) Synthesis of polyarylpiperidine polymers

[0066] Dispersing p-terphenyl and N-methyl-4-piperidone in dichloromethane and mechanically stirring to mix uniformly; the molar ratio of dichloromethane to N-methyl-4-piperidone is 20:1; the molar ratio of p-terphenyl to N-methyl-4-piperidone is 1:1; slowly adding trifluoromethanesulfonic acid dropwise through a constant pressure funnel, and controlling the reaction temperature to 0°C. The polymerization reaction is carried out for 8-24 hours, and the product gradually becomes viscous until mechanical stirring becomes very difficult and the reaction is stopped; the molar ratio of trifluoromethanesulfonic acid to p-terphenyl is 10:1; removing the polymer from the reaction vessel with a tetrafluoroethylene spoon, washing with a large amount of saturated potassium carbonate solution until neutral, and vacuum drying at 80°C to obtain a yellow-white polyarylpiperidine polymer;

[0067] (2) Preparation of hydrophobic layer

[0068] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; 1,3-diiodopropane is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of 1,3-diiodopropane to the polyaryl piperidine polymer is 5:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophobically modified cross-linked polymer solution is obtained; 10 ml of the hydrophobically modified cross-linked polymer solution is pipetted into a 10 cm×10 cm glass mold by a pipette, and dried at 80°C to form a film to obtain a hydrophobically modified cross-linked anion exchange membrane (note that demolding is not performed);

[0069] (3) Preparation of hydrophilic layer

[0070] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; brominated-triethylene glycol-bromo is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of brominated-triethylene glycol-bromo and the polyaryl piperidine polymer is 5:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophilic-modified cross-linked polymer solution is obtained; in the mold containing the hydrophobic-modified cross-linked anion exchange membrane in step (2), 10 ml of the hydrophilic-modified cross-linked polymer solution is transferred using a pipette, and the solution is kept warm at 60°C for 2 hours, and then dried at 80°C to form a film to obtain an asymmetric hydrophilic-hydrophobic anion exchange membrane; and a contact angle test shows that the hydrophilic side contact angle is 79.25° and the hydrophobic side contact angle is 93.79°.

[0071] Example 3

[0072] A method for preparing an asymmetric hydrophilic and hydrophobic anion exchange membrane is as follows:

[0073] (1) Synthesis of polyarylpiperidine polymers

[0074] Dispersing p-terphenyl and N-methyl-4-piperidone in dichloromethane and mechanically stirring to mix uniformly; the molar ratio of dichloromethane to N-methyl-4-piperidone is 20:1; the molar ratio of p-terphenyl to N-methyl-4-piperidone is 1:1; slowly adding trifluoromethanesulfonic acid dropwise through a constant pressure funnel, and controlling the reaction temperature to 0°C. The polymerization reaction is carried out for 8-24 hours, and the product gradually becomes viscous until mechanical stirring becomes very difficult and the reaction is stopped; the molar ratio of trifluoromethanesulfonic acid to p-terphenyl is 10:1; removing the polymer from the reaction vessel with a tetrafluoroethylene spoon, washing with a large amount of saturated potassium carbonate solution until neutral, and vacuum drying at 80°C to obtain a yellow-white polyarylpiperidine polymer;

[0075] (2) Preparation of hydrophobic layer

[0076] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; 1,6-diiodohexane is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of 1,6-diiodohexane to the polyaryl piperidine polymer is 5:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophobically modified cross-linked polymer solution is obtained; 10 ml of the hydrophobically modified cross-linked polymer solution is pipetted into a 10 cm×10 cm glass mold by a pipette, and dried at 80°C to form a film to obtain a hydrophobically modified cross-linked anion exchange membrane (note that demolding is not performed);

[0077] (3) Preparation of hydrophilic layer

[0078] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; 1,14-dibromo-3,6,9,12-tetraoxatetradecane is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of 1,14-dibromo-3,6,9,12-tetraoxatetradecane to the polyaryl piperidine polymer is 5:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophilic-modified cross-linked polymer solution is obtained; in the mold containing the hydrophobic-modified cross-linked anion exchange membrane in step (2), 10 ml of the hydrophilic-modified cross-linked polymer solution is transferred using a pipette, and the solution is kept warm at 60°C for 2 hours, and then dried at 80°C to form a film, thereby obtaining an asymmetric hydrophilic-hydrophobic anion exchange membrane; and a contact angle test shows that the hydrophilic side contact angle is 65.38° and the hydrophobic side contact angle is 110.16°.

[0079] Example 4

[0080] A method for preparing an asymmetric hydrophilic and hydrophobic anion exchange membrane is as follows:

[0081] (1) Synthesis of polyarylpiperidine polymers

[0082] Dispersing p-terphenyl and N-methyl-4-piperidone in dichloromethane and mechanically stirring to mix uniformly; the molar ratio of dichloromethane to N-methyl-4-piperidone is 20:1; the molar ratio of p-terphenyl to N-methyl-4-piperidone is 1:1; slowly adding trifluoromethanesulfonic acid dropwise through a constant pressure funnel, and controlling the reaction temperature to 0°C. The polymerization reaction is carried out for 8-24 hours, and the product gradually becomes viscous until mechanical stirring becomes very difficult and the reaction is stopped; the molar ratio of trifluoromethanesulfonic acid to p-terphenyl is 10:1; removing the polymer from the reaction vessel with a tetrafluoroethylene spoon, washing with a large amount of saturated potassium carbonate solution until neutral, and vacuum drying at 80°C to obtain a yellow-white polyarylpiperidine polymer;

[0083] (2) Preparation of hydrophilic layer

[0084] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; 1,14-dibromo-3,6,9,12-tetraoxatetradecane is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of 1,14-dibromo-3,6,9,12-tetraoxatetradecane to the polyaryl piperidine polymer is 5:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophilically modified cross-linked polymer solution is obtained; 10 ml of the hydrophilically modified cross-linked polymer solution is pipetted into a 10 cm×10 cm glass mold by a pipette, and dried at 80°C to form a film to obtain a hydrophilically modified cross-linked anion exchange membrane (note that demolding is not performed);

[0085] (3) Preparation of hydrophobic layer

[0086] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; 1,6-diiodohexane is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of 1,6-diiodohexane to the polyaryl piperidine polymer is 5:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophobically modified cross-linked polymer solution is obtained; in the mold containing the hydrophilically modified cross-linked anion exchange membrane in step (2), 10 ml of the hydrophobically modified cross-linked polymer solution is transferred using a pipette, and the solution is kept warm at 60°C for 2 hours, and then dried at 80°C to form a film, thereby obtaining an asymmetric hydrophilic and hydrophobic anion exchange membrane.

[0087] Comparative Example 1

[0088] (1) Synthesis of polyarylpiperidine polymers

[0089] Dispersing p-terphenyl and N-methyl-4-piperidone in dichloromethane and mechanically stirring to mix uniformly; the molar ratio of dichloromethane to N-methyl-4-piperidone is 20:1; the molar ratio of p-terphenyl to N-methyl-4-piperidone is 1:1; slowly adding trifluoromethanesulfonic acid dropwise through a constant pressure funnel, and controlling the reaction temperature to 0°C. The polymerization reaction is carried out for 8-24 hours, and the product gradually becomes viscous until mechanical stirring becomes very difficult and the reaction is stopped; the molar ratio of trifluoromethanesulfonic acid to p-terphenyl is 10:1; removing the polymer from the reaction vessel with a tetrafluoroethylene spoon, washing with a large amount of saturated potassium carbonate solution until neutral, and vacuum drying at 80°C to obtain a yellow-white polyarylpiperidine polymer;

[0090] (2) Preparation of hydrophobic layer

[0091] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; iodomethyl dimethyl methoxy silane is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of iodomethyl dimethyl methoxy silane to the polyaryl piperidine polymer is 4:1; the reaction temperature is controlled at 80° C., and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophobically modified cross-linked polymer solution is obtained; the hydrophobically modified cross-linked polymer solution is added to a 10 cm×10 cm glass mold by a pipette gun, and dried at 80° C. to form a film to obtain a hydrophobically modified cross-linked anion exchange membrane (note that demolding is not performed);

[0092] (3) Preparation of hydrophilic layer

[0093] The polyaryl piperidine polymer prepared in step (1) is dissolved in dimethyl sulfoxide and dispersed by magnetic stirring; the molar ratio of the polyaryl piperidine polymer to dimethyl sulfoxide is 1:20; iodomethyl trimethoxysilane is accurately weighed using an electronic balance and added to the reaction system; the molar ratio of iodomethyl trimethoxysilane to the polyaryl piperidine polymer is 4:1; the reaction temperature is controlled at 80°C, and the cross-linking reaction is carried out for 24 hours. After the reaction is completed, a hydrophilic-modified cross-linked polymer solution is obtained; 10 ml of the hydrophilic-modified cross-linked polymer solution is transferred to the mold containing the hydrophobic-modified cross-linked anion exchange membrane in step (2) using a pipette, and the solution is kept warm at 60°C for 2 hours, and then dried at 80°C to form a film to obtain an asymmetric hydrophilic-hydrophobic anion exchange membrane; the asymmetric hydrophilic-hydrophobic anion exchange membrane is demoulded by immersing it in a saturated sodium bicarbonate solution at 80°C, and a large number of wrinkles and cracks are generated in the membrane after drying.

Claims

1. A method for preparing an asymmetric hydrophilic and hydrophobic anion exchange membrane, characterized in that: The steps include: (1) Preparation of hydrophobic layer The aromatic polymer with functional groups is dissolved in a good solvent, a hydrophobic crosslinking agent is added in a certain proportion, the reaction temperature is controlled at 30-100°C, and the crosslinking reaction is carried out for 24 hours. After the reaction is completed, a hydrophobically modified crosslinked polymer solution is obtained; the hydrophobically modified crosslinked polymer solution is then poured into a mold and dried at 80-120°C to form a film, thereby obtaining a hydrophobically modified crosslinked anion exchange membrane without demolding; (2) Preparation of hydrophilic layer The aromatic polymer with functional groups is dissolved in a good solvent, a hydrophilic crosslinking agent is added in a certain proportion, the reaction temperature is controlled at 30-100°C, and the crosslinking reaction is carried out for 24 hours. After the reaction is completed, a hydrophilic-modified crosslinked polymer solution is obtained; then, the hydrophilic-modified crosslinked polymer solution is poured into a mold containing a hydrophobic-modified crosslinked anion exchange membrane, and the solution is kept at 30-60°C for 2 hours, and then dried at 80-120°C to form a membrane, thereby obtaining an asymmetric hydrophilic-hydrophobic anion exchange membrane; The aromatic polymer with functional groups is prepared by the following method: Disperse p-terphenyl and N-methyl-4-piperidone in dichloromethane and mix uniformly with mechanical stirring; the molar ratio of p-terphenyl to N-methyl-4-piperidone is 1:1; the molar ratio of dichloromethane to N-methyl-4-piperidone is 20:1; slowly add trifluoromethanesulfonic acid dropwise through a constant pressure funnel, and control the reaction temperature to be 0°C. The polymerization reaction is carried out for 8-24 hours, and the product gradually becomes viscous until mechanical stirring becomes very difficult and the reaction is stopped; the molar ratio of trifluoromethanesulfonic acid to p-terphenyl is 10:1; remove the polymer from the reaction vessel with a tetrafluoroethylene spoon, wash with a large amount of saturated potassium carbonate solution until neutral, and vacuum dry at 80°C to obtain; The hydrophobic crosslinking agent is selected from 1,2-diiodoethane, 1,3-diiodopropane or 1,6-diiodohexane; The hydrophilic crosslinking agent is selected from 2,2'-dibromodiethyl ether, bromo-triethylene glycol-bromo or 1,14-dibromo-3,6,9,12-tetraoxatetradecane.

2. The method for preparing an asymmetric hydrophilic and hydrophobic anion exchange membrane according to claim 1, wherein: In step (1) of preparing the hydrophobic layer, the molar ratio of the hydrophobic crosslinking agent to the aromatic polymer with functional groups is 1-10:

1.

3. The method for preparing an asymmetric hydrophilic and hydrophobic anion exchange membrane according to claim 1, characterized in that: In step (2) of preparing the hydrophilic layer, the molar ratio of the hydrophilic cross-linking agent to the aromatic polymer with functional groups is 1-10:

1.

4. The asymmetric hydrophilic and hydrophobic anion exchange membrane prepared by the preparation method according to claim 1.

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