A method for preparing a super-crosslinked tubular polymer reinforced crosslinked anion exchange membrane for ion transport

Abstract

The application belongs to the technical field of fuel cell materials, and particularly relates to a preparation method of a cross-linked tubular polymer reinforced ion transmission cross-linked anion exchange membrane, which comprises the following steps: (1) preparation of super-cross-linked tubular polymer; (2) preparation of modified polymer; (3) preparation of functionalized modified polymer; and (4) preparation of anion exchange membrane. In the application, the tubular structure and halogen groups in the super-cross-linked tubular polymer are utilized to construct a fast ion channel in the super-cross-linked tubular polymer, so as to enhance the conductivity of the anion exchange membrane. Moreover, the outer surface of the super-cross-linked tubular polymer is uniformly distributed with halogen groups, which can react with the base polymer, so that the base polymer of different chain segments can be linked, and the mechanical properties and mechanical stability of the anion exchange membrane can be enhanced. The strategy has a wide application prospect in the field of anion exchange membrane fuel cells.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell material technology, and specifically relates to a method for preparing a cross-linked anion exchange membrane with enhanced ion transport by a hypercross-linked tubular polymer. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs), as a commercially viable clean energy technology, offer advantages such as room temperature start-up, high energy efficiency, and environmental friendliness, leading to their widespread application in aerospace, transportation, and power supply systems. However, current PEMFCs heavily rely on precious metal catalysts, Nafion membranes, Nafion ionomers, and corrosion-resistant bipolar plates, resulting in high application costs and limiting their widespread adoption. Since 2000, anion exchange membrane fuel cells (HEMFCs) have attracted significant attention due to their alkaline environment. Benefiting from the high pH environment, the oxygen reduction kinetics on the cathode side of HEMFCs are greatly enhanced, making the use of non-precious metal catalysts a promising avenue. Furthermore, a wider variety of alkali-resistant materials are available, enabling the use of inexpensive bipolar plates and significantly reducing costs.

[0003] Although HEMFCs have advantages such as low cost, their lifespan is still much shorter than that of PEMFCs. Among them, HEM (anion exchange membrane) is one of the key components, which determines the lifespan of HEMFCs. During the operation of HEMFCs, back pressure valves are often used to increase the pressure of the gas on both sides (e.g., 0.1 MPa) to improve the battery performance of HEMFCs. Therefore, HEM needs to have excellent mechanical stability. At present, composite or cross-linking methods are one of the effective strategies to improve the mechanical stability of HEM. Composites combine HEM with a high-strength substrate to improve mechanical properties and stability, but they require HEM solubility and substrate compatibility. More importantly, the conductivity and battery performance of the resulting composite membrane are often affected and reduced. For example, Lee et al. prepared a composite of polyarylepiperidine using PE as a substrate, which greatly improved the mechanical properties, but reduced the conductivity and battery performance (YM, Lee, Journal of Materials Chemistry A, 10(12), 6587-6595.). For example, the thioether-crosslinked polybenzimidazole anion exchange membrane synthesized by Chen et al. exhibits improved mechanical properties, but its highest conductivity at 80 °C is only 58 mS / cm (Chen, et al., Reactive and Functional Polymers, 2020, 156:104719.). Therefore, it is necessary to develop a synthetic strategy to improve the mechanical stability of HEMs without sacrificing conductivity. Summary of the Invention

[0004] To address the issues of poor mechanical stability and the need to improve mechanical properties at the expense of conductivity in Hemisphere Matrix Electrochemical Cells (HEMFCs), this invention provides a synthesis strategy that achieves both high conductivity and mechanical stability. One objective of this invention is to utilize halogen groups on the outer wall of a hypercrosslinked tubular polymer tube as a crosslinking agent to improve the mechanical properties and stability of the membrane. Another objective is to utilize the quaternization reaction between halogen groups inside the hypercrosslinked tubular polymer tube and tertiary amines to obtain cationic functional groups, thereby ensuring good conductivity.

[0005] To achieve the above objectives, the following technical solution is adopted:

[0006] A method for preparing a cross-linked anion exchange membrane with enhanced ion transport by a hypercross-linked tubular polymer includes the following steps:

[0007] (1) Preparation of modified polymers:

[0008] Prepare a clean round-bottom flask, weigh out a certain amount of base polymer B, then add an appropriate amount of good solvent to dissolve the base polymer, obtaining a 5-20 wt% base polymer solution. Next, weigh out and add the hypercrosslinked tubular polymer A according to the mass ratio, and ultrasonically disperse at room temperature for 3-24 hours. Then, raise the system temperature to 80-120℃ and maintain the reaction temperature for 24 hours. After the reaction is complete, collect the reaction solution to obtain the modified polymer solution for later use.

[0009] (2) Preparation of functionalized modified polymers:

[0010] Prepare a clean round-bottom flask, add the reaction solution obtained in step (3), and then introduce trimethylamine into the system by bubbling trimethylamine aqueous solution with nitrogen gas, controlling the system temperature at 20-80℃ and keeping it at that temperature for 24-48h. After the reaction is complete, add a certain proportion of haloalkanes functionalizing reagent C to the system and keep the system temperature at 30-100℃ for 24-48h. After the reaction is complete, collect the reaction solution to obtain the functionalized modified polymer solution for later use. Through the functionalization of trimethylamine and iodomethane, the halogens in the hypercrosslinked tubular polymer and the tertiary amines in the base polymer are completely converted into quaternary ammonium groups;

[0011] (3) Preparation of anion exchange membranes:

[0012] Prepare a clean glass mold, take a certain amount of modified anionic polyelectrolyte solution, dilute it with a good solvent, and then dry it at 60-120℃ by casting to obtain the target anion exchange membrane.

[0013] Based on the above technical solutions, preferably, the hypercrosslinked tubular polymer described in step (1) is obtained by polymerization of any one of the following aromatic halide monomers:

[0014]

[0015] Based on the above technical solutions, preferably, the substrate polymer in step (1) is any one of the following, or any at least two of the following:

[0016]

[0017] The F group in the base polymer can be any of the following:

[0018]

[0019] Based on the above technical solutions, preferably, the base polymer can be prepared as a copolymer of terphenyl and N-methylpiperidone according to the literature (Y. Yanet, al., Nature Energy 2019, 4, 392-398.).

[0020] Based on the above technical solutions, the preferred method for preparing the hypercrosslinked tubular polymer in step (1) is as follows: Prepare a clean round-bottom flask, measure a certain amount of polydimethylsiloxane and add it to the flask, then add a certain proportion of 1,2-dichloroethane solution of aromatic halides and 1,2-dichloroethane solution of anhydrous ferric chloride, and stir vigorously at room temperature for 10-100 min. Then raise the reaction temperature of the system to 80-100℃ and reflux for 12-48 h. After the reaction is completed, collect the product by vacuum filtration and purify it with ethanol using a Soxhlet extractor. The hypercrosslinked tubular polymer can be obtained by vacuum drying at 60℃.

[0021] Based on the above technical solutions, preferably, the ratio of the aromatic halogenated compound to polydimethylsiloxane is 1g:(50-100)ml, and more preferably 1g:100ml.

[0022] Based on the above technical solutions, preferably, the molar ratio of the aromatic halogenated compound to 1,2-dichloroethane is 1:(10-100), more preferably 1:10; the molar ratio of anhydrous ferric chloride to 1,2-dichloroethane is 1:(10-100), more preferably 1:(10-20), and even more preferably 1:17.8.

[0023] Based on the above technical solution, preferably, the mass ratio of the aromatic halide to ferric chloride is (0.3-3.0):1, and more preferably (0.5-2.5):1.

[0024] Based on the above technical solutions, preferably, the molar ratio of the base polymer to the super-crosslinked tubular polymer in step (1) is 1:(0.001-0.5), more preferably 1:(0.001-0.01), and more preferably 1:0.005.

[0025] Based on the above technical solutions, preferably, the halogenated hydrocarbon mentioned in step (2) can be iodomethane, bromomethane, benzyl chloride, allyl chloride, iodoethane, bromoethane, etc.

[0026] Based on the above technical solutions, preferably, the trimethylamine in step (2) is in excess relative to the modified polymer.

[0027] Based on the above technical solutions, preferably, the molar ratio of the base polymer to iodomethane in step (2) is 1:(1-10), more preferably 1:(1-10), and even more preferably 1:5.

[0028] Based on the above technical solutions, preferably, the good solvent mentioned in steps (1) and (3) is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0029] Based on the above technical solution, preferably, the concentration of the trimethylamine aqueous solution in step (2) is 25-50 wt%, preferably 30 wt%.

[0030] The cross-linked anion exchange membrane with enhanced ion transport by the super-crosslinked tubular polymer obtained by the above preparation method includes a functionally modified polymer. This polymer is obtained by cross-linking super-crosslinked tubular polymer A and base polymer B through a quaternization reaction, followed by trimethylamine functionalization of the super-crosslinked tubular polymer A, and finally quaternization of the base polymer with a haloalkane functionalizing agent C. The structure is as follows:

[0031]

[0032] Beneficial effects

[0033] This invention provides a cross-linked anion exchange membrane with enhanced ion transport via a hypercrosslinked tubular polymer. By bonding and functionalizing a base polymer with a hypercrosslinked tubular polymer, the conductivity and mechanical properties are enhanced. The presence of halogen groups on the exterior of the hypercrosslinked tubular polymer provides reaction sites for the cross-linking of the base polymer, thereby improving mechanical properties. Furthermore, the halogen groups within the hypercrosslinked tubular polymer and the tertiary amine groups of the base polymer can be further quaternized to generate cationic groups, thus evolving into fast ion transport channels and interconnected ion channels, further improving conductivity. While maintaining good conductivity, the cross-linking of the hypercrosslinked tubular polymer with the base polymer improves the mechanical properties and mechanical stability of the anion exchange membrane. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the spatial structure.

[0035] Figure 2This is an SEM image of the hypercrosslinked tubular polymer from step (2) of Example 2.

[0036] Figure 3 This is the conductivity diagram of Example 2.

[0037] Figure 4 This is a mechanical performance diagram of Example 2. Detailed Implementation

[0038] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0039] Example 1

[0040] A method for preparing a cross-linked anion exchange membrane with enhanced ion transport by a hypercross-linked tubular polymer is as follows:

[0041] (1) Preparation of the base polymer

[0042] A copolymer of p-terphenyl and N-methylpiperidone was prepared according to the literature (Y. Yan et al., Nature Energy 2019, 4, 392-398.).

[0043] (2) Preparation of hypercrosslinked tubular polymers:

[0044] 100 ml of polydimethylsiloxane was added to a round-bottom flask. Then, 0.8 g of 1,4-dibenzyl chloride and 0.45 g of anhydrous ferric chloride were dispersed in two 8 ml portions of 1,2-dichloroethane, respectively, to obtain 1,4-dibenzyl chloride and anhydrous ferric chloride solutions in 1,2-dichloroethane. The 1,4-dibenzyl chloride and anhydrous ferric chloride solutions in 1,2-dichloroethane were slowly added dropwise to the polydimethylsiloxane system, and the mixture was stirred vigorously for 60 min. The reaction temperature was then increased to 80 °C and refluxed for 24 h. After the reaction was complete, the product was collected by vacuum filtration and purified with ethanol. The hypercrosslinked tubular polymer was obtained by vacuum drying at 60 °C.

[0045] (3) Preparation of modified polymers:

[0046] 1 g of the base polymer was dispersed in 10 ml of DMSO, and 0.001 g of the hypercrosslinked tubular polymer was added. The mixture was ultrasonically dispersed for 5 h. The reaction was then carried out at 90 °C for 24 h. After the reaction was complete, the modified anionic polymer solution was obtained and collected for later use.

[0047] (4) Preparation of functionalized modified polymers:

[0048] Prepare a clean round-bottom flask, add the reaction solution obtained in step (3), and then introduce excess trimethylamine into the system by bubbling 300 ml of 30 wt% trimethylamine aqueous solution with nitrogen gas (at a rate of one bubble per second). Control the system temperature at 40°C and maintain the temperature for 24 h. After the reaction is complete, add 2 ml of iodomethane to the system and maintain the system temperature at 80°C for 24 h. After the reaction is complete, collect the reaction solution for later use.

[0049] (5) Preparation of anion exchange membranes:

[0050] Take 3 ml of the reaction solution obtained in step (3), add 7 ml of DMSO to dilute, and then dry at 80 °C by casting to obtain the target anion exchange membrane.

[0051] Example 2

[0052] A method for preparing a cross-linked anion exchange membrane with enhanced ion transport by a hypercross-linked tubular polymer is as follows:

[0053] (1) Preparation of the base polymer

[0054] A copolymer of p-terphenyl and N-methylpiperidone was prepared according to the literature (Y. Yan et al., Nature Energy 2019, 4, 392-398.).

[0055] (2) Preparation of hypercrosslinked tubular polymers:

[0056] 100 ml of polydimethylsiloxane was added to a round-bottom flask. Then, 0.8 g of 1,4-dibenzyl chloride and 0.45 g of anhydrous ferric chloride were dispersed in two 8 ml portions of 1,2-dichloroethane, respectively, to obtain 1,4-dibenzyl chloride and anhydrous ferric chloride solutions in 1,2-dichloroethane. The 1,4-dibenzyl chloride and anhydrous ferric chloride solutions in 1,2-dichloroethane were slowly added dropwise to the polydimethylsiloxane system, and the mixture was stirred vigorously for 60 min. The reaction temperature was then increased to 80 °C and refluxed for 24 h. After the reaction was complete, the product was collected by vacuum filtration and purified with ethanol. The hypercrosslinked tubular polymer was obtained by vacuum drying at 60 °C.

[0057] (3) Preparation of modified polymers:

[0058] 1 g of the base polymer was dispersed in 10 ml of DMSO, and 0.005 g of the hypercrosslinked tubular polymer was added. The mixture was ultrasonically dispersed for 5 h. The reaction was then carried out at 90 °C for 24 h. After the reaction was complete, the modified anionic polymer solution was obtained and collected for later use.

[0059] (4) Preparation of functionalized modified polymers:

[0060] Prepare a clean round-bottom flask, add the reaction solution obtained in step (3), and then introduce excess trimethylamine into the system by bubbling 300 ml of 30 wt% trimethylamine aqueous solution with nitrogen gas (at a rate of one bubble per second). Control the system temperature at 40°C and maintain the temperature for 24 h. After the reaction is complete, add 2 ml of iodomethane to the system and maintain the system temperature at 80°C for 24 h. After the reaction is complete, collect the reaction solution for later use.

[0061] (5) Preparation of anion exchange membranes:

[0062] Take 3 ml of the reaction solution obtained in step (3), add 7 ml of DMSO to dilute, and then dry at 80 °C by casting to obtain the target anion exchange membrane.

[0063] like Figure 2 The SEM images shown show that the hypercrosslinked tubular polymer prepared in step (2) exhibits a nanotube morphology with a diameter of 200-400 nm and a length of more than 5 μm.

[0064] like Figure 3 The conductivity diagram shown demonstrates that the cross-linked anion exchange membrane prepared in Example 2 exhibits excellent conductivity, with its bicarbonate ion form achieving a conductivity of 95 mS / cm at 90°C.

[0065] like Figure 4 The tensile properties diagram shown demonstrates that the cross-linked ion exchange membrane prepared in Example 2 exhibits excellent mechanical strength, with the bicarbonate ion membrane achieving a tensile strength of 55 MPa and an elongation at break of 18% at room temperature.

[0066] Example 3

[0067] A method for preparing a cross-linked anion exchange membrane with enhanced ion transport by a hypercross-linked tubular polymer is as follows:

[0068] (1) Preparation of the base polymer

[0069] A copolymer of p-terphenyl and N-methylpiperidone was prepared according to the literature (Y. Yan et al., Nature Energy 2019, 4, 392-398.).

[0070] (2) Preparation of hypercrosslinked tubular polymers:

[0071] 100 ml of polydimethylsiloxane was added to a round-bottom flask. Then, 0.8 g of 1,4-dibenzyl chloride and 0.45 g of anhydrous ferric chloride were dispersed in two 8 ml portions of 1,2-dichloroethane, respectively, to obtain 1,4-dibenzyl chloride and anhydrous ferric chloride solutions in 1,2-dichloroethane. The 1,4-dibenzyl chloride and anhydrous ferric chloride solutions in 1,2-dichloroethane were slowly added dropwise to the polydimethylsiloxane system, and the mixture was stirred vigorously for 60 min. The reaction temperature was then increased to 80 °C and refluxed for 24 h. After the reaction was complete, the product was collected by vacuum filtration and purified with ethanol. The hypercrosslinked tubular polymer was obtained by vacuum drying at 60 °C.

[0072] (3) Preparation of modified polymers:

[0073] 1 g of the base polymer was dispersed in 10 ml of DMSO, and 0.01 g of the hypercrosslinked tubular polymer was added. The mixture was ultrasonically dispersed for 5 h. The reaction was then carried out at 90 °C for 24 h. After the reaction was complete, the modified anionic polymer solution was obtained and collected for later use.

[0074] (4) Preparation of functionalized modified polymers:

[0075] Prepare a clean round-bottom flask, add the reaction solution obtained in step (3), and then introduce excess trimethylamine into the system by bubbling 300 ml of 30 wt% trimethylamine aqueous solution with nitrogen gas (at a rate of one bubble per second). Control the system temperature at 40°C and maintain the temperature for 24 h. After the reaction is complete, add 2 ml of iodomethane to the system and maintain the system temperature at 80°C for 24 h. After the reaction is complete, collect the reaction solution for later use.

[0076] (5) Preparation of anion exchange membranes:

[0077] Take 3 ml of the reaction solution obtained in step (3), add 7 ml of DMSO to dilute, and then dry at 80 °C by casting to obtain the target anion exchange membrane.

Claims

1. A method for preparing a cross-linked anion exchange membrane, characterized in that, Includes the following steps: (1) Preparation of modified polymers: The base polymer was dissolved in a good solvent, and the supercrosslinked tubular polymer was added. The mixture was ultrasonically dispersed for 3-24 h, and then reacted at 80-120℃ for 12-48 h to obtain a modified polymer solution. (2) Preparation of functionalized modified polymers: Trimethylamine was introduced into the modified polymer solution by bubbling an aqueous solution of trimethylamine with nitrogen gas and maintaining the temperature at 20-80 °C for 24-48 h. Then, a halogenated hydrocarbon was added to the system and the temperature was maintained at 30-100 °C for 24-48 h to obtain the functionalized modified polymer solution. (3) Preparation of anion exchange membranes: The functionalized modified polymer solution was diluted with a good solvent, and then the target anion exchange membrane was prepared by casting at 60-120℃. The hypercrosslinked tubular polymer is obtained by polymerization of any one of the following aromatic halide monomers: The base polymer is any one of the following, or any at least two of the following: The F group in the base polymer is any one of the following: 。 2. The preparation method according to claim 1, characterized in that, The method for preparing the hypercrosslinked tubular polymer is as follows: add a 1,2-dichloroethane solution of aromatic halides and a 1,2-dichloroethane solution of anhydrous ferric chloride to polydimethylsiloxane, stir for 10-100 min, then raise the reaction temperature of the system to 80-100 ℃, reflux for 12-48 h, after the reaction is completed, collect the product by vacuum filtration, purify it with ethanol, and dry it to obtain the hypercrosslinked tubular polymer.

3. The preparation method according to claim 2, characterized in that, The ratio of the aromatic halide to polydimethylsiloxane is 1g:(50-100)ml, and the mass ratio of the aromatic halide to ferric chloride is 0.3-3.0:

1.

4. The preparation method according to claim 2, characterized in that, In the 1,2-dichloroethane solution of the aromatic halide, the molar ratio of the aromatic halide to 1,2-dichloroethane is 1:10-100; in the 1,2-dichloroethane solution of anhydrous ferric chloride, the molar ratio of anhydrous ferric chloride to 1,2-dichloroethane is 1:10-100.

5. The preparation method according to claim 1, characterized in that, The molar ratio of the base polymer to the hypercrosslinked tubular polymer in step (2) is 1:0.001-0.

5.

6. The preparation method according to claim 1, characterized in that, The haloalkane mentioned in step (2) is one or more of iodomethane, bromomethane, benzyl chloride, allyl chloride, iodoethane, and bromoethane.

7. The preparation method according to claim 1, characterized in that, The concentration of the trimethylamine aqueous solution in step (2) is 25-50 wt%, the trimethylamine is in excess relative to the modified polymer, and the molar ratio of the base polymer to the haloalkanes is 1:1-10.

8. The preparation method according to claim 2, characterized in that, The good solvent mentioned in steps (1) and (3) is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

9. The cross-linked anion exchange membrane obtained by the preparation method according to any one of claims 1-8.

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