阅读说明：本技术 一种含密集柔性离子串的阴离子交换膜及其制备方法 (Anion exchange membrane containing dense flexible ion strings and preparation method thereof ) 是由 赖傲楠 王贞 胡鹏程 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柔性离子串的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包含酚酞侧基的聚合物主链结构上密集接枝了含多个离子基团的柔性离子串作为功能基团。其制备过程主要包括：(1)含四个苯甲基基团的酚酞基聚合物的制备；(2)对聚合物上的苯甲基进行溴化改性；(3)含密集柔性离子串的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,具备高离子电导率以及低溶胀率特性,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 an anion exchange membrane containing a dense flexible ion string and a preparation method thereof, which can be used for an alkaline fuel cell. The anion exchange membrane is structurally characterized in that flexible ion strings containing a plurality of ion groups are densely grafted on a polymer main chain structure containing phenolphthalein side groups and serve as functional groups. The preparation process mainly comprises the following steps: (1) preparing a phenolphthalein-based polymer containing four benzyl groups; (2) carrying out bromination modification on benzyl on the polymer; (3) and (3) preparing an anion exchange membrane containing dense flexible ion strings. The anion exchange membrane prepared by the invention has a developed ion transmission channel, has the characteristics of high ion conductivity and low swelling rate, does not use a highly toxic and carcinogenic chloromethyl ether reagent in the preparation process, and has wide application prospect in the field of alkaline fuel cells.)

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

wherein x is 0.1 to 1 and at least one R is

Ar₁at least one selected from (a) to (e); ar (Ar)₂At least one selected from (a) to (e);

2. the preparation method of the anion exchange membrane containing the dense flexible ion string, which is characterized by comprising the following steps: the method comprises the following steps:

1) synthesis of Polymer: mixing x parts of 3,3-Bis (4-hydroxy-3, 5-dimethylphenyl) phthalide with x parts of Ar₁Feeding a difluoro monomer with a structure in an equimolar ratio, dissolving the difluoro monomer in a polar aprotic solvent under the protection of nitrogen and in the presence of anhydrous potassium carbonate and toluene which are 1.5-10 times the mol of 3, 3-bis (4-hydroxy-3, 5-dimethylphenyl) phthalide, reacting for 4-6 h at 140-150 ℃, heating to 160-180 ℃ for 10-12 h, and cooling the reaction solution to room temperature; then 1-x parts of phenolphthalein and 1-x parts of Ar₂Adding a difluoro monomer with a structure into the reaction solution according to an equimolar ratio, raising the temperature to 140-150 ℃, reacting for 3-5 h, raising the temperature to 160-180 ℃, continuing to react for 6-10 h, stopping the reaction, cooling to room temperature, precipitating with an alcohol-water solution, filtering, washing and drying to obtain a polymer;

2) synthesis of brominated polymer: dissolving the polymer obtained in the step 1) in 1,1,2, 2-tetrachloroethane, then adding N-bromosuccinimide and an initiator, reacting for 4-6 h at 84-86 ℃, cooling, precipitating with methanol, filtering, washing, and drying to obtain a brominated polymer;

3) preparation of anion exchange membrane: dissolving the brominated polymer obtained in the step 2) in DMSO, adding an excessive quaternizing agent with an R structure, and reacting at 40-50 ℃ for 12-24 h to obtain a casting solution; coating the obtained casting solution on a substrate, and heating to volatilize the solvent to obtain a solid film; and then immersing the solid membrane into alkali liquor for ion exchange for 24-48 h, and fully washing with water to obtain the anion exchange membrane containing the dense flexible ion strings.

3. The method for preparing the anion-exchange membrane containing the dense flexible ion strings according to claim 2, wherein the method comprises the following steps: said has Ar₁The difluoro monomer with the structure comprises at least one of 4,4' -difluorobenzophenone, 4' -difluorobiphenyl, 4' -difluorodiphenyl sulfone, 2, 6-difluorobenzonitrile, 4' -difluorodiphenylmethane or 4,4' -difluorobiphenyl.

4. The method for preparing the anion-exchange membrane containing the dense flexible ion strings according to claim 2, wherein the method comprises the following steps: said has Ar₂Difluoro of structureThe monomer comprises at least one of 4,4' -difluorobenzophenone, 4' -difluorobiphenyl, 4' -difluorodiphenylsulfone, 2, 6-difluorobenzonitrile, 4' -difluorodiphenylmethane or 4,4' -difluorobiphenyl.

5. The method for preparing the anion-exchange membrane containing the dense flexible ion strings according to claim 2, wherein the method comprises the following steps: the polar aprotic solvent includes at least one of dimethyl sulfoxide, N-dimethylacetamide, N-dimethylformamide, or N-methylpyrrolidone.

6. The method for preparing the anion-exchange membrane containing the dense flexible ion strings according to claim 2, wherein the method comprises the following steps: in the step 2), the molar ratio of the polymer to the N-bromosuccinimide to the initiator is 1: (0.1-1.5): (0.01-0.075).

7. The method for preparing the anion-exchange membrane containing the dense flexible ion strings according to claim 2, wherein the method comprises the following steps: the initiator comprises at least one of benzoyl peroxide or azobisisobutyronitrile.

8. The method for preparing the anion-exchange membrane containing the dense flexible ion strings according to claim 2, wherein the method comprises the following steps: the quaternizing agent having the structure R 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 the anion-exchange membrane containing the dense flexible ion strings according to claim 2, wherein the method comprises the following steps: in the step 3), the alkali liquor comprises at least one of a sodium hydroxide solution or a potassium hydroxide solution.

10. The method for preparing the anion-exchange membrane containing the dense flexible ion strings according to claim 2, wherein the method comprises the following steps: the aqueous alcohol solution comprises an aqueous methanol solution; the substrate comprises a glass plate or a polytetrafluoroethylene plate.

Technical Field

The invention belongs to the field of membrane science and technology, 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 a Fuel and an oxidant into electrical energy by using a chemical reaction, has the advantages of high efficiency, high energy density, environmental friendliness, portability, and the like, and is regarded as a fourth generation power generation technology. At present, alkaline Anion Exchange Membrane Fuel Cells (AEMFCs) taking Anion Exchange Membranes (AEMs) as polyelectrolytes are concerned due to the characteristics of high reaction activity of cell electrodes, capability of using non-noble metal electrode catalysts, low corrosiveness and the like, and become research hotspots in the field of fuel cells at present. Wherein, the anion exchange membrane is a key component of AEMFCs and plays a role in conducting OH^-The ion and fuel permeation barrier function determine the performance of the fuel cell.

In recent years, researches show that a good microphase separation membrane structure can promote the construction of an ion conduction channel and improve the conductivity of hydroxide. For example, several "blocky" AEMs prepared by incorporating basic functional groups into the hydrophilic segment of a block copolymer exhibit distinct hydrophilic/hydrophobic microphase structures with higher conductivity. Still many researchers have constructed "side-chain" AEMs by another effective method of improving microphase separation, i.e., grafting ion-conducting groups onto the side chains and separating them from the polymer backbone, such as one-step benzene modification of industrial Polyetheretherketone (PEEK). And researchers have reported that aggregation of conductive groups can be further enhanced to obtain high performance by having a plurality of ion conductive groups on flexible side chains. Current AEMs have insufficient stability and ionic conductivity, limiting their application in AEMFCs. By increasing the Ion Exchange Capacity (IEC) of the AEMs, the ion conductivity of the AEMs can be increased. However, AEMs have too high an ion exchange capacity, are prone to severe swelling, impair dimensional stability, and cause a decrease in mechanical strength, resulting in a failure in practical use.

Disclosure of Invention

In order to overcome the above-mentioned disadvantages and shortcomings of the prior art, the present invention is directed to synthesis of anion exchange membranes containing dense flexible ion strings without using chloromethyl ether reagents in their preparation. The flexible ion strings are densely grafted to the phenolphthalein unit structure of the polymer through molecular design, so that the formation of a phase separation structure is promoted, the prepared anion exchange membrane has developed ion transfer channels and the characteristics of high water content and low swelling, shows higher ionic conductivity and better fuel cell performance, and has wide application prospect in the field of alkaline fuel cells.

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

the anion exchange membrane comprises a polymer main chain containing a phenolphthalein side group and a plurality of flexible ion strings densely grafted on the polymer main chain structure containing the phenolphthalein side group, wherein each ion string contains two or more than two cationic groups. The molecular structural formula is as follows:

wherein x is 0.1-1, R is H, Br or structure

And at least one R isOne of (1);

in the present invention, the "at least one R is

By one of "can be meant that for each monomer in the polymer, there is at least one R on each monomer that is one of three ion stringsIt may also mean that, in terms of the degree of substitution of R in the polymer, there is on average at least one R per monomer in one of the three ion strings.

When two or more R's are

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

Ar₁At least one selected from (a) to (e), Ar₂At least one selected from (a) to (e). Ar (Ar)₁And Ar₂May be the same or different cell structures.

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

a preparation method of an anion exchange membrane containing a dense flexible ion string specifically comprises the following steps:

1) synthesis of Polymer: mixing x parts of 3, 3-bis (4-hydroxy-3, 5-dimethylphenyl) phthalide and x parts of a mixture containing Ar₁Feeding a difluoro monomer with a structure in an equimolar ratio, dissolving the difluoro monomer in a polar aprotic solvent under the protection of nitrogen and in the presence of anhydrous potassium carbonate and toluene which are 1.5-10 times the mol of 3, 3-bis (4-hydroxy-3, 5-dimethylphenyl) phthalide, reacting for 4-6 h at 140-150 ℃, heating to 160-180 ℃ for 10-12 h, and cooling the reaction solution to room temperature; then 1-x parts of phenolphthalein and 1-x parts of Ar₂Feeding a difluoro monomer with a structure in an equimolar ratio, adding the difluoro monomer into the reaction solution, raising the temperature to 140-150 ℃, reacting for 3-5 h, raising the temperature to 160-180 ℃, continuing to react for 6-10 h, stopping the reaction, cooling to room temperature, precipitating with an alcohol-water solution, filtering, washing and drying to obtain the polymer.

2) Synthesis of brominated polymer: dissolving the polymer obtained in the step 1) in 1,1,2, 2-tetrachloroethane, then adding N-bromosuccinimide and an initiator, reacting for 4-6 h at 84-86 ℃, cooling, precipitating with methanol, filtering, washing, and drying to obtain the brominated polymer. The charge ratio of brominating agent to polymer is changed to synthesize the brominated polymer with different bromination degree.

3) Preparation of anion exchange membrane: dissolving the brominated polymer obtained in the step 2) in DMSO, slowly adding an excessive ion-containing cluster quaternizing agent with an R structure, and reacting at 40-50 ℃ for 12-24 h to obtain a membrane casting solution. And coating the obtained casting solution on a substrate, and heating to volatilize the solvent to obtain the solid film. And then immersing the solid membrane into alkali liquor for ion exchange for 24-48 h, and fully washing with deionized water to obtain the anion exchange membrane containing the dense flexible ion strings.

Further, the compound has Ar₁The difluoro monomer with the structure comprises at least one of 4,4' -difluorobenzophenone, 4' -difluorobiphenyl, 4' -difluorodiphenyl sulfone, 2, 6-difluorobenzonitrile, 4' -difluorodiphenylmethane or 4,4' -difluorobiphenyl.

Further, the compound has Ar₂The difluoro monomer with the structure comprises at least one of 4,4' -difluorobenzophenone, 4' -difluorobiphenyl, 4' -difluorodiphenyl sulfone, 2, 6-difluorobenzonitrile, 4' -difluorodiphenylmethane or 4,4' -difluorobiphenyl.

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

Further, the molar ratio of the polymer to the N-bromosuccinimide to the initiator is 1: (0.1-1.5): (0.01-0.075).

Further, the initiator comprises at least one of benzoyl peroxide and azobisisobutyronitrile.

Further, the ion-containing cluster quaternizing agent with the R structure 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.

Further, the lye comprises at least one of a potassium hydroxide solution or a sodium hydroxide solution.

Further, the aqueous alcohol solution includes an aqueous methanol solution.

Further, the substrate comprises a glass plate or a teflon plate.

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

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

The term "flexibility" as used herein refers to the flexibility of the chain due to the fact that the structure of R has a carbon chain with a certain length, which results in a large number of conformations and a good possibility of curling.

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

The room temperature, namely the normal environment temperature, can be 10-30 ℃.

The parts are mole parts unless otherwise specified.

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) the anion exchange membrane is prepared by densely grafting the flexible ion strings with high ion density on the polymer, so that the microstructure of the membrane is controllable, the membrane has an obvious microphase separation structure, and the membrane is promoted to form a continuous and effective OH-ion transmission channel.

2) Rigid and large steric hindrance phenolphthalein side groups are introduced to the polymer membrane through molecular design, so that the water retention capacity of the membrane is enhanced, the formation of an ion transmission channel is promoted, and the high water content of the anion exchange membrane is realized.

3) 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. By changing the charge ratio of the brominating reagent to the polymer, the brominated polymer with different bromination degree can be synthesized.

4) The polymer chain contains a tetramethylphenolphthalein unit structure and four bromination active sites, so that bromination reaction and quaternization reaction can be controlled at designed positions, and the positions and the number of ion exchange groups of the membrane can be accurately controlled. In addition, four flexible ion strings can be densely introduced into one tetramethylphenolphthalein unit at most, and each ion string contains a plurality of ion exchange groups, so that the design improves the density and the aggregation degree of functional groups of the membrane, improves the ion exchange capacity and is beneficial to improving the conductivity of the membrane.

5) 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 NMR spectrum of the anion exchange membrane prepared in example 1.

FIG. 2 is an atomic force microscope scan of the anion exchange membrane prepared in example 1.

FIG. 3 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.