A method for preparing a brominated polyether ether ketone anion exchange membrane

Abstract

This invention first provides a method for preparing a brominated polyether ether ketone (PEEK) anion exchange membrane. The molar ratio of the brominated PEEK methyl group to the multi-cationic side chains is 1:1. A fluorene-containing PEEK is selected as the main chain, which possesses excellent chemical and thermal stability. After bromination, multi-cationic side chains are grafted to prepare a high-performance anion exchange membrane. Firstly, the multi-cationic side chains effectively improve the ion exchange capacity and hydroxide ion conduction efficiency. Secondly, the highly rigid fluorene structure and conjugated system in the polymer main chain enhance the mechanical and chemical stability of the anion exchange membrane. Its steric hindrance effect inhibits membrane swelling and reduces hydroxide ion erosion, thus effectively ensuring the membrane's dimensional stability and alkali resistance. Finally, the synergistic effect of rigidity and flexibility between the main chain and side chains provides a strong driving force for ion self-aggregation, contributing to the formation of a microphase separation structure, while the ordered ion channels achieve a good balance between membrane mechanical strength and electrochemical performance. Experimental results show that the proton conductivity of the anion exchange membrane of the present invention is 0.082 S cm⁻¹ at 80 °C. ‑1 -0.122 S cm ‑1 The thickness of the anion exchange membrane is 20-50 μm.

Description

Technical Field

[0001] This invention belongs to the fields of anion exchange membrane fuel cells and polymer chemistry, and specifically describes a method for preparing a brominated polyether ether ketone anion exchange membrane. Background Technology

[0002] Anion exchange membranes (AEMs) are the core components of anion exchange membrane fuel cells (AEMFCs), playing a crucial role in isolating hydrogen and oxygen and transporting hydroxide ions. Their performance directly affects the fuel cell's output efficiency and long-term stability. Currently, the core challenge facing anion exchange membranes is balancing ionic conductivity and dimensional stability. Increasing the ion exchange capacity (IEC) to enhance ionic conductivity significantly exacerbates membrane swelling, leading to a decline in mechanical properties. Pursuing structural stability often comes at the expense of ion transport efficiency.

[0003] To achieve high ionic conductivity and good dimensional stability in anion exchange membranes, polyetheretherketone (PEEK), with its excellent chemical stability, thermal stability, and mechanical strength, was selected as the main chain. Its rigid main chain structure can suppress excessive swelling of the membrane through steric hindrance. Grafting cationic side chains with different structures onto the brominated PEEK main chain preserves the structural stability of the main chain while enhancing ion conductivity through multiple cationic sites, achieving an optimized balance between high conductivity and low swelling rate. This provides a new pathway for the preparation of high-performance anion exchange membranes. Summary of the Invention

[0004] To address the technical shortcomings of existing anion exchange membranes that struggle to balance ionic conductivity and dimensional stability, this invention provides a method for preparing a brominated polyether ether ketone (Br-PEEK) anion exchange membrane, achieving performance optimization through precise control of the molecular structure. This anion exchange membrane is composed of brominated polyether ether ketone grafted with multiple cationic side chains. The cationic side chains include monocations (trimethylamine TMA, 1-methylimidazolium Im), dications (6-dimethylhexylaminotrimethylammonium iodide Bc), and trications (N,N-dimethyl-6-{dimethyl[6-(trimethylammonium)hexyl]amino}hexylammonium diiodide Tc), which combine with brominated polyether ether ketone (Br-PEEK) through a grafting reaction to form a membrane material exhibiting both high ionic conductivity and high stability.

[0005] This invention is achieved through the following technical solution: This invention provides a method for preparing a brominated polyether ether ketone anion exchange membrane, which is formed by grafting brominated polyether ether ketone and multi-cationic side chains, wherein the molar ratio of brominated polyether ether ketone to multi-cationic side chains is 1:1.1-1.3.

[0006] In the above scheme, the thickness of the anion exchange membrane is 20-50 μm.

[0007] This invention also provides a method for preparing a brominated polyether ether ketone anion exchange membrane, comprising the following steps: Step 1: Synthesis of brominated polyether ether ketone Step 2: Synthesis of multi-cationic side chains Step 3: The multi-cationic side links are grafted onto brominated polyether ether ketone to obtain the casting solution. Step 4: Lay the casting solution obtained in Step 3 to obtain a brominated polyether ether ketone anion exchange membrane.

[0008] The brominated polyether ether ketone is prepared as follows: I. Preparation of Polyetheretherketone (PEEK) Under a nitrogen atmosphere, a mol of trimethylhydroquinone (TMHQ), b mol of 4,4-difluorobenzophenone (DFBP), and c mol of bisphenol monomer were added sequentially to a three-necked flask, where a:c = 3:1 and b = a + c. Then, measured amounts of solvent, dehydrating agent, and salt-forming agent were added to the flask. Reflux and mechanical stirring were initiated, and the temperature was gradually increased to 120-140 °C. The dehydrating agent was released after reflux for 4-5 hours. The temperature was then raised to 170-180 °C, and the reaction continued for 3-5 hours until the system became viscous. The viscous reaction solution was discharged into deionized water, repeatedly rinsed with boiling water to remove impurities, and dried to obtain polyetheretherketone (PEEK). II. Preparation of Brominated Polyether Ether Ketone (Br-PEEK) Under nitrogen protection and in the dark, d mol of polyetheretherketone (PEEK) was added to a three-necked flask, dissolved in a suitable amount of tetrachloroethane, and heated to 60-80 °C until completely dissolved. e mol of N-bromosuccinimide (NBS) and a suitable amount of benzoyl peroxide (BPO) initiator were added sequentially, and the mixture was heated to 80-100 °C for 4-6 hours. The ratio of d:e was 1:1.8-2.4. After the reaction was complete, the mixture was cooled to room temperature, repeatedly washed with solvent to remove impurities, and dried to obtain a pale yellow flocculent brominated polyetheretherketone (Br-PEEK).

[0009] Preferably, the bisphenol monomer is hydroquinone, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, 2,2-diallylbisphenol A, 4,4-(1-phenylethyl)bisphenol, tetramethylbiphenyl, allyl, bisphenol S, or 9,9-bis(4-hydroxyphenyl)fluorene. The solvent is preferably N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, anhydrous ethanol, tetrahydrofuran, or dimethyl sulfoxide; the salt-forming agent is anhydrous potassium carbonate; and the dehydrating agent is toluene, benzene, xylene, or petroleum ether.

[0010] The preparation method of the aforementioned multi-cationic side chain is as follows: I. Preparation of 6-dimethylhexylaminotrimethylammonium iodide dication (Bc) Add f mol of N,N,N',N'-tetramethyl-1,6-hexanediamine to a single-necked flask, followed by 50-70 mL of solvent to form a homogeneous mixture. Then, slowly add g mol of iodomethane, and quickly protect the mixture from light using a black light-blocking bag (f:g = 1:2). After reacting at room temperature for 4-8 hours, a white powdery solid is observed in the flask. Collect the solid product by vacuum filtration, wash three times with solvent, and finally air-dry in a fume hood for 24 hours to obtain the target dication product. II. Preparation of N,N-dimethyl-6-{dimethyl[6-(trimethylammonium)hexyl]amino}hexylammonium diiodide trication (Tc) Step 1: Add h mmol of 1,6-diiodohexane to a three-necked flask. Then add an appropriate amount of solvent II to dissolve it. Slowly add i mmol of trimethylamine and an appropriate amount of solvent II to the three-necked flask through a constant-pressure dropping funnel, where h:i = 5:1. After the addition is completed within 20-35 minutes, allow the reaction to proceed at room temperature for 20-24 hours. After the reaction is complete, the solution changes from clear to turbid. Wash the mixture, filter it, and finally place it in a vacuum oven. Step 2: Add j mmol of N,N,N',N'-tetramethyl-1,6-hexanediamine and an appropriate amount of solvent II to a three-necked flask. Then, slowly add k mmol of the mixture of 1-iodo-6-(N,N,N-trimethyl)hexaneamine and an appropriate amount of solvent II through a constant-pressure dropping funnel, where j:k = 10:1. After the addition is completed within 1-1.5 hours, the reaction is carried out at room temperature for 4-6 hours. Then, freeze-dry the mixture using a freeze dryer. The resulting white solid is washed with solvent I, filtered, and then transferred to a vacuum oven for drying.

[0011] Preferably, solvent one is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, anhydrous ethanol, tetrahydrofuran, or dimethyl sulfoxide, and solvent two is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, anhydrous ethanol, tetrahydrofuran, or dimethyl sulfoxide.

[0012] The preparation of the casting solution by grafting multi-cationic side links to brominated polyether ether ketone. Add 0.3 g of brominated polyether ether ketone to a three-necked flask, add 10 mL of N-methylpyrrolidone, and stir until a yellow transparent solution is obtained. Add a cationic monomer (TMA, Im, Bc, or Tc), wherein the molar ratio of the cationic monomer to the bromomethyl group is 1:1, and react at 60 °C for 18 hours to obtain the casting solution.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves performance optimization through precise control of the molecular structure via a synergistic design of a rigid main chain and flexible multi-cationic side chains. Dicationic (6-dimethylhexylaminotrimethylammonium iodide Bc) and tricationic (N,N-dimethyl-6-{dimethyl[6-(trimethylammonium)hexyl]amino}hexylammonium diiodide Tc) side chains are synthesized and grafted onto brominated polyether ether ketone (Br-PEEK) to form a membrane material with both high ionic conductivity and high stability. The rigid structure and steric hindrance effect of the brominated polyether ether ketone effectively suppress membrane swelling. The multi-cationic side chains significantly enhance the ion exchange capacity. Experimental results show that the Tc-grafted membrane achieves an IEC of 2.139 mmol / g and a hydroxide ion conductivity of 0.122 S cm⁻¹ at 80 °C. -1 After soaking in an alkaline environment (1 M NaOH, 80 °C) for 480 hours, the conductivity retention rate reached 81.5%, demonstrating excellent chemical stability. Attached Figure Description

[0014] Figure 1 This is a graph showing the change in ion conductivity of the anion exchange membranes prepared in Examples 1, 2, 3 and 4 of this invention. Figure 2 This is a graph showing the change in thermal stability of the anion exchange membranes prepared in Examples 1, 2, 3 and 4 of this invention. Figure 3 This is a graph showing the change in mechanical properties of the anion exchange membranes prepared in Examples 1, 2, 3 and 4 of this invention. Specific implementation methods Example 1: A method for preparing a brominated polyether ether ketone anion exchange membrane, the specific steps of which are as follows: (1) Under a nitrogen atmosphere, 5 mmol of trimethylhydroquinone (TMHQ), 20 mmol of 4,4-difluorobenzophenone (DFBP), and 15 mmol of bisphenol monomer were added sequentially to a three-necked flask. Then, sulfolane solvent, toluene dehydrating agent, and anhydrous potassium carbonate salting agent were added to the flask. Reflux and mechanical stirring were started, and the temperature was gradually increased to 120-140 °C. The dehydrating agent was released after reflux for 4-5 hours. The temperature was raised to 170-180 °C and the reaction continued for 3-5 hours until the system became viscous. The viscous reaction solution was discharged into deionized water, repeatedly rinsed with boiling water to remove impurities, and dried to obtain polyetheretherketone. The bisphenol monomer is preferably hydroquinone, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, 2,2-diallylbisphenol A, 4,4-(1-phenylethyl)bisphenol, tetramethylbiphenyl, allyl, bisphenol S, or 9,9-bis(4-hydroxyphenyl)fluorene, more preferably 9,9-bis(4-hydroxyphenyl)fluorene. (2) Under nitrogen protection and in the dark, 4 mmol of polyetheretherketone was added to a three-necked flask, dissolved in 50 mL of tetrachloroethane, and heated to 60-80 °C until completely dissolved. Then, 8 mmol of N-bromosuccinimide (NBS) and an appropriate amount of benzoyl peroxide (BPO) initiator were added sequentially, and the mixture was heated to 80-100 °C for 4-6 hours. The ratio of d:e was 1:1.8-2.4. After the reaction, the mixture was cooled to room temperature, repeatedly washed with anhydrous ethanol to remove impurities, and dried to obtain a pale yellow flocculent brominated polyetheretherketone (Br-PEEK). (3) Take 0.3 g of brominated polyether ether ketone and add 10 mL of N-methylpyrrolidone. Stir until a yellow transparent solution is formed. Add 132 μL of trimethylamine, a monocationic monomer, wherein the molar ratio of the cationic monomer to the bromomethyl group is 1:1. React at 60 °C for 18 hours to obtain the casting solution. The preferred solvents include, but are not limited to, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or dichloromethane (DCM).

[0015] The casting solution obtained in step (3) was cast onto a clean 10cm × 10cm glass plate and dried in an 80℃ oven for 48 hours. After naturally cooling to room temperature, the membrane was removed in deionized water. After treatment with 2 mol / L sodium hydroxide for 24 hours, it was repeatedly rinsed in deionized water to remove residual alkali, thus obtaining a brominated polyether ether ketone anion exchange membrane. The conductivity of the obtained anion exchange membrane was tested at 80℃ and found to be 0.082 S cm⁻¹. -1 The film thickness is 25 μm, and its conductivity is 0.021 S cm⁻¹ when tested at 20 °C. -1 .

[0016] Example 2 (1) Under a nitrogen atmosphere, 5 mmol of trimethylhydroquinone (TMHQ), 20 mmol of 4,4-difluorobenzophenone (DFBP), and 15 mmol of bisphenol monomer were added sequentially to a three-necked flask. Then, sulfolane solvent, toluene dehydrating agent, and anhydrous potassium carbonate salting agent were added to the flask. Reflux and mechanical stirring were started, and the temperature was gradually increased to 120-140 °C. The dehydrating agent was released after reflux for 4-5 hours. The temperature was raised to 170-180 °C and the reaction continued for 3-5 hours until the system became viscous. The viscous reaction solution was discharged into deionized water, repeatedly rinsed with boiling water to remove impurities, and dried to obtain polyetheretherketone. The bisphenol monomer is preferably hydroquinone, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, 2,2-diallylbisphenol A, 4,4-(1-phenylethyl)bisphenol, tetramethylbiphenyl, allyl, bisphenol S, or 9,9-bis(4-hydroxyphenyl)fluorene, more preferably 9,9-bis(4-hydroxyphenyl)fluorene. (2) Under nitrogen protection and in the dark, 4 mmol of polyetheretherketone was added to a three-necked flask, dissolved in 50 mL of tetrachloroethane, and heated to 60-80 °C until completely dissolved. Then, 8 mmol of N-bromosuccinimide (NBS) and an appropriate amount of benzoyl peroxide (BPO) initiator were added sequentially, and the mixture was heated to 80-100 °C for 4-6 hours. The ratio of d:e was 1:1.8-2.4. After the reaction, the mixture was cooled to room temperature, repeatedly washed with anhydrous ethanol to remove impurities, and dried to obtain a pale yellow flocculent brominated polyetheretherketone (Br-PEEK). (3) Take 0.3 g of brominated polyether ether ketone and add it to a three-necked flask. Add 10 mL of N-methylpyrrolidone and stir until a yellow transparent solution is formed. Add 108 μL of 1-methylimidazole monocationic monomer, wherein the molar ratio of cationic monomer to bromomethyl is 1:1. React at 60 °C for 18 hours to obtain the casting solution. The preferred solvents include, but are not limited to, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and dichloromethane (DCM).

[0017] The casting solution obtained in step (3) was cast onto a clean 10cm × 10cm glass plate and dried in an 80℃ oven for 48 hours. After naturally cooling to room temperature, the membrane was removed in deionized water. After treatment with 2 mol / L sodium hydroxide for 24 hours, it was repeatedly rinsed in deionized water to remove residual alkali, thus obtaining a brominated polyether ether ketone anion exchange membrane. The obtained anion exchange membrane was tested at 80℃, and the conductivity of the membrane was 0.081 S cm⁻¹. -1The film thickness is 25 μm, and its conductivity is 0.030 S cm⁻¹ when tested at 20 °C. -1 .

[0018] Example 3 (1) Under a nitrogen atmosphere, 5 mmol of trimethylhydroquinone (TMHQ), 20 mmol of 4,4-difluorobenzophenone (DFBP), and 15 mmol of bisphenol monomer were added sequentially to a three-necked flask. Then, sulfolane solvent, toluene dehydrating agent, and anhydrous potassium carbonate salting agent were added to the flask. Reflux and mechanical stirring were started, and the temperature was gradually increased to 120-140 °C. The dehydrating agent was released after reflux for 4-5 hours. The temperature was raised to 170-180 °C and the reaction continued for 3-5 hours until the system became viscous. The viscous reaction solution was discharged into deionized water, repeatedly rinsed with boiling water to remove impurities, and dried to obtain polyetheretherketone. The bisphenol monomer is preferably hydroquinone, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, 2,2-diallylbisphenol A, 4,4-(1-phenylethyl)bisphenol, tetramethylbiphenyl, allyl, bisphenol S, or 9,9-bis(4-hydroxyphenyl)fluorene, more preferably 9,9-bis(4-hydroxyphenyl)fluorene. (2) Under nitrogen protection and in the dark, 4 mmol of polyetheretherketone was added to a three-necked flask, dissolved in 50 mL of tetrachloroethane, and heated to 60-80 °C until completely dissolved. Then, 8 mmol of N-bromosuccinimide (NBS) and an appropriate amount of benzoyl peroxide (BPO) initiator were added sequentially, and the mixture was heated to 80-100 °C for 4-6 hours. The ratio of d:e was 1:1.8-2.4. After the reaction, the mixture was cooled to room temperature, repeatedly washed with anhydrous ethanol to remove impurities, and dried to obtain a pale yellow flocculent brominated polyetheretherketone (Br-PEEK). (3) Add 0.05 mol of N,N,N',N'-tetramethyl-1,6-hexanediamine to a single-necked flask, followed by 60 mL of tetrahydrofuran to form a homogeneous mixture. Then, slowly add 0.65 mL of iodomethane and quickly protect the mixture from light using a black light-blocking bag. After reacting at room temperature for 4-8 hours, a white powdery solid was observed in the flask. The solid product was collected by vacuum filtration, washed three times with tetrahydrofuran, and finally air-dried in a fume hood for 24 hours to obtain the target dication product. (4) Take 0.3 g of brominated polyether ether ketone and add 10 mL of N-methylpyrrolidone. Stir until a yellow transparent solution is formed. Add 0.126 g of a dicationic monomer, wherein the molar ratio of the dicationic monomer to bromomethyl is 1:1. React at 60 °C for 18 hours to obtain a casting solution. The preferred solvents include, but are not limited to, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or dichloromethane (DCM).

[0019] The casting solution obtained in step (4) was cast onto a clean 10cm × 10cm glass plate and dried in an 80℃ oven for 48 hours. After naturally cooling to room temperature, the membrane was desorbed in deionized water. After treatment with 2 mol / L sodium hydroxide for 24 hours, it was repeatedly rinsed in deionized water to remove residual alkali, thus obtaining a brominated polyether ether ketone anion exchange membrane. The obtained anion exchange membrane was tested at 80℃, and the conductivity of the membrane was 0.102 S cm⁻¹. -1 The film thickness is 26 μm, and its conductivity is 0.034 S cm⁻¹ when tested at 20 °C. -1 .

[0020] Example 4 (1) Under a nitrogen atmosphere, 5 mmol of trimethylhydroquinone (TMHQ), 20 mmol of 4,4-difluorobenzophenone (DFBP), and 15 mmol of bisphenol monomer were added sequentially to a three-necked flask. Then, sulfolane solvent, toluene dehydrating agent, and anhydrous potassium carbonate salting agent were added to the flask. Reflux and mechanical stirring were started, and the temperature was gradually increased to 120-140 °C. The dehydrating agent was released after reflux for 4-5 hours. The temperature was raised to 170-180 °C and the reaction continued for 3-5 hours until the system became viscous. The viscous reaction solution was discharged into deionized water, repeatedly rinsed with boiling water to remove impurities, and dried to obtain polyetheretherketone. The bisphenol monomer is preferably hydroquinone, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, 2,2-diallylbisphenol A, 4,4-(1-phenylethyl)bisphenol, tetramethylbiphenyl, allyl, bisphenol S, or 9,9-bis(4-hydroxyphenyl)fluorene, more preferably 9,9-bis(4-hydroxyphenyl)fluorene. (2) Under nitrogen protection and in the dark, 4 mmol of polyetheretherketone was added to a three-necked flask, dissolved in 50 mL of tetrachloroethane, and heated to 60-80 °C until completely dissolved. Then, 8 mmol of N-bromosuccinimide (NBS) and an appropriate amount of benzoyl peroxide (BPO) initiator were added sequentially, and the mixture was heated to 80-100 °C for 4-6 hours. The ratio of d:e was 1:1.8-2.4. After the reaction, the mixture was cooled to room temperature, repeatedly washed with anhydrous ethanol to remove impurities, and dried to obtain a pale yellow flocculent brominated polyetheretherketone (Br-PEEK). (3) Add 50 mmol of 1,6-diiodohexane to a three-necked flask. Then add an appropriate amount of tetrahydrofuran to dissolve it. Slowly add a mixed solution of 10 mmol of trimethylamine and 10 mL of tetrahydrofuran dropwise to the three-necked flask through a constant pressure dropping funnel. After the addition is completed within 20-35 minutes, the reaction is allowed to proceed at room temperature for 20-24 hours. After the reaction is complete, the solution changes from clear to turbid. The mixture is washed, filtered, and finally placed in a vacuum oven. (4) Add 50 mmol of N,N,N',N'-tetramethyl-1,6-hexanediamine and 40 mL of dimethyl sulfoxide to a three-necked flask. Then, slowly add 5 mmol of a mixed solution of 1-iodo-6-(N,N,N-trimethyl)hexaneamine and 20 mL of dimethyl sulfoxide through a constant-pressure dropping funnel. After the addition is completed in 1-1.5 hours, the reaction is carried out at room temperature for 4-6 hours. Then, freeze-dry the mixture. The resulting white solid is washed with solvent, filtered, and then transferred to a vacuum oven to dry. (5) Take 0.3 g of brominated polyether ether ketone and add 10 mL of N-methylpyrrolidone. Stir until a yellow transparent solution is formed. Add 0.034 g of a dicationic monomer, wherein the molar ratio of the tricationic monomer to the bromomethyl group is 1:1. React at 60 °C for 18 hours to obtain the casting solution. The preferred solvents include, but are not limited to, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or dichloromethane (DCM).

[0021] The casting solution obtained in step (4) was cast onto a clean 10cm × 10cm glass plate and dried in an 80℃ oven for 48 hours. After naturally cooling to room temperature, the membrane was removed in deionized water. After treatment with 2 mol / L sodium hydroxide for 24 hours, it was repeatedly rinsed in deionized water to remove residual alkali, thus obtaining a brominated polyether ether ketone anion exchange membrane. The obtained anion exchange membrane was tested at 80℃, and the conductivity of the membrane was 0.122 S cm⁻¹. -1 The film thickness is 24 μm, and its conductivity is 0.045 S cm⁻¹ when tested at 20 °C.-1 .

[0022] Figure 1 This is a graph showing the ionic conductivity of the anion exchange membranes prepared in Examples 1, 2, 3, and 4 of this invention as a function of temperature. The anion exchange membrane prepared in Example 4 exhibits the highest ionic conductivity.

[0023] Figure 2 The figures show the thermogravimetric curves of the anion exchange membranes prepared in Examples 1, 2, 3, and 4 of this invention. Examples 1 and 2 exhibit two similar weight loss stages. The first stage begins at 210 °C, mainly due to the degradation of trimethylamine and imidazole cation functional groups on the polymer backbone; the weight loss occurring at temperatures above 490 °C is mainly attributed to the degradation of the polymer backbone. Examples 3 and 4 exhibit three similar weight loss stages: the first stage begins at 180 °C due to the partial breakage of quaternary ammonium cation groups on the long side chains; the second stage begins at around 320 °C, originating from the complete degradation of the side chain groups; and the third stage occurs at 560 °C, caused by the breakage of the polymer backbone.

[0024] Figure 3 The graphs show the mechanical properties of the anion exchange membranes prepared in Examples 1, 2, 3, and 4 of this invention. Example 4 has a tensile strength of 24.11 MPa and an elongation at break of 13.47%.

[0025] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a brominated polyether ether ketone anion exchange membrane, characterized in that, The anion exchange membrane is formed by grafting a brominated polyether ether ketone backbone with cationic side chains. The molar ratio of brominated polyether ether ketone to cationic side chains is 1:

1. The cationic side chains are selected from trimethylamine (TMA), 1-methylimidazole (Im), 6-dimethylhexylaminotrimethylammonium iodide (Bc), and N,N-dimethyl-6-{dimethyl[6-(trimethylammonium)hexyl]amino}hexylammonium diiodide (Tc).

2. The method for preparing a polyetheretherketone anion exchange membrane according to claim 1, characterized in that, The main chain is polyetheretherketone (PEEK), and its preparation method is as follows: Under a nitrogen protective atmosphere, a mol of trimethylhydroquinone (TMHQ), b mol of 4,4-difluorobenzophenone (DFBP), and c mol of bisphenol monomer are added sequentially to a three-necked flask, where a:c = 3:1 and b = a + c. Then, a measured amount of solvent, dehydrating agent, and salt-forming agent are added to the flask. Reflux and mechanical stirring are started, and the temperature is gradually increased to 120-140 °C. The dehydrating agent is released after reflux for 4-5 hours. The temperature is raised to 170-180 °C, and the reaction continues for 3-5 hours until the system becomes viscous. The viscous reaction solution is discharged into deionized water, repeatedly rinsed with boiling water to remove impurities, and dried to obtain the PEEK main chain.

3. The method for preparing a brominated polyether ether ketone anion exchange membrane according to claim 1, characterized in that, The main chain is brominated polyether ether ketone, and its preparation method is as follows: Under nitrogen protection and in the dark, d mol of the polyether ether ketone main chain is added to a three-necked flask, and an appropriate amount of tetrachloroethane is added to dissolve it. The temperature is raised to 60-80 °C until completely dissolved. e mol of N-bromosuccinimide (NBS) and an appropriate amount of benzoyl peroxide (BPO) initiator are added sequentially, and the temperature is raised to 80-100 °C for 4-6 hours. The ratio of d:e is 1:1.8-2.

4. After the reaction is complete, the mixture is cooled to room temperature, repeatedly washed with solvent to remove impurities, and dried to obtain a pale yellow flocculent brominated polyether ether ketone (Br-PEEK).

4. The method for preparing a polyetheretherketone anion exchange membrane according to claim 1, characterized in that, The brominated polyether ether ketone (PEEK) is prepared by means of a bisphenol monomer preferably hydroquinone, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, 2,2-diallylbisphenol A, 4,4-(1-phenylethyl)bisphenol, tetramethylbiphenyl, allyl, bisphenol S, or 9,9-bis(4-hydroxyphenyl)fluorene. The preferred solvents are N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, anhydrous ethanol, tetrahydrofuran, or dimethyl sulfoxide. The salting agent is anhydrous potassium carbonate, and the dehydrating agent is toluene, benzene, xylene, or petroleum ether.

5. The method for preparing a brominated polyether ether ketone anion exchange membrane according to claim 1, characterized in that, The side chain is a 6-dimethylhexylaminotrimethylammonium iodide dication (Bc) side chain, and its preparation method is as follows: f mol of N,N,N',N'-tetramethyl-1,6-hexanediamine was added to a single-necked flask, followed by 50-70 mL of solvent to form a homogeneous mixture. Then, g mol of iodomethane was slowly added dropwise, and the mixture was quickly protected from light using a black light-blocking bag, where f:g = 1:

2. After reacting at room temperature for 4-8 hours, a white powdery solid was observed in the flask. The solid product was collected by vacuum filtration, washed three times with solvent, and finally air-dried in a fume hood for 24 hours to obtain the target dication product.

6. The method for preparing a brominated polyether ether ketone anion exchange membrane according to claim 1, characterized in that, The side chain portion is an N,N-dimethyl-6-{dimethyl[6-(trimethylammonium)hexyl]amino}hexylammonium diiodide trication (Tc) trication side chain, and its preparation method is as follows: Step 1: Add h mmol of 1,6-diiodohexane to a three-necked flask. Then add an appropriate amount of solvent II to dissolve it. Slowly add i mmol of trimethylamine and an appropriate amount of solvent II solution dropwise to the three-necked flask through a constant pressure dropping funnel, where h:i = 5:

1. After the addition is completed within 20-35 minutes, allow the reaction to proceed at room temperature for 20-24 hours. After the reaction is complete, the solution changes from clear to turbid. Wash the mixture, filter it, and finally place it in a vacuum oven.

7. Step Two: Add j mmol of N,N,N',N'-tetramethyl-1,6-hexanediamine and an appropriate amount of solvent II to a three-necked flask. Then, slowly add k mmol of the mixture of 1-iodo-6-(N,N,N-trimethyl)hexaneamine and an appropriate amount of solvent II through a constant-pressure dropping funnel, where j:k = 10:

1. After the addition is completed within 1-1.5 hours, the reaction is carried out at room temperature for 4-6 hours. Then, freeze-dry the mixture using a freeze dryer. The resulting white solid is washed with solvent I, filtered, and then transferred to a vacuum oven for drying.

8. A method for preparing a brominated polyether ether ketone anion exchange membrane according to claims 5 and 6, characterized in that, The multi-cationic side chain is prepared by means of solvent one, which is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, anhydrous ethanol, tetrahydrofuran, or dimethyl sulfoxide; and solvent two is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, anhydrous ethanol, tetrahydrofuran, or dimethyl sulfoxide.

9. The method for preparing a brominated polyether ether ketone anion exchange membrane according to claim 1, characterized in that... The cationic side links are grafted onto the main chain of the brominated polyether ether ketone. The preparation method is as follows: 0.3 g of the brominated polyether ether ketone polymer is added to a three-necked flask, followed by 10 mL of N-methylpyrrolidone. The mixture is stirred until a yellow, transparent solution is formed. A cationic monomer (TMA, Im, Bc, or Tc) is added, wherein the molar ratio of the cationic monomer to the bromomethyl group is 1:

1. The mixture is reacted at 60 °C for 18 hours to obtain the casting solution.

10. The method for preparing a brominated polyether ether ketone anion exchange membrane according to claim 8, characterized in that, The specific steps for membrane laying in the above steps are as follows: the casting solution is cast onto a clean glass plate surface of 10cm×10cm, dried in an oven at 60-80℃ for 24-48 hours, deionized water is used for membrane removal, the membrane is soaked in sodium hydroxide for 24-48 hours, and finally repeatedly washed with deionized water until there is no residual alkali on the membrane surface, thus obtaining the brominated polyether ether ketone anion exchange membrane for fuel cells.

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