阅读说明：本技术 一种含密集离子串嵌段型阴离子交换膜及其制备方法 (Block type anion exchange membrane containing dense ion string and preparation method thereof ) 是由 赖傲楠 王贞 郑经纬 周树锋 于 2020-07-31 设计创作，主要内容包括：本发明提供了一种含密集离子串嵌段型阴离子交换膜及其制备方法,可用于碱性燃料电池。该阴离子交换膜的结构特点是在嵌段共聚物的亲水段上密集地接枝了多个离子串作为功能基团。其制备过程主要包括：(1)含四苯甲基的亲水段以及含悬挂腈基的疏水段的制备；(2)嵌段共聚物的制备与溴化改性；(3)含密集离子串嵌段型阴离子交换膜的制备。本发明制备的阴离子交换膜具有发达的离子传输通道,具备高含水率以及低溶胀率特性,克服了现有阴离子交换膜高含水率、高电导率与低溶胀率不可兼得的缺点。且制备过程不使用剧毒致癌的氯甲醚试剂,在碱性燃料电池领域具有广阔的应用前景。(The invention provides a block type anion exchange membrane containing a dense ion string and a preparation method thereof, which can be used for an alkaline fuel cell. The anion exchange membrane has the structural characteristic that a plurality of ion strings are densely grafted on a hydrophilic section of a block copolymer as functional groups. The preparation process mainly comprises the following steps: (1) preparing a hydrophilic section containing tetraphenylmethyl and a hydrophobic section containing a pendant nitrile group; (2) preparing a block copolymer and modifying by bromination; (3) preparing the block type anion exchange membrane containing the dense ion string. The anion exchange membrane prepared by the invention has a developed ion transmission channel, has the characteristics of high water content and low swelling rate, and overcomes the defect that the existing anion exchange membrane cannot achieve the characteristics of high water content, high conductivity and low swelling rate. And the preparation process does not use highly toxic carcinogenic chloromethyl ether reagent, and has wide application prospect in the field of alkaline fuel cells.)

1. An anion exchange membrane containing dense ion string block type is characterized in that: the molecular structural formula is as follows:

wherein m is an integer of 5 to 50, n is an integer of 5 to 50, and at least one R is

P₁at least one selected from (a1) to (e 1); p₂At least one selected from (a1) to (e 1);

ar is selected from at least one of (a2) - (e 2);

2. the preparation method of the anion exchange membrane containing the dense ion string block type as claimed in claim 1, which is characterized in that: the method comprises the following steps:

1) synthesis of hydrophilic chain segment oligomer: will have P₁The tetramethyl bisphenol monomer with the structure and the dihalogen monomer with the Ar structure are fed in a molar ratio of m (m-1) under the protection of nitrogen and are equivalent to the monomer with P₁Anhydrous potassium carbonate with 1.5-5 times of molar weight of structural tetramethyl bisphenol monomer and toluene are dissolved in a polar aprotic solvent, the mixture is reacted for 4-6 hours at 130-150 ℃, then the temperature is raised to 160-170 ℃ for reaction for 10-12 hours, and then 0.04-0.06 m mol of P is added₁A tetramethyl bisphenol monomer with a structure of 160-1Continuously reacting for 1-2 h at 70 ℃, cooling, precipitating with an alcohol-water solution, filtering, washing and drying to obtain a hydrophilic chain segment oligomer;

2) synthesis of hydrophobic segment oligomer: will have P₂Bisphenol monomer and 3, 5-dichlorobenzonitrile monomer of the structure are fed in a molar ratio of n (n +1), protected by nitrogen and equivalent to P₂Dissolving a bisphenol monomer with a structure in a polar aprotic solvent in the presence of anhydrous potassium carbonate and toluene, wherein the anhydrous potassium carbonate is 1.5-5 times the mol of the bisphenol monomer, reacting at 130-145 ℃ for 3-5 hours, heating to 150-160 ℃ for reacting for 8-10 hours, adding 0.04-0.06 n mol of 3, 5-dichlorobenzonitrile monomer, continuing to react at 150-160 ℃ for 0.4-0.6 hour, cooling, precipitating with an alcohol-water solution, filtering, washing, and drying to obtain a hydrophobic chain segment oligomer;

3) synthesis of Block copolymer: feeding the prepared hydrophilic chain segment oligomer and hydrophobic chain segment oligomer in an equimolar ratio, dissolving the hydrophilic chain segment oligomer and the hydrophobic chain segment oligomer in a polar aprotic solvent under the protection of nitrogen and in the presence of anhydrous potassium carbonate and toluene which are 1-100 times the moles of the hydrophilic chain segment oligomer, reacting for 5-6 h at 140-150 ℃, heating to 160-180 ℃ for reacting for 20-24 h, cooling, precipitating with an alcohol-water solution, filtering, washing and drying to obtain a block copolymer;

4) synthesis of bromomethylated Block copolymer: dissolving the block copolymer obtained in the step 3) in 1,1,2, 2-tetrachloroethane, then adding N-bromosuccinimide and an initiator, reacting for 3-8 h at 84-86 ℃, cooling, precipitating with methanol, filtering, washing, and drying to obtain a bromomethylation block copolymer;

5) preparation of anion exchange membrane: dissolving the bromomethylation segmented copolymer obtained in the step 4) in DMSO, adding a quaternizing agent with an R structure, dissolving and reacting at 30-60 ℃ for 18-48 h to obtain a casting solution; and finally coating the membrane casting solution on a substrate, heating to volatilize a solvent to obtain a solid membrane, immersing the solid membrane into alkali liquor, reacting for 24-48 h, and fully washing with water to obtain the anion exchange membrane containing the dense ion string block type.

3. The compact ion cluster block-containing anion of claim 2The preparation method of the proton exchange membrane is characterized by comprising the following steps: said has P₁The tetramethylbisphenol monomer of structure includes at least one of 4,4 '-methylenebis (2, 6-dimethyl) phenol, 2-bis (4-hydroxy-3, 5-dimethylphenyl) propane, α' -bis (4-hydroxy-3, 5-dimethylphenyl) -1, 4-diisopropylbenzene, 3 '-bis (4-hydroxy-3, 5-dimethylphenyl) -phenolphthalein, 3-bis (4-hydroxy-3, 5-dimethylphenyl) phthalein, or 9,9' -bis (4-hydroxy-3, 5-dimethylphenyl) fluorene.

4. The method of preparing an anion exchange membrane comprising compact ion-exchanger blocks of claim 2, wherein: the dihalo monomer with the Ar structure comprises at least one of 4,4 '-dichlorodiphenyl sulfone, 4' -dichlorobenzophenone, 4 '-dichlorodiphenylmethane, 4' -dichlorobiphenyl or 3, 5-dichlorobenzonitrile.

5. The method of preparing an anion exchange membrane comprising compact ion-exchanger blocks of claim 2, wherein: the polar aprotic solvent includes at least one of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, or dimethylsulfoxide.

6. The method of preparing an anion exchange membrane comprising compact ion-exchanger blocks of claim 2, wherein: in the step 4), the molar ratio of the block copolymer, the N-bromosuccinimide and the initiator is 1 (10-100) to 0.5-5.

7. The method of preparing an anion exchange membrane comprising compact ion-exchanger blocks of claim 2, wherein: the initiator comprises at least one of azobisisobutyronitrile or benzoyl peroxide.

8. The method of preparing an anion exchange membrane comprising compact ion-exchanger blocks of claim 2, wherein: the quaternizing agent comprises at least one of 6- (dimethylamino) -N, N, N-trimethylhexane-1-ammonium bromide, 6- (dimethylamino) -N-ethyl-N, N-dimethylhexane-1-ammonium bromide, or 1- (N ', N' -dimethylamino) -6,12- (N, N, N-trimethylammonium) dodecylammonium bromide.

9. The method for preparing an anion exchange membrane comprising compact ion-cluster blocks according to claim 2, wherein: in the step 5), the molar ratio of benzyl bromide groups in the bromomethylation segmented copolymer to the quaternizing agent is 1 (1-6).

10. The method of preparing an anion exchange membrane comprising compact ion-exchanger blocks of claim 2, wherein: step 5), the alkali liquor comprises at least one of potassium hydroxide solution or sodium hydroxide solution; the aqueous alcohol solution comprises an aqueous methanol solution; the substrate comprises a polytetrafluoroethylene sheet or a glass sheet.

Technical Field

The invention belongs to the field of alkaline fuel cells, and particularly relates to an anion exchange membrane and a synthesis method thereof.

Background

A Fuel Cell (Fuel Cell) is a power generation device that directly and efficiently converts chemical energy stored in Fuel and oxidant into electrical energy by using a chemical reaction technology, has the advantages of high efficiency, high energy density, environmental friendliness, portability and the like, and is considered as a fourth generation power generation technology. At present, alkaline Anion Exchange Membrane Fuel Cells (AEMFCs) using Anion Exchange Membranes (AEMs) as polyelectrolytes are receiving attention because they have the characteristics of high electrode reaction activity, capability of using non-noble metal electrode catalysts, low corrosiveness and the like, and have become a research hotspot in the field of current fuel cells, and from the viewpoint of energy conservation and environmental protection, fuel cells are the most promising power generation technology. Wherein, the anion exchange membrane is a key component of AEMFCs and plays a role in transferring OH^-The ion and fuel permeation barrier function determine the performance of the fuel cell.

Recent studies have shown that most anion exchange membranes are based on common random polymers, and highly toxic carcinogenic chloromethyl ether reagents are used in the preparation process. The stability and ionic conductivity of the AEMs are insufficient at present, so that the application of the AEMFC is limited. The obvious microphase separation membrane structure can promote the construction of an ion transfer channel and improve OH^-Electrical conductivity. Conventional wisdom holds that ionic conductivity can be increased by increasing the Ion Exchange Capacity (IEC). There have been groups that grafted a tertiary amine onto Quaternary Ammonium Polysulfone (QAPS) to obtain stable ionic solutions and crosslinked membranes. In this self-polymerizing design, the attachment of long alkyl side chains to the QAPS effectively promotes microphase separation of the hydrophilic/hydrophobic regions, promoting ion channel formation and aggregation. The prepared QAPS has an ion conductivity 3 times higher than that of the conventional one,comparable to Nafion membranes at high temperatures. In addition, there is another new approach to increase ionic conductivity by increasing ionic mobility, by grafting hydrophobic side chains onto quaternized polyphenylene oxide (QAPPO) to control the film microstructure. The method can promote the micro-phase separation of the hydrophilic/hydrophobic regions and construct good ion channels. However, this membrane has an excessively high ion exchange capacity, and is likely to undergo severe swelling, impairing dimensional stability, resulting in a decrease in mechanical strength, and thus is difficult to put into practical use.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention aims to provide an anion exchange membrane containing dense ion string block type and a preparation method thereof, wherein a chloromethyl ether reagent is not used in the preparation process. By means of molecular design, the ion strings are densely grafted on the hydrophilic section to serve as functional groups, and benzonitrile groups are grafted on the hydrophobic section, so that the anion exchange membrane has the characteristics of good space structure, developed ion transmission channels, high water content and low swelling, and shows higher ion conductivity and better fuel cell performance.

One of the technical schemes adopted by the invention for solving the technical problems is as follows:

a block type anion exchange membrane containing dense ion strings comprises four benzyl structures in a hydrophilic section, a plurality of ion strings are grafted, and each ion string contains two or more than two cationic groups; the hydrophobic section of the organic silicon polymer contains a suspended benzonitrile structure. The molecular structural formula is as follows:

wherein m is an integer of 5 to 50, n is an integer of 5 to 50, R is H, Br or a structure of

And at least one R isOne of (1);

in the present invention, the "at least one R is One of these "can mean that for each monomer in the polymer, there is at least one of the three ion strings per monomer, or that there is an average of at least one of the three ion strings per monomer, in terms of the degree of substitution of R in the polymer.

When two or more R's are

In the case of (3), each R may be the same or different.

P₁At least one selected from (a1) to (e 1); p₂At least one selected from (a1) to (e 1). P₁And P₂May be the same or different cell structures.

Ar is selected from at least one of (a2) to (e 2).

The second technical scheme adopted by the invention for solving the technical problems is as follows:

a preparation method of a block type anion exchange membrane containing dense ion strings specifically comprises the following steps:

1) synthesis of hydrophilic chain segment oligomer: will utensilHas P₁The tetramethyl bisphenol monomer with the structure and the dihalogen monomer with the Ar structure are fed in a molar ratio of m (m-1) under the protection of nitrogen and are equivalent to the monomer with P₁Dissolving a tetramethyl bisphenol monomer with a structure in a polar aprotic solvent in the presence of anhydrous potassium carbonate and toluene, wherein the anhydrous potassium carbonate is 1.5-5 times of the molar weight of the tetramethyl bisphenol monomer, reacting for 4-6 h at 130-150 ℃, heating to 160-170 ℃ for 10-12 h, and adding 0.04-0.06 m of P₁And (3) continuously reacting the structural tetramethyl bisphenol monomer at 160-170 ℃ for 1-2 h, cooling, precipitating with an alcohol-water solution, filtering, washing and drying to obtain the hydrophilic chain segment oligomer.

2) Synthesis of hydrophobic segment oligomer: will have P₂Bisphenol monomer and 3, 5-dichlorobenzonitrile monomer of the structure are fed in a molar ratio of n (n +1), protected by nitrogen and equivalent to P₂Dissolving a bisphenol monomer with a structure in a polar aprotic solvent in the presence of anhydrous potassium carbonate and toluene, wherein the anhydrous potassium carbonate is 1.5-5 times the mol of the bisphenol monomer, reacting at 130-145 ℃ for 3-5 hours, heating to 150-160 ℃ for reacting for 8-10 hours, adding 0.04-0.06 n mol of 3, 5-dichlorobenzonitrile monomer, continuing to react at 150-160 ℃ for 0.4-0.6 hour, cooling, precipitating with an alcohol-water solution, filtering, washing, and drying to obtain the hydrophobic chain segment oligomer.

3) Synthesis of Block copolymer: feeding the prepared hydrophilic chain segment oligomer and hydrophobic chain segment oligomer in an equimolar ratio, dissolving the hydrophilic chain segment oligomer and the hydrophobic chain segment oligomer in a polar aprotic solvent under the protection of nitrogen and in the presence of anhydrous potassium carbonate and toluene which are 1-100 times the moles of the hydrophilic chain segment oligomer, reacting for 5-6 h at 140-150 ℃, heating to 160-180 ℃ for reacting for 20-24 h, cooling, precipitating with an alcohol-water solution, filtering, washing and drying to obtain the block copolymer.

4) Synthesis of bromomethylated Block copolymer: dissolving the block copolymer obtained in the step 3) in 1,1,2, 2-tetrachloroethane, then adding N-bromosuccinimide and an initiator, reacting for 3-8 h at 84-86 ℃, cooling, precipitating with methanol, filtering, washing, and drying to obtain the bromomethylation block copolymer. The anion exchange membranes with different bromination degrees can be synthesized by changing the charge ratio of the brominating agent to the block copolymer.

5) Preparation of anion exchange membrane: dissolving the bromomethylation segmented copolymer obtained in the step 4) in DMSO, slowly adding an ion-containing string quaternizing agent with an R structure, dissolving and reacting for 18-48 h at 30-60 ℃, finally coating the membrane casting solution on a substrate, heating to volatilize the solvent to obtain a solid membrane, immersing the solid membrane in alkali liquor, reacting for 24-48 h, and fully washing with deionized water to obtain the compact ion-containing string block type anion exchange membrane.

In one embodiment: said has P₁The tetramethylbisphenol monomer of structure includes at least one of 4,4 '-methylenebis (2, 6-dimethyl) phenol, 2-bis (4-hydroxy-3, 5-dimethylphenyl) propane, α' -bis (4-hydroxy-3, 5-dimethylphenyl) -1, 4-diisopropylbenzene, 3 '-bis (4-hydroxy-3, 5-dimethylphenyl) phenolphthalein, 3-bis (4-hydroxy-3, 5-dimethylphenyl) phthalein, or 9,9' -bis (4-hydroxy-3, 5-dimethylphenyl) fluorene.

In one embodiment: said has P₂Bisphenol monomers of structure include phenolphthalein.

In one embodiment: the dihalo monomer with the Ar structure comprises at least one of 4,4 '-dichlorodiphenyl sulfone, 4' -dichlorobenzophenone, 4 '-dichlorodiphenylmethane, 4' -dichlorobiphenyl or 3, 5-dichlorobenzonitrile.

In one embodiment: the polar aprotic solvent includes at least one of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, or dimethylsulfoxide.

In one embodiment: in the step 4), the molar ratio of the block copolymer, the N-bromosuccinimide and the initiator is 1 (10-100) to 0.5-5.

In one embodiment: the initiator comprises at least one of azobisisobutyronitrile or benzoyl peroxide.

In one embodiment: the ion-containing cluster quaternizing agent comprises at least one of 6- (dimethylamino) -N, N, N-trimethylhexane-1-ammonium bromide, 6- (dimethylamino) -N-ethyl-N, N-dimethylhexane-1-ammonium bromide, 1- (N ', N' -dimethylamino) -6,12- (N, N, N-trimethylammonium) dodecylammonium bromide and the like.

In one embodiment: in the step 5), the molar ratio of benzyl bromide groups in the bromomethylation segmented copolymer to the quaternizing agent is 1 (1-6).

In one embodiment: the alkali liquor comprises at least one of potassium hydroxide solution or sodium hydroxide solution.

In one embodiment: the aqueous alcohol solution includes an aqueous methanol solution.

In one embodiment: the substrate comprises a polytetrafluoroethylene sheet or a glass sheet.

In the structural formula of the present invention, the linking site with the polymer main chain is represented by a wavy line.

The "hydrophilic segment" according to the present invention refers to a portion having hydrophilicity in a block copolymer of an anion-exchange membrane, and the "hydrophilic segment" refers to one of raw materials for synthesizing the block copolymer, and the structure of the "hydrophilic segment" corresponds to that of the "hydrophilic segment" in the block copolymer.

The "hydrophobic segment" according to the present invention means a portion having hydrophobicity in a block copolymer of an anion-exchange membrane, and the "hydrophobic segment" means one of raw materials for synthesizing the block copolymer, and the structure of the "hydrophobic segment" corresponds to that of the "hydrophobic segment" in the block copolymer.

The dense method refers to that up to four ion strings R can be introduced into a benzyl active site of a main chain, and each ion string R contains a plurality of ion exchange groups.

The "ion string" of the present invention refers to a structure of R containing two or more cationic groups.

The equipment, reagents, processes, parameters and the like related to the invention are conventional equipment, reagents, processes, parameters and the like except for special description, and no embodiment is needed.

All ranges recited herein include all point values within the range.

The invention has the advantages that:

1. ion strings with high mobility and high ion density are densely grafted on the hydrophilic section through molecular design, so that the membrane presents obvious microphase separation, and a continuous and effective OH-ion transmission channel is formed. In addition, the benzonitrile group with strong polarity is hung on the hydrophobic segment, so that the swelling resistance of the membrane is enhanced. The anion exchange membrane prepared by the method has high water content and low swelling ratio.

2. The preparation method adopts a bromomethylation method, and avoids the use of a highly toxic and highly carcinogenic chloromethyl ether reagent in the preparation process of a common anion exchange membrane.

3. The hydrophilic section of the membrane contains four functionalized benzyl active sites, can be grafted on an ion string, and each ion string contains two or more cationic groups, so that bromination reaction and quaternization reaction can be controlled at designed positions, the positions and the number of ion exchange groups of the membrane can be accurately controlled, and the microstructure and the performance of the membrane can be controlled.

4. The prepared anion exchange membrane simultaneously has high water content, high conductivity and low swelling ratio, has good chemical stability and thermal stability, and shows excellent fuel cell performance.

Drawings

FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of the block copolymer prepared in example 1.

FIG. 2 is a Fourier transform infrared spectrum of the anion exchange membrane prepared in example 1.

FIG. 3 is an atomic force microscope scan of the anion exchange membrane prepared in example 1.

FIG. 4 is a thermogravimetric analysis plot of the anion exchange membrane prepared in example 1.

Detailed Description

In order to more clearly illustrate the present invention, the present invention will be further described with reference to the following examples and the accompanying drawings.