CN111875827A

CN111875827A - Phenolphthalein-based anion exchange membrane containing comb-shaped side chain and preparation method thereof

Info

Publication number: CN111875827A
Application number: CN202010761639.7A
Authority: CN
Inventors: 赖傲楠; 王贞; 胡鹏程; 周树锋
Original assignee: Huaqiao University
Current assignee: Huaqiao University
Priority date: 2020-07-31
Filing date: 2020-07-31
Publication date: 2020-11-03

Abstract

The invention discloses a phenolphthalein anion-exchange membrane containing a comb-shaped side chain and a preparation method thereof, and the phenolphthalein anion-exchange membrane can be used for an alkaline fuel cell. The anion exchange membrane is made of a phenolphthalein-based polyarylether polymer containing comb-shaped side chains, and is characterized in that an imidazole ion group containing a flexible long carbon chain is grafted on a phenolphthalein structural unit. The preparation process mainly comprises the following steps: (1) synthesizing a phenolphthalein-based polyarylether polymer; (2) bromination modification of the polymer; (3) preparing the phenolphthalein anion-exchange membrane containing the comb-shaped side chain. 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 be obtained at the same time 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.

Description

Phenolphthalein-based anion exchange membrane containing comb-shaped side chain and preparation method thereof

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 a Fuel and an oxidant into electrical energy using a chemical reaction technology, and is considered as a fourth generation power generation technology. As a clean and efficient renewable energy conversion device, the fuel cell has the advantages of high efficiency, high energy density, environmental friendliness, convenience in carrying and the like, and has attracted extensive attention in the past decade. Among various types of fuel cells, alkaline Anion Exchange Membrane Fuel Cells (AEMFCs) have received particular attention due to their high redox reaction rates and potential for use of non-noble metal catalysts, and have become a research hotspot in the field of fuel cells at present. Among them, Anion Exchange Membranes (AEMs) are key components of AEMFCs, which function to conduct OH^-The ion and fuel permeation barrier function determine the performance of the fuel cell.

Recent studies have shown that the construction of an hydrophilic/hydrophobic microphase separation structure is an effective strategy for forming a continuous ion transport channel and improving ion conductivity. Microphase separation can be achieved in both block type (ion exchange groups on the block backbone) and side chain type AEMs (ion exchange groups grafted on the side chains). Because most of anion exchange membranes are based on common random polymers, the common random anion exchange membranes can have higher ion exchange capacity, but because the membrane materials are based on the common random polymers, the swelling resistance is poorer, the swelling of the membrane is correspondingly increased while the water content and the conductivity of the membrane are increased, the mechanical strength of the final membrane is reduced, and the performance of the fuel cell is reduced. Furthermore, inspired by the Nafion structure, comb AEMs are of great interest to many researchers,in such AEMs, the ion exchange groups are grafted onto side chains. Anion exchange membranes have been prepared by the research group by synthesizing comb copolymers, which exhibit higher conductivity and mechanical properties than random polymer membranes, but still have poor resistance to swelling at high ion exchange capacity. In these comb-like AEMs, nanoscale ion clusters within the membrane form distinct microphase-separated structures. In addition, the size and basic stability of the AEMs can also be improved due to the hydrophobic and steric effects of the long alkyl side chains. For example, researchers have designed and synthesized a series of comb-like polysulfones AEMs with long alkyl side chains. The obtained AEMs have ordered ion aggregation structure and continuous effective OH^-Ion transport channels, high conductivity, low swelling, excellent mechanical and chemical stability. However, in most cases, researchers still employ methods that increase the number of ion exchange groups in the polymer chain, further enhancing the microphase separation between hydrophilic ion clusters and hydrophobic domains. AEMs also tend to swell severely and have reduced dimensional stability under conditions of high ion exchange capacity. Existing anion exchange membranes still face several challenges, such as a trade-off between dimensional stability and electrical conductivity. These result in anion exchange membranes that face great challenges in industrial practice.

Disclosure of Invention

In order to overcome the above disadvantages and shortcomings of the prior art, the present invention aims to provide a phenolphthalein-based anion-exchange membrane containing comb-shaped side chains and a preparation method thereof, wherein a chloromethyl ether reagent is not used in the preparation process. The polymer chain is introduced with a phenolphthalein group through molecular design, and an imidazole functional group containing a comb-shaped long alkyl side chain is introduced on a phenolphthalein unit, so that the membrane has the characteristics of developed ion transmission channels, high water content and low swelling degree, and shows higher ionic conductivity and better fuel cell performance.

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

a molecular structure of the phenolphthalein-based anion-exchange membrane containing comb-shaped side chains comprises a polymer chain segment containing phenolphthalein groups, for example, a main chain structure is a phenolphthalein-based polyarylether polymer, and an imidazole ion functional group containing flexible comb-shaped long alkyl side chains is grafted on a phenolphthalein structural unit, and the molecular structural formula is as follows:

wherein x is 0-1, R is H, Br or structure

And at least one R is one of imidazole ionic groups containing flexible long carbon chains

One of (1);

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

One of the above "may mean that for each monomer in the polymer, at least one R per monomer is one of several imidazolium groups containing flexible long carbon chains, or that for the degree of substitution of R in the polymer, on average at least one R per monomer is one of several imidazolium groups containing flexible long carbon chains.

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); ar (Ar)₂At 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 a phenolphthalein-based anion-exchange membrane containing a comb-shaped side chain specifically comprises the following steps:

1) synthesis of phenolphthalein-based polymer: 1 part of o-tolylphenolphthalein and x parts of a solvent containing Ar₁Dihalo monomer of structure and 1-x parts of Ar₂Putting a dihalogen monomer with the structure into a reaction kettle, dissolving the dihalogen monomer in a polar aprotic solvent under the protection of nitrogen and in the presence of anhydrous potassium carbonate with the molar weight 2.5-3 times of that of o-tolylphenolphthalein and toluene, reacting at 135-145 ℃ for 3-5 h, heating to 150-170 ℃ for 16-24 h, stopping the reaction, cooling to room temperature, precipitating with an alcohol-water solution, filtering, washing and drying to obtain the phenolphthalein-based polymer.

2) Synthesis of brominated polymer: dissolving the phenolphthalein-based 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. By varying the feed ratio of brominating agent to polymer, brominated polymers of varying degrees of bromination can be obtained.

3) Preparation of anion exchange membrane: dissolving the brominated polymer obtained in the step 2) in DMSO, slowly adding an imidazole functional reagent containing a flexible long carbon chain with an R structure, and reacting at 40-50 ℃ for 24-48 h to obtain a casting solution; coating the casting solution on a substrate, and heating to volatilize the solvent to obtain a solid film. And finally, soaking the solid film in alkali liquor, reacting for 24-48 h, and then fully washing with deionized water to obtain the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain.

In one embodiment: said has Ar₁The dichloro monomer with the structure comprises 4,4 '-dichlorodiphenyl sulfone, 4' -dichlorobenzophenone,4,4' -dichlorodiphenylmethane, 4' -dichlorobiphenyl, 3' -dichlorobiphenyl or 3, 5-dichlorobenzonitrile.

In one embodiment: said has Ar₂The dichloro monomer with the structure comprises at least one of 4,4' -dichlorodiphenyl sulfone, 4' -dichlorobenzophenone, 4' -dichlorodiphenylmethane, 4' -dichlorobiphenyl, 3' -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 2), the molar ratio of the phenolphthalein-based polymer to the N-bromosuccinimide to the initiator is 1: (2-5): (0.1-0.25).

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

In one embodiment: the imidazole functionalization reagent containing the flexible long carbon chain is at least one of 1-amyl imidazole, 1-octyl imidazole, 1-dodecyl imidazole, 1-decyl-2-methyl imidazole and the like.

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 glass plate or a polytetrafluoroethylene plate.

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

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 comb-shaped structure refers to a zigzag-like structure formed by carbon chains with certain lengths in R.

In the invention, 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. rigid and large-steric-hindrance phenolphthalein group structures are introduced to polymer chains through molecular design, and long alkyl chains are introduced to phenolphthalein units to form compact comb-shaped structures. On the one hand, the membrane has an obvious microphase separation structure, realizes the controllability of the microstructure of the membrane and is beneficial to forming a continuous and effective OH-ion transmission channel; on the other hand, the water retention capacity and the swelling resistance of the membrane are enhanced. Therefore, the defect that the existing anion exchange membrane cannot be obtained at the same time of high ionic conductivity, high water content and low swelling ratio is overcome.

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. A dimethyl phenolphthalein structural unit is introduced to a polymer chain through molecular design, and the polymer chain contains a brominated benzyl active site, so that bromination reaction and quaternization reaction can be controlled at designed positions. Therefore, the position and the number of the ion exchange groups of the membrane can be accurately controlled, and the membrane structure and the membrane performance 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 phenolphthalein-based polymer prepared in example 1.

FIG. 2 is a NMR 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.

Example 1

In this embodiment, taking a long-carbon-chain comb-shaped phenolphthalein-based polyarylethersulfone nitrile anion-exchange membrane containing 10 carbon atoms (the proportion of sulfone segments is 40%) as an example, the structural formula is as follows:

wherein R is H or

The preparation method comprises the following steps:

1) synthesis of Polymer: 1.149g of 4,4' -dichlorodiphenyl sulfone (4mmol), 1.032g of 3, 5-dichlorobenzonitrile (6mmol), 3.465g of o-tolylphenolphthalein (10mmol), 3.784g of anhydrous potassium carbonate (27.4mmol) and 10mL of toluene are dissolved in 30mLN, N-dimethylacetamide, and the mixture is reacted for 4 hours at 145 ℃ under the protection of nitrogen, then heated to 170 ℃ for reaction for 20 hours, and after cooling, precipitated, filtered, washed and dried by 400mL of methanol aqueous solution (the volume ratio of methanol to water is 1:1), thus obtaining the phenolphthalein-based polymer.

2) Synthesis of bromomethylated polymers: 1g (2.04mmol) of phenolphthalein-based polymer was dissolved in 30mL of 1,1,2, 2-tetrachloroethane, followed by addition of 0.783g (4.4mmol) of N-bromosuccinimide and 0.0711g (0.29mmol) of benzoyl peroxide, reaction at 85 ℃ for 5 hours, cooling, precipitation with methanol, filtration, washing, and drying to give a bromomethylated polymer.

3) Preparation of anion exchange membrane: dissolving 1g of bromomethylated phenolphthalein-based polymer in 30mL of dimethyl sulfoxide, slowly adding 0.701g (3.15mmol) of 1-decyl-2-methylimidazole containing a flexible long carbon chain as an imidazole functionalization reagent, reacting at 45 ℃ for 36h, coating the casting solution on a glass plate, heating to volatilize a solvent to obtain a solid film, finally soaking the film in 0.1mol/L potassium hydroxide alkali liquor, reacting for 48h, and fully washing with deionized water to obtain the pectinated phenolphthalein-based polyarylethersulfone nitrile anion exchange film.

4) And (3) testing: the structures of the phenolphthalein-based polymer and the anion exchange membrane are determined by a nuclear magnetic resonance technology. The phase separation structure and ion transport channels of the membrane were observed by atomic force microscopy. The ion exchange capacity of the membranes was tested by back titration. The water content and swelling ratio of the film at 30 ℃ and 80 ℃ were measured. The ionic conductivity of the membrane was measured with an ac impedance meter. The thermal stability of the prepared anionic membrane was measured under an N2 atmosphere with a thermogravimetric analyzer. The prepared anionic membranes were soaked in 1m koh solution at 80 ℃ to test the chemical stability of the membranes. 5) And (3) testing results: the chemical structures of the phenolphthalein-based polymer (FIG. 1) and the anionic membrane (FIG. 2) were confirmed by NMR techniques. The prepared anion exchange membrane forms a remarkable hydrophilic/hydrophobic microphase separation structure and a developed OH & lt- & gt ion transmission channel (figure 3). Theoretical value of ion exchange capacity of 1.84mmol g^-1The test value was 1.61 mmoleg^-1. The water contents of the film at 30 ℃ and 80 ℃ were 23.6% and 29.3%, and the swelling of the film at 30 ℃ and 80 ℃ was 7.5% and 9.8%. The ionic conductivity of the membrane at 30 ℃ and 80 ℃ is 34.8mS cm^-1And 73.7mS · cm^-1. From the thermal decomposition curve of the film (fig. 4), the thermal decomposition temperature of the film was 201 ℃ or higher, indicating that the film had good thermal stability. The membrane is soaked in 1MKOH solution at 80 ℃ for 500h, the ionic conductivity can be kept over 88 percent, and good chemical stability is shown.

Example 2

In this embodiment, taking a long carbon chain comb-shaped phenolphthalein based polyaryletherketone nitrile anion-exchange membrane containing 10 carbon atoms (the proportion of ketone segments is 20%) as an example, the structural formula is as follows:

wherein R is H or

The preparation method comprises the following steps:

1) synthesizing a phenolphthalein polyaryletherketone nitrile polymer: 3, 5-dichlorobenzonitrile (8mmol, 1.376g), o-tolylphenolphthalein (10mmol, 3.465g), 4' -dichlorobenzophenone (2mmol, 0.5024g), 3.932g (28.4mmol) anhydrous potassium carbonate and 10mL of toluene are dissolved in 30mL of polar aprotic solvent N, N-dimethylformamide, reacted for 4 hours at 145 ℃ under the protection of nitrogen, heated to 170 ℃ and reacted for 20 hours, and precipitated, filtered, washed and dried by 400mL of methanol aqueous solution (the volume ratio of methanol to water is 1:1) after cooling to obtain the polyaryletherketone nitrile polymer.

2) Synthesis of bromomethylated polymers: after dissolving 1g (2.2mmol) of the polymer in 30mL of 1,1,2, 2-tetrachloroethane, 0.784(4.4mmol) of g N-bromosuccinimide and 0.0731g (0.30mmol) of benzoyl peroxide were added, the mixture was reacted at 85 ℃ for 5 hours, and after cooling, the bromomethylated polymer was obtained by precipitation with methanol, filtration, washing and drying.

3) Preparation of anion exchange membrane: dissolving 1g of bromomethylated polymer in 30mL of DMSO, slowly adding 0.717g (3.22mmol) of 1-decyl-2-methylimidazole containing a flexible long carbon chain as an imidazole functionalized reagent, reacting at 45 ℃ for 36h, coating the casting solution on a glass plate, heating to volatilize a solvent to obtain a solid membrane, finally soaking the solid membrane in 0.1mol/L potassium hydroxide alkali liquor, reacting for 48h, and fully washing with deionized water to obtain the pectinate phenolphthalein polyaryletherketone nitrile anion exchange membrane.

4) And (3) testing results: the prepared anion exchange membrane forms a remarkable hydrophilic/hydrophobic microphase separation structure and a developed OH-ion transmission channel. Theoretical value of ion exchange capacity of 1.92mmol g^-1The test value was 1.65mmol g^-1. The water content of the film at 30 ℃ and 80 ℃ was 21.9% and 27.1%, and the swelling of the film at 30 ℃ and 80 ℃ was 6.8% and 9.2%. The ionic conductivity of the membrane at 30 ℃ and 80 ℃ is 40.2mS cm^-1And 83 mS. cm^-1. The resulting film was tested for thermal decomposition temperatures above 203 c, indicating that the film had good thermal stability. The membrane is soaked in 1M KOH solution at 80 ℃ for 500h, the ionic conductivity can be kept above 89%, and good chemical stability is shown.

Example 3

In this embodiment, taking a long-carbon-chain comb-shaped phenolphthalein based polyaryletherketone nitrile anion-exchange membrane containing 12 carbon atoms (the proportion of ketone segments is 40%) as an example, the structural formula is as follows:

wherein R is H or

The preparation method comprises the following steps:

1) synthesis of phenolphthalein-based polymer: 4,4' -dichlorobenzophenone (4mmol, 1.004g), 3, 5-dichlorobenzonitrile (6mmol, 1.032g), o-tolylphenolphthalein (10mmol, 3.465g), 3.452g (25mmol) anhydrous potassium carbonate and 10mL of toluene are dissolved in 30mL of N, N-dimethylacetamide, the mixture is reacted for 4h at 145 ℃ under the protection of nitrogen, then heated to 170 ℃ for reaction for 20h, and after cooling, the mixture is precipitated with 400mL of methanol aqueous solution (the volume ratio of methanol to water is 1:1), filtered, washed and dried to obtain the polyaryletherketonitrile polymer.

2) Synthesis of bromomethylated polymers: 1g (2.1mmol) of the polymer is dissolved in 30mL1,1,2, 2-tetrachloroethane, then 0.752g (4.2mmol) of N-bromosuccinimide and 0.0782g (0.32mmol) of benzoyl peroxide are added, the mixture is reacted for 5 hours at 85 ℃, and after cooling, the bromomethylated polymer is obtained by precipitation with methanol, filtration, washing and drying.

3) Preparation of anion exchange membrane: dissolving 1g of bromomethylated polymer in 30mL of DMSO, slowly adding 0.717g (3.03mmol) of 1-dodecyl imidazole containing a flexible long carbon chain as an imidazole functionalized reagent, reacting at 45 ℃ for 36h, finally coating the casting solution on a glass plate, heating to volatilize the solvent to obtain a solid membrane, soaking the solid membrane in 0.1mol/L potassium hydroxide alkali liquor, reacting for 48h, and fully washing with deionized water to obtain the pectinate phenolphthalein polyaryletherketone nitrile anion exchange membrane.

4) And (3) testing results: the prepared anion exchange membrane forms a remarkable hydrophilic/hydrophobic micro-phase separation structure and developed OH^-An ion transport channel. Theoretical value of ion exchange capacity of 2.04mmol g^-1The test value was 1.76mmol g^-1. The water content of the film at 30 deg.C and 80 deg.C is 23.8% and 32.5%, and the film is soluble at 30 deg.C and 80 deg.CThe swelling was 6.5% and 8.8%. The ionic conductivity of the membrane at 30 ℃ and 80 ℃ is 39.2mS cm^-1And 81.7 mS. cm^-1. The resulting film was tested for a thermal decomposition temperature above 206 c, indicating that the film had good thermal stability. The membrane is soaked in 1M KOH solution at 80 ℃ for 500h, the ionic conductivity can be kept over 92 percent, and good chemical stability is shown.

The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents.

Claims

1. A phenolphthalein-based anion-exchange membrane containing comb-shaped side chains is characterized in that: the molecular structural formula is as follows:

wherein x is 0 to 1 and at least one R is

One of (1);

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

2. the preparation method of the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 1, which is characterized in that: the method comprises the following steps:

1) synthesis of phenolphthalein-based polymer: 1 part of o-tolylphenolphthalein and x parts of a solvent containing Ar₁Dihalo monomer of structure and 1-x parts of Ar₂Under the protection of nitrogen, anhydrous potassium carbonate with a molar weight 2.5-3 times that of o-tolylphenolphthalein and the presence of toluene, dissolving a dihalogen monomer with a structure in a polar aprotic solvent, reacting at 135-145 ℃ for 3-5 h, heating to 150-170 ℃ for 16-24 h, stopping the reaction, cooling to room temperature, precipitating with an alcohol-water solution, filtering, washing and drying to obtain a phenolphthalein-based polymer;

2) synthesis of brominated polymer: dissolving the phenolphthalein-based 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 imidazole functional reagent with an R structure, and reacting at 40-50 ℃ for 24-48 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 immersing the solid film into alkali liquor for 48-72 h for ion exchange, and fully washing with water to obtain the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain.

3. The method for preparing the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 2, wherein: said has Ar₁The dihalogen monomer with the structure comprises at least one of 4,4' -dichlorodiphenyl sulfone, 4' -dichlorobenzophenone, 4' -dichlorodiphenylmethane, 4' -dichlorobiphenyl, 3' -dichlorobiphenyl or 3, 5-dichlorobenzonitrile.

4. The method for preparing the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 2, wherein: said has Ar₂The dihalogen monomer with the structure comprises at least one of 4,4' -dichlorodiphenyl sulfone, 4' -dichlorobenzophenone, 4' -dichlorodiphenylmethane, 4' -dichlorobiphenyl, 3' -dichlorobiphenyl or 3, 5-dichlorobenzonitrile.

5. The method for preparing the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 2, wherein: the polar aprotic solvent includes at least one of dimethyl sulfoxide, N-dimethylacetamide, N-dimethylformamide, or N-methylpyrrolidone.

6. The method for preparing the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 2, wherein: in the step 2), the molar ratio of the phenolphthalein-based polymer to the N-bromosuccinimide to the initiator is 1: (2-5): (0.1-0.25).

7. The method for preparing the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 2, wherein: the initiator comprises at least one of benzoyl peroxide or azobisisobutyronitrile.

8. The method for preparing the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 2, wherein: the imidazole functionalizing agent comprises at least one of 1-pentylimidazole, 1-octylimidazole, 1-dodecylimidazole, or 1-decyl-2-methylimidazole.

9. The method for preparing the phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 2, wherein: 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 phenolphthalein-based anion-exchange membrane containing the comb-shaped side chain as claimed in claim 2, wherein: the aqueous alcohol solution comprises an aqueous methanol solution; the substrate comprises a glass plate or a polytetrafluoroethylene plate.