阅读说明：本技术 一种基于柔性长侧链多阳离子结构的交联型碱性阴离子膜的制备方法 (Preparation method of crosslinking type alkaline anionic membrane based on flexible long-side-chain multi-cation structure ) 是由 张凤祥 贾亚斌 于 2019-11-07 设计创作，主要内容包括：本发明提供一种基于柔性长侧链多阳离子结构的交联型碱性阴离子膜的制备方法,属于燃料电池阴离子交换膜材料领域。该碱性阴离子交换膜由卤代多阳离子交联剂与联苯类聚合物通过门秀金反应制备而成,包括聚合物主链进行合成、聚合物膜主链进行离子化、铸膜和碱处理四步。本发明方法简单,多阳离子结构促进了亲水疏水微相分离结构的形成,柔性长侧链交联结构抑制膜的吸水溶胀,在保证电导率的基础上改善膜的机械性能,从而缓解电导率与机械强度之间的矛盾,且能够提升离子交换膜的碱稳。(The invention provides a preparation method of a cross-linking type alkaline anion membrane based on a flexible long side chain multi-cation structure, belonging to the field of fuel cell anion exchange membrane materials. The alkaline anion-exchange membrane is prepared by reacting a halogenated polycation cross-linking agent with a biphenyl polymer through a Moxiujin reaction, and comprises four steps of polymer main chain synthesis, polymer membrane main chain ionization, membrane casting and alkali treatment. The method is simple, the formation of a hydrophilic and hydrophobic micro-phase separation structure is promoted by a multi-cation structure, the water absorption swelling of the membrane is inhibited by the flexible long-side chain crosslinking structure, the mechanical performance of the membrane is improved on the basis of ensuring the conductivity, so that the contradiction between the conductivity and the mechanical strength is relieved, and the alkali stability of the ion exchange membrane can be improved.)

1. A preparation method of a cross-linking type basic anionic membrane based on a flexible long side chain polycation structure is characterized by comprising the following steps:

(1) copolymerization synthesis of copolymerized biphenyl class oxygen-free main chain

Dissolving biphenyl substances in a solvent A, and adding a mixed reagent under the protection of nitrogen atmosphere; then adding trifluoroacetic acid and trifluoromethanesulfonic acid as catalysts, and reacting for 2-5 h under ice bath; the reaction mixture was poured into a precipitant to precipitate, and dried in vacuo to give a polymer: a copolymerized biphenyl oxygen-free backbone; the molar ratio of the biphenyl substances, the solvent A and the catalyst is 1: 200-240: 9-10; the mixed reagent consists of N-methyl piperidone and 1,1, 1-trifluoroacetone or 1,1, 1-trifluoroacetophenone, wherein the molar ratio of the N-methyl piperidone to the 1,1, 1-trifluoroacetone or 1,1, 1-trifluoroacetophenone is 1: 0 to 1; the degree of polymer functionalization is controlled by controlling the addition amount of 1,1, 1-trifluoroacetone or 1,1, 1-trifluoroacetophenone;

(2) preparation of ionizing Agents

Firstly, adding butanediamine or pentanediamine into ethanol serving as a solvent, and preparing a co-solution with the volume fraction of 2-6%; secondly, dropwise adding 1, 4-dibromobutane or 1, 5-dibromopentane into the co-solution, stirring the obtained solution at 0-4 ℃ for 8-12 hours, and keeping the solution at 50 ℃ for 3-8 hours; thirdly, pouring the reacted solution into a precipitator, cooling to 0-4 ℃, standing in a refrigerator and precipitating a product; finally, collecting the crude product through vacuum absorption, washing the crude product with a precipitator to remove unreacted monomers, and drying the crude product in vacuum to obtain a crosslinking reagent for an ionization reaction;

(3) ionizing the main chain of the polymer film, dissolving the copolymerized biphenyl oxygen-free main chain obtained in the step (1) in an organic solvent, adding the ionizing reagent obtained in the step (2) as a cross-linking agent, and performing an ionizing reaction for 3-24 hours at 40-80 ℃; the molar ratio of the polymer to the organic solvent to the ionizing agent is 1: 10: 1.5-2;

(4) cast film

Placing the reaction mixture prepared in the step (3) on a glass plate to form a film by casting or tape casting;

(5) alkali treatment to obtain anion exchange membrane

And stripping the obtained anion exchange membrane from the surface of the glass plate, soaking in 1.0M alkali solution for 24 hours, and washing off free ions on the surface of the membrane to obtain the anion exchange membrane.

2. The method for preparing the cross-linked basic anionic membrane based on the flexible long-side chain polycation structure according to claim 1, wherein the molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid in the catalyst in step (1) is 1: 6-8.

3. The method for preparing the cross-linked basic anionic membrane based on the flexible long-side chain polycation structure according to claim 1, wherein the biphenyl substances in the step (1) comprise biphenyl and m-terphenyl.

4. The method for preparing the cross-linked basic anionic membrane based on the flexible long-side chain polycation structure according to claim 1, wherein the solvent A in the step (1) can be dichloromethane.

5. The method for preparing the cross-linking type basic anionic membrane based on the flexible long-side chain polycation structure according to claim 1, wherein the temperature of the vacuum drying in the step (1) is 40-100 ℃, and the time is 12-48 hours.

6. The method for preparing the cross-linking type basic anionic membrane based on the flexible long-side chain polycation structure according to claim 1, wherein in the step (2), 22mL of dibromo-class substance is added for every 2mL of diamine-type substance.

7. The method for preparing the cross-linking type basic anionic membrane based on the flexible long-side chain polycation structure according to claim 1, wherein the temperature of the vacuum drying in the step (2) is 30 ℃ and the time is 12 hours.

8. The method for preparing the cross-linking type basic anionic membrane based on the flexible long-side chain polycation structure according to claim 1, wherein the precipitating agent in the step (2) and the step (1) comprises petroleum ether and ethyl acetate.

Technical Field

The invention belongs to the field of fuel cell anion exchange membrane materials, and relates to a preparation method of a cross-linking type alkaline anion membrane based on a flexible long side chain multi-cation structure.

Background

At present, energy shortage and environmental pollution have become the two most important problems facing the present society, and fuel cells are receiving wide attention from all countries as a new clean energy source. Alkaline polymer fuel cells have been rapidly developed by virtue of their fast reaction kinetics, the ability to use non-noble metal catalysts, no carbonate crystallization, low fuel permeation rates, and the like.

However, the commercialization of alkaline polymer fuel cells is still faced with many challenges, and the alkaline anion-exchange membrane as a key material has two major problems of low conductivity and poor chemical stability in alkaline environment. Therefore, how to improve the chemical stability and conductivity of the anionic membrane becomes a problem to be solved urgently.

As a traditional ion exchange group, the SN generated by quaternary ammonium salt under the condition of high temperature and alkali₂In recent years, electrolyte membranes containing novel ionic groups such as imidazole, morpholine, guanidino, pyrrolidine and the like have attracted interest.

In contrast, in recent years, Kreuer et al found that 6-membered aliphatic heterocyclyl cationic piperidines exhibit high resistance to nucleophilic substitution and elimination under basic conditions and high temperatures. The authors attribute this to a high transition state energy and low ring strain of the piperidine structure in the degradation reaction, and thus are more stable in alkaline environments.

Disclosure of Invention

Aiming at the two problems of the anion membrane, the invention provides a novel anion exchange membrane for an alkaline fuel cell and a preparation method thereof, wherein a piperidine ring and quaternary ammonium salt cations with excellent alkali stability are used as ionizing reagents, a polymer without heteroatoms in a framework is used as an ion exchange membrane main chain, and an ion exchange membrane with a multi-cation structure is prepared.

In order to achieve the purpose, the invention adopts the technical scheme that:

a preparation method of a cross-linking type basic anion membrane based on a flexible long side chain polycation structure comprises the steps of firstly reacting an anaerobic structure containing biphenyl and the like with N-methyl piperidone and 1,1, 1-trifluoroacetone to obtain a first-step product, then reacting with excessive large-volume halide to obtain an ionized polymer, and preparing the anion exchange membrane by a casting method. The preparation process comprises the steps of synthesizing a polymer main chain, ionizing the polymer film main chain, casting a film and treating alkali. The method comprises the following specific steps:

(1) copolymerization synthesis of copolymerized biphenyl class oxygen-free main chain

Dissolving biphenyl substances into a solvent A, and adding a mixed reagent under the protection of nitrogen atmosphere. And then adding trifluoroacetic acid and trifluoromethanesulfonic acid as catalysts, and reacting for 2-5 h under ice bath. The reaction mixture was poured into a precipitant to precipitate, and dried in vacuo to give a polymer: copolymerized biphenyls oxygen-free backbones. The molar ratio of the biphenyl substances, the solvent A and the catalyst is 1: 200-240: 9 to 10. The mixed reagent consists of N-methyl piperidone and 1,1, 1-trifluoroacetone or 1,1, 1-trifluoroacetophenone, wherein the molar ratio of the N-methyl piperidone to the 1,1, 1-trifluoroacetone or 1,1, 1-trifluoroacetophenone is 1: 0 to 1; the degree of functionalization of the polymer is controlled by controlling the addition amount of 1,1, 1-trifluoroacetone or 1,1, 1-trifluoroacetophenone, and the degree of substitution of the polymer is in the range of 0.3-1 mmol-g^-1。

The molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid in the catalyst of step (1) is 1: 6-8.

The biphenyl substances in the step (1) comprise biphenyl and m-terphenyl.

The solvent A in the step (1) can be dichloromethane. The precipitant is ethyl acetate and petroleum ether.

The temperature of the vacuum drying in the step (1) is 40-100 ℃, and the time is 12-48 hours;

(2) preparation of ionizing Agents

Firstly, adding diamine substances into solvent ethanol, and preparing a co-solution with the volume fraction of 2-6%. Secondly, adding a dibromo substance into the co-solution dropwise, stirring the obtained solution at 0-4 ℃ for 8-12 hours, and keeping the solution at 50 ℃ for 3-8 hours, wherein 22mL of the dibromo substance is added to every 2mL of diamine substance. And thirdly, pouring the reacted solution into a precipitator, cooling to 0-4 ℃, and placing in a refrigerator for 12 hours to precipitate the product. Finally, the crude product was collected by vacuum absorption and washed with a precipitant to remove unreacted monomers, and after vacuum drying at 30 ℃ for 12 hours, a crosslinking agent for ionization reaction was obtained. The diamine substance in the step (2) comprises butanediamine and pentanediamine.

The dibromo-class substance in the step (2) comprises 1, 4-dibromobutane and 1, 5-dibromopentane.

The precipitant in the step (2) comprises petroleum ether and ethyl acetate.

(3) And (2) ionizing the main chain of the polymer film, dissolving the copolymerized biphenyl oxygen-free main chain obtained in the step (1) in an organic solvent, adding an ionizing reagent obtained in the step (2) as a cross-linking agent, and performing an ionizing reaction for 3-24 hours at the temperature of 40-80 ℃. The molar ratio of the polymer to the organic solvent to the ionizing agent is 1: 10: 1.5 to 2.

The organic solvent in the step (3) can be N, N-dimethylformamide and N-methylpyrrolidone.

(4) Cast film

And (4) placing the reaction mixture prepared in the step (3) on a glass plate to be cast into a film or cast into a film, and standing for 12-36 hours at the temperature of 60-80 ℃.

(5) Alkali treatment to obtain anion exchange membrane

And stripping the obtained anion exchange membrane from the surface of the glass plate, soaking in 1.0M alkali solution for 24 hours, and washing off free ions on the surface of the membrane to obtain the anion exchange membrane.

The cross-linking type alkaline anion-exchange membrane based on the flexible long-side-chain polycation structure is applied to the field of fuel cells, and is prepared by reacting a halogenated polycation cross-linking agent with a biphenyl polymer through a Moxiujin reaction.

The biphenyl polymer is a biphenyl anaerobic main chain and a m-terphenyl anaerobic main chain, and the substitution degree range of the polymer is 0.3-1 mmol/g^-1. It is composed ofThe structural formula is as follows:

the invention has the beneficial effects that:

(1) the piperidine structure enhances the alkali resistance of the anionic membrane due to the high transition state energy and low ring strain of its degradation reaction; the oxygen-free main chain does not contain electron-withdrawing groups such as ether bond and the like, so that OH is reduced^-The attack of the ion exchange membrane improves the alkali stability of the ion exchange membrane;

(2) the formation of a hydrophilic and hydrophobic micro-phase separation structure is promoted by the multi-cation structure, the flexible long-side chain crosslinking structure inhibits the water absorption swelling of the membrane, the anion exchange membrane with high substitution degree is prepared, the mechanical property of the membrane is improved on the basis of ensuring the conductivity, and thus the contradiction between the conductivity and the mechanical strength is relieved.

Drawings

FIG. 1 shows FT-IR spectrum and chemical structure of the ion exchange membrane after ionization in example 1. In the spectrogram: the abscissa is the wavenumber and the ordinate is the intensity.

FIG. 2 is a graph of H for the first step product copolymerization of oxygen free backbone polymers¹NMR spectrum with chemical shift value ppm on the abscissa.

FIG. 3 shows H of an ionic liquid¹NMR spectrum with chemical shift value ppm on the abscissa.

Detailed Description

The method for producing a crosslinked anionic membrane according to the present invention will be described in further detail below with reference to examples.