Aromatic proton exchange membrane with regional disulfonic acid side chain structure and preparation method of aromatic proton exchange membrane

Abstract

The invention provides an aromatic proton exchange membrane with a regional disulfonic acid side chain structure and a preparation method of the aromatic proton exchange membrane, and belongs to the technical field of proton exchange membranes. The preparation method comprises the following steps: selecting p-terphenyl, 2, 2, 2-trifluoroacetophenone and 2, 3, 4, 5, 6-pentafluorobenzaldehyde as monomers, obtaining an aromatic polymer by virtue of a super acid polymerization method, then adding 2-naphthol-6, 8-dipotassium disulfonate hydrate, and successfully realizing positioning controllable sulfonation of side chain phenyl of the polymer by virtue of a double-solvent method. The main chain of the polymer is an ether-free aromatic skeleton, so that good chemical stability is guaranteed from the source; a flexible regional disulfonic acid side chain is beneficial to induction and formation of a continuous proton transmission channel, so that excellent proton conductivity is realized; meanwhile, due to the phenyl stacking effect of a side chain naphthyl structure, the proton membrane has excellent dimensional stability; the invention provides a solution aiming at the contradiction that the proton conductivity and the dimensional stability of a common aromatic proton exchange membrane are difficult to be compatible.

Description

Technical Field

[0001] The invention belongs to the technical field of proton exchange membranes, and particularly relates to an aromatic polymer with a regional disulfonic acid side chain structure and a preparation method thereof. Background Art

[0002] Against the backdrop of global warming and environmental crises, large-scale decarbonization of the energy and industrial systems is imperative. Hydrogen, a diverse, low-carbon, and widely applicable clean energy source, will play a key role in transforming the energy system and decarbonizing modern industrial systems, providing crucial support. Hydrogen energy development and utilization technologies, particularly fuel cell technology, are gaining widespread attention.

[0003] Proton exchange membranes are core components of fuel cells, effectively isolating the anode and cathode while transferring protons. They also serve as catalyst supports, forming the membrane electrode, the primary site for electrochemical reactions. They play a central role in both water electrolysis and fuel cells, and hold significant practical significance and broad prospects for the development of hydrogen energy. Currently, the most commercialized fuel cell membrane is a perfluorosulfonic acid membrane, represented by Nafion. Perfluorosulfonic acid membranes generally offer excellent conductivity and reliable stability, but their high cost and demanding production conditions have limited their large-scale application. Consequently, numerous researchers are dedicated to developing technologies for the controllable preparation of low-cost aromatic proton exchange membranes.

[0004] The synthesis of aromatic proton exchange membranes can be primarily categorized into two approaches. The first involves using existing commercial aromatic polymers as raw materials and introducing conductive sulfonic acid groups via post-sulfonation. While this method is relatively simple, the polymer backbone often contains numerous ether bonds or heteroatoms, which can easily absorb water and swell, resulting in poor chemical and dimensional stability. Examples include sulfonated polyetheretherketone (PEEK), polyarylethersulfone (PES), and polyimide (PI). The second approach involves synthesizing aromatic polymers for use in proton exchange membranes. Sulfonation can be performed either during the monomer stage or after polymerization. However, because sulfonated monomers are generally difficult to polymerize, post-sulfonation is often employed, such as with sulfonated polyarylalkyl groups. During post-sulfonation, the polymer's polarity changes due to changes in its chemical structure before and after sulfonation. Consequently, the solubility properties of the polymer before and after sulfonation often differ, making sulfonation difficult and the degree of sulfonation uncontrollable, leading to poor conductivity. Therefore, developing novel proton exchange membranes with both excellent conductivity and stability is of great practical significance for the large-scale deployment of hydrogen energy. Summary of the Invention

[0005] The present invention aims to provide an aromatic proton exchange membrane with a regional disulfonic acid side chain structure and a preparation method thereof. In this method, an ether-free aromatic polymer is placed in a dual solvent system consisting of a good solvent before polymer sulfonation and a good solvent after polymer sulfonation to carry out a sulfonation reaction, thereby solving the problems of difficult sulfonation and uncontrollable sulfonation degree. The prepared aromatic proton exchange membrane with a regional disulfonic acid side chain structure has good conductivity and stability.

[0006] To achieve the above object, the present invention provides the following technical solutions: One of the technical solutions of the present invention is to provide an aromatic polymer of a terphenyl-pentafluorobenzaldehyde copolymer grafted with naphthol disulfonic acid, the chemical structure of which is shown below:

[0007] Wherein, n is selected from 0.5 to 0.9.

[0008] The aromatic proton exchange membrane with a regional disulfonic acid structure is obtained by first polymerizing terphenyl, 2,2,2-trifluoroacetophenone and 2,3,4,5,6-pentafluorobenzaldehyde through a dehydration condensation reaction to obtain an ether-free aromatic polymer; then placing the ether-free aromatic polymer in a dual solvent system consisting of a good solvent before polymer sulfonation and a good solvent after polymer sulfonation to complete the positional controllable sulfonation of the side chain phenyl group.

[0009] The second technical solution of the present invention is to provide a method for preparing the above-mentioned polymer, comprising the following steps: (1) Dissolve p-terphenyl, 2,2,2-trifluoroacetophenone and 2,3,4,5,6-pentafluorobenzaldehyde in a polymerization solvent, add trifluoromethanesulfonic acid in an ice bath and stir evenly; after the addition of trifluoromethanesulfonic acid, heat the reaction solution to 15-30 o C, carrying out polymerization reaction, after a certain period of time, the reaction is completed, the reaction solution is poured into a poor solvent for the polymer, filtered, purified, and dried to obtain an ether-free aromatic polymer; (2) dissolving the ether-free aromatic polymer in a good solvent before the polymer is sulfonated to obtain a polymer solution, and controlling the solid content of the polymer solution to be 3-8 wt %; then sequentially adding a base and 2-naphthol-6,8-disulfonic acid dipotassium hydrate to the polymer solution, and stirring evenly; then sequentially adding the good solvent after the polymer is sulfonated and cyclohexane, heating to a certain temperature range to carry out polymerization reaction, terminating the reaction after a period of reaction, drying, and purifying to obtain an aromatic polymer with a regional disulfonic acid side chain structure; (3) The aromatic polymer with a regional disulfonic acid side chain structure is dissolved in a good solvent after polymer sulfonation, and the solid content of the solution is controlled to 5wt%; after filtering and vacuuming, a casting solution is obtained, and then the casting solution is cast on a horizontal glass plate, and the solvent is dried to form a membrane; then the membrane is immersed in a 1M dilute sulfuric acid solution for 12 to 36 hours, and then the membrane surface is washed with pure water to remove free hydrogen ions to obtain an aromatic proton exchange membrane with a regional disulfonic acid side chain structure.

[0010] Furthermore, in step (1), the polymerization reaction solvent is one of dichloromethane and chloroform; the polymer poor solvent is one or more of methanol, ethanol, water, and ethyl acetate; in step (2), the good solvent before the polymer is sulfonated is one of N,N-dimethylacetamide and N-methylpyrrolidone; the base is one of potassium carbonate, sodium hydroxide, potassium hydroxide, sodium hydride, and sodium carbonate; and the good solvent after the polymer is sulfonated is one of dimethyl sulfoxide and N,N-dimethylformamide.

[0011] Furthermore, in step (1), the molar ratio of p-terphenyl to trifluoromethanesulfonic acid is 1:3~10; the polymerization reaction time is 1~9h; in step (2), the molar amount of the ether-free aromatic polymer is based on the molar amount of pentafluorobenzaldehyde monomer in the polymer, and the molar ratio of the ether-free aromatic polymer, the base, and the 2-naphthol-6,8-disulfonic acid dipotassium hydrate is 1:1.3~2:1.5~2; the volume ratio of the good solvent before the polymer sulfonation to the good solvent after the polymer sulfonation is 1:0.8~1.2; the volume ratio of the good solvent after the polymer sulfonation to cyclohexane is 1:0.4~0.6; the polymerization reaction temperature range is 110~150 o C; time is 12~24h.

[0012] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) The aromatic proton exchange membrane with a regional disulfonic acid side chain structure provided by the present invention has a polymer structure of an aromatic polymer main chain plus a naphthalene ring disulfonic acid side chain structure. The side chain naphthalene ring structure has a strong phenyl stacking effect, which makes the polymer chains stack more tightly, the overall water absorption and swelling are small, and it exhibits higher dimensional stability, thereby achieving a balance between conductivity and dimensional stability of the proton membrane.

[0013] (2) The method of the present invention places the ether-free aromatic polymer in a dual solvent system consisting of a good solvent before the polymer is sulfonated and a good solvent after the polymer is sulfonated to carry out a sulfonation reaction, thereby solving the problem of difficulty in sulfonation and uncontrollable sulfonation degree caused by changes in solubility properties due to changes in polarity before and after the polymer is sulfonated.

[0014] (3) The method of the present invention successfully introduces a regional disulfonic acid side chain structure by grafting dipotassium 2-naphthol-6,8-disulfonic acid onto the polymer main chain. The presence of the regional disulfonic acid side chain structure achieves the enrichment of sulfonic acid groups to a certain extent, and exhibits more superior proton conduction performance than traditional monosulfonic acid side chains, effectively improving the conductivity of the proton exchange membrane.

[0015] (4) The method of the present invention uses p-terphenyl, pentafluorobenzaldehyde and trifluoroacetophenone as polymerization monomers, and realizes polymerization by superacid polymerization method to construct a polymer with an ether-free main chain and a side chain mainly composed of aromatic naphthalene rings, which has good chemical stability. Experiments show that the proton membrane remains intact after the Fenton test and the mass retention rate is above 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a synthetic route for the aromatic polymer with regional disulfonic acid side chains in Example 1 of the present invention; Figure 2 The NMR spectra of the ether-free aromatic polymer and the aromatic polymer with regional disulfonic acid side chains in Example 1 of the present invention are shown; Figure 3 Thermogravimetric spectra of the aromatic polymer with a regional disulfonic acid side chain structure before and after sulfonation in Example 1 of the present invention; Figure 4 Graph showing the conductivity variation with temperature of the aromatic proton exchange membranes with regional disulfonic acid side chain structures in Examples 1 to 5 of the present invention and the aromatic proton exchange membrane without regional disulfonic acid side chain structures in Comparative Example 1; Figure 5 Graph showing the water absorption rate of the aromatic proton exchange membranes with regional disulfonic acid side chain structures in Examples 1 to 5 of the present invention and the aromatic proton exchange membrane without regional disulfonic acid side chain structures in Comparative Example 1 as a function of temperature; Figure 6 The figure shows the trend of the swelling ratio of the aromatic proton exchange membranes with regional disulfonic acid side chain structures in Examples 1 to 5 of the present invention and the aromatic proton exchange membrane without regional disulfonic acid side chain structures in Comparative Example 1 as a function of temperature. DETAILED DESCRIPTION

[0017] The following describes the implementation methods of the present invention in conjunction with specific implementation cases, but the implementation methods of the present invention are not limited to the specific implementation plans described below. It should be understood that researchers in the research field to which the present invention belongs, without paying any creative work, obtain other embodiments similar to the present invention, which all fall within the scope of protection of the present invention.

[0018] It should be understood that unless otherwise defined, the technical and related scientific terms used in the present invention have the same meaning as commonly understood by researchers in the research field to which the present invention belongs. Example 1

[0019] This embodiment provides a method for preparing an aromatic proton exchange membrane with a regional disulfonic acid side chain structure, which specifically includes the following steps: (1) Synthesis of ether-free aromatic polymers: 10 mmol of p-terphenyl, 5 mmol of 2,2,2-trifluoroacetophenone and 5 mmol of 2,3,4,5,6-pentafluorobenzaldehyde were added to 10 mL of dichloromethane (CH2Cl2) and stirred to mix thoroughly. The reaction solution was then placed in an ice bath to cool for 15 min. After cooling, 8 mL of trifluoromethanesulfonic acid (TFSA) was slowly added to the reaction solution. The reaction solution was then placed at 30°C for 1 h. The reaction solution was then poured into methanol to form a white fibrous polymer precipitate. The precipitate was filtered and dried. The precipitate was then dissolved with N,N-dimethylacetamide. The polymer solution was then poured into methanol for precipitation to complete a purification step. After purification three times, the polymer solid was placed in an oven for drying to obtain a skeleton ether-free aromatic polymer.

[0020] (2) Synthesis of aromatic polymer with regional disulfonic acid side chain structure: 1 g of the ether-free aromatic polymer obtained above was added with 20 mL of N,N-dimethylacetamide at 60 o C heating conditions were used to dissolve the polymer solid to form a polymer solution; then 0.26 g of potassium carbonate was added to the reaction system and stirred evenly, and then 0.72 g of 2-naphthol-6,8-disulfonic acid dipotassium hydrate was added and stirred evenly; after stirring for 30 minutes, 20 mL of dimethyl sulfoxide was added to the system and stirred; 10 mL of cyclohexane was added as a dehydrating agent, and then the reaction system was heated to 110 o C. After continuous stirring for 24 hours, the reaction solution was poured into a tray and placed in an oven to dry to obtain a solid. The polymer solid was then washed with pure water and water-soluble impurities were filtered out. The washed polymer solid was then placed in an oven to dry and then dissolved in dimethyl sulfoxide to obtain a polymer solution. The polymer solution was poured into methanol for precipitation. This was repeated three times to complete purification to obtain an aromatic polymer with a regional disulfonic acid side chain structure.

[0021] (3) Preparation of aromatic proton exchange membrane with regional disulfonic acid side chain structure: 1g of aromatic polymer with regional disulfonic acid side chain structure was taken and heated at 60 o C, 20 mL of dimethyl sulfoxide was used to dissolve the polymer solution, which was then filtered with a sand core funnel to remove insoluble impurities to obtain a film injection solution; the film injection solution was then poured onto a flat glass plate and heated for 60 min. oC conditions to evaporate the solvent for 12 hours, then place the glass plate in pure water for 30 minutes, at which time the membrane is completely separated from the glass plate, then take out the membrane and soak it in a 1 mol / L dilute sulfuric acid solution for 24 hours, then take out the membrane and wash the free acid on the membrane surface with deionized water to obtain an aromatic proton exchange membrane with a regional disulfonic acid side chain structure.

[0022] The structural formula of the proton exchange membrane obtained in this embodiment is:

[0023] The aromatic proton exchange membrane with a regional disulfonic acid side chain structure obtained in this example was cut into 1×4 cm strips and placed in a conductivity test fixture. Its conductivity was tested using the four-probe method. The mass, length, width, and thickness of the proton exchange membrane when dry were measured, and the mass, length, width, and thickness after absorbing water at different temperatures were measured. The water absorption rate and swelling ratio of the proton exchange membrane were obtained by comparing them with the corresponding data when dry. At the same time, the proton exchange membrane was placed at 60 o C Fenton reagent for 1 hour to test its oxidation stability. The test found that the conductivity of the proton exchange membrane obtained in this embodiment was 25 o C is 0.068Scm -1 , in 80 o Under C conditions, the water absorption rate was 31.5%, the corresponding swelling ratio was only 14.2%, and the mass retention rate after Fenton test was 99.7%. Example 2

[0024] This embodiment provides a method for preparing an aromatic proton exchange membrane with a regional disulfonic acid side chain structure, which specifically includes the following steps: (1) Synthesis of ether-free aromatic polymer: 10 mmol of p-terphenyl, 4 mmol of 2,2,2-trifluoroacetophenone, and 6 mmol of 2,3,4,5,6-pentafluorobenzaldehyde were added to 10 mL of dichloromethane and stirred to mix thoroughly. The reaction solution was then placed in an ice bath to cool for 15 min. After cooling, 2.7 mL of trifluoromethanesulfonic acid (TFSA) was slowly added to the reaction solution. The reaction solution was then placed at 30°C for 9 h. The reaction solution was then poured into ethanol to form a white fibrous polymer precipitate. The remaining experimental steps were the same as step (1) of Example 1.

[0025] (2) Synthesis of aromatic polymer with regional disulfonic acid side chain structure: 1 g of the skeleton-free ether aromatic polymer obtained above was added with 20 mL of N,N-dimethylacetamide at 60 oC heating conditions were used to dissolve the polymer solid to form a polymer solution; then 0.078g of sodium hydroxide was added to the reaction solution and stirred evenly, followed by 0.74g of 2-naphthol-6,8-disulfonic acid dipotassium hydrate and stirring evenly. After stirring for 30 minutes, 20mL of N,N-dimethylformamide was added to the system and stirred; 10mL of cyclohexane was added as a dehydrating agent, and then the reaction system was heated to 130 o C. After continuous stirring for 19 h, the reaction solution was poured into a tray and placed in an oven to dry to obtain a solid. The remaining experimental steps were the same as step (2) of Example 1.

[0026] (3) Preparation of aromatic proton exchange membrane with regional disulfonic acid side chain structure: The experimental steps are the same as step (3) of Example 1.

[0027] The structural formula of the proton exchange membrane obtained in this embodiment is:

[0028] The proton exchange membrane obtained in this embodiment was tested, and the relevant steps were the same as in Example 1. The data obtained were that the proton exchange membrane 25 o The conductivity is 0.078Scm at C -1 , in 80 o The water absorption rate under C conditions was 33.9%, the corresponding swelling ratio was 16.1%, and the mass retention rate after Fenton test was 99.3%. Example 3

[0029] This embodiment provides a method for preparing an aromatic proton exchange membrane with a regional disulfonic acid side chain structure, which specifically includes the following steps: (1) Synthesis of ether-free aromatic polymer: 10 mmol of p-terphenyl, 3 mmol of 2,2,2-trifluoroacetophenone, and 7 mmol of 2,3,4,5,6-pentafluorobenzaldehyde were added to 10 mL of dichloromethane and stirred thoroughly. The reaction solution was then placed in an ice bath to cool for 15 min. After cooling, 8.8 mL of trifluoromethanesulfonic acid (TFSA) was slowly added to the reaction solution. The reaction solution was then placed at 30°C for 1 h. The reaction solution was then poured into water to form a white fibrous polymer precipitate. The remaining experimental steps were the same as step (1) of Example 1.

[0030] (2) Synthesis of aromatic polymer with regional disulfonic acid side chain structure: 1 g of the skeleton-free ether aromatic polymer obtained above was added with 20 mL of N-methylpyrrolidone at 60 oC heating conditions were used to dissolve the polymer solid to form a polymer solution; then 0.2 g of potassium hydroxide was added to the reaction solution and stirred evenly, and then 1.33 g of 2-naphthol-6,8-disulfonic acid dipotassium hydrate was added and stirred evenly. After stirring for 30 minutes, 16 mL of dimethyl sulfoxide was added to the system and stirred; 6.4 mL of cyclohexane was added as a dehydrating agent, and then the reaction system was heated to 150 o C, and continued stirring for 12 h. The remaining experimental steps were the same as step (2) of Example 1.

[0031] (3) Preparation of aromatic proton exchange membrane with regional disulfonic acid side chain structure: The experimental steps are the same as step (3) of Example 1.

[0032] The structural formula of the proton exchange membrane obtained in this embodiment is:

[0033] The proton exchange membrane obtained in this embodiment was tested, and the relevant steps were the same as in Example 1. The data obtained were that the proton exchange membrane 25 o The conductivity is 0.086Scm at C -1 , in 80 o The water absorption rate under C conditions was 42.4%, the corresponding swelling ratio was 15.5%, and the mass retention rate after Fenton test was 99.4%. Example 4

[0034] This embodiment provides a method for preparing an aromatic proton exchange membrane with a regional disulfonic acid side chain structure, which specifically includes the following steps: (1) Synthesis of ether-free aromatic polymer: 10 mmol of p-terphenyl, 2 mmol of 2,2,2-trifluoroacetophenone, and 8 mmol of 2,3,4,5,6-pentafluorobenzaldehyde were added to 10 mL of dichloromethane and stirred thoroughly. The reaction solution was then placed in an ice bath to cool for 15 min. After cooling, 4.4 mL of trifluoromethanesulfonic acid (TFSA) was slowly added to the reaction solution. The reaction solution was then placed at 30°C for 5 h. The reaction solution was then poured into ethyl acetate to form a white fibrous polymer precipitate. The remaining experimental steps were the same as those in step (1) of Example 1.

[0035] (2) Synthesis of aromatic polymer with regional disulfonic acid side chain structure: 1 g of the skeleton-free ether aromatic polymer obtained above was added with 20 mL of N,N-dimethylacetamide at 60 oThe polymer solid was dissolved under heating conditions at 40 °C to form a polymer solution. 0.14 g of 60% by mass sodium hydride was then added to the reaction solution and stirred evenly. 1.13 g of dipotassium 2-naphthol-6,8-disulfonic acid hydrate was then added and stirred evenly. After stirring for 30 minutes, 24 mL of dimethyl sulfoxide was added to the system and stirred. 14.4 mL of cyclohexane was then added as a desiccant. The remaining experimental steps were the same as step (2) of Example 1.

[0036] (3) Preparation of aromatic proton exchange membrane with regional disulfonic acid side chain structure: The experimental steps are the same as step (3) of Example 1.

[0037] The structural formula of the proton exchange membrane obtained in this embodiment is:

[0038] The proton exchange membrane obtained in this embodiment was tested, and the relevant steps were the same as in Example 1. The data obtained were that the proton exchange membrane 25 o The conductivity is 0.091Scm at C -1 , in 80 o The water absorption rate under C conditions was 44.1%, the corresponding swelling ratio was 12.8%, and the mass retention rate after Fenton test was 99.6%. Example 5

[0039] This embodiment provides a method for preparing an aromatic proton exchange membrane with a regional disulfonic acid side chain structure, which specifically includes the following steps: (1) Synthesis of ether-free aromatic polymer: 10 mmol of p-terphenyl, 1 mmol of 2,2,2-trifluoroacetophenone, and 9 mmol of 2,3,4,5,6-pentafluorobenzaldehyde were added to 10 mL of dichloromethane and stirred to mix thoroughly. The remaining experimental steps were the same as step (1) of Example 1.

[0040] (2) Synthesis of aromatic polymer with regional disulfonic acid side chain structure: 1 g of the skeleton-free ether aromatic polymer obtained above was added with 20 mL of N,N-dimethylacetamide at 60 o The polymer solid was dissolved under heating conditions at 40 °C to form a polymer solution. 0.35 g of sodium carbonate was then added to the reaction solution, stirred evenly, and then 1.18 g of dipotassium 2-naphthol-6,8-disulfonic acid hydrate was added and stirred evenly. The remaining experimental steps were the same as step (2) of Example 1.

[0041] (3) Preparation of aromatic proton exchange membrane with regional disulfonic acid side chain structure: The experimental steps are the same as step (3) of Example 1.

[0042] The structural formula of the proton exchange membrane obtained in this embodiment is:

[0043] The proton exchange membrane obtained in this embodiment was tested, and the relevant steps were the same as in Example 1. The data obtained were that the proton exchange membrane 25 o The conductivity is 0.112Scm at C -1 , in 80 o Under C conditions, the water absorption rate was 39.2%, the corresponding swelling ratio was 10.7%, and the mass retention rate after Fenton test was 99.4%. Comparative Example 1

[0044] This comparative example provides a method for preparing an aromatic proton exchange membrane without a regional disulfonic acid side chain structure, which specifically comprises the following steps: (1) Synthesis of ether-free aromatic polymer: The experimental steps are the same as step (1) of Example 1 (2) Sulfonation of ether-free aromatic polymer: 1 g of the ether-free aromatic polymer obtained above was added with 20 mL of N,N-dimethylacetamide at 60 o The polymer solid was dissolved under heating conditions of 100 °C to form a polymer solution. 0.37 g of potassium thiocyanate was then added to the reaction solution and mixed thoroughly. The reaction solution was then placed in an ice bath and 1.54 g of 85% by weight 3-chloroperoxybenzoic acid was slowly added. Stirring was continued for 8 hours, and the reaction solution was poured into saturated brine for precipitation. The polymer solid was then filtered to obtain a solid, which was then dissolved in dimethyl sulfoxide. The polymer solution was poured into ethyl acetate for precipitation. The dissolution and reprecipitation process was repeated three times to complete purification. The solid polymer was then dried in an oven to obtain a sulfonated solid polymer.

[0045] (3) Preparation of aromatic proton exchange membrane without regional disulfonic acid side chain structure: The experimental steps are the same as step (3) of Example 1.

[0046] The structural formula of the proton exchange membrane obtained in this comparative example is:

[0047] The proton exchange membrane obtained in this comparative example was tested, and the relevant steps were the same as those in Example 1. The data obtained were that the proton exchange membrane 25 o The conductivity is 0.54Scm at C -1 , in 80 o Under C conditions, the water absorption rate was 40.7%, the corresponding swelling ratio was 33.6%, and the mass retention rate after Fenton test was 99.1%.

[0048] The test data of the proton exchange membranes obtained in Examples 1-5 of the present invention and Comparative Example 1 are shown in Table 1.

[0049]

[0050] As shown in the table above, the ether-free backbone structure enables Examples 1-5 to exhibit excellent chemical stability, with mass retention rates exceeding 99% for each example after the Fenton test. Furthermore, the disulfonic acid groups on the side chain naphthalene rings provide Examples 1-5 with excellent proton conductivity, while the phenyl stacking effect of the side chain naphthalene rings significantly reduces water absorption and swelling of the membranes, significantly improving dimensional stability and achieving a balanced balance between proton conductivity and dimensional stability.

[0051] Figure 1 It is a synthetic route for aromatic polymers with regional disulfonic acid structures, and the synthesis of proton membranes is achieved through two steps: monomer polymerization and targeted sulfonation. Figure 2 The NMR spectra of the ether-free aromatic polymer and the aromatic polymer with a regional disulfonic acid side chain structure in Example 1 are shown, demonstrating the successful synthesis of the two polymers. Figure 3 The thermogravimetric curve changes of Example 1 before and after grafting the naphthalene ring side chain with a regional disulfonic acid group were compared. The thermogravimetric curve of Example 1 has two obvious degradation stages. The first degradation occurs in the side chain naphthalene ring sulfonic acid group, and then the main chain degradation occurs. Correspondingly, the thermogravimetric curve before the grafting of the side chain in Example 1 has only one main chain degradation stage. As can be seen from the figure, Example 1 shows excellent thermal stability. o It remains thermally stable below 30°C and can meet the requirements of use.

[0052] Figure 4 The proton conductivity of Examples 1-5 and Comparative Example 1 at different temperatures is shown. Due to the conductive advantages of the disulfonic acid groups in the side chains of Examples 1-5, the proton conductivity of Examples 1-5 is higher than that of Comparative Example 1 at all temperatures. In the comparison of the conductivity of Examples 1-5, it was found that as the amount of disulfonic acid naphthalene ring grafted in the side chain region increased, the proton conductivity of Examples 1-5 also continued to improve, reflecting the gradual improvement of the ion transport channels within the membrane. The proton conductivity of Example 5 at room temperature was 0.112 Scm -1 , in 80 o C is as high as 0.231Scm -1 .

[0053] Figure 5 The relationship between the water absorption rate of Examples 1-5 and Comparative Example 1 and the temperature is shown. Figure 6 The dimensional stability performance of Examples 1-5 and Comparative Example 1 at different temperatures is shown. Thanks to the phenyl stacking effect of the side chain naphthalene ring, Examples 1-5 exhibit good dimensional stability, and their water absorption and swelling are controlled at low levels at all temperatures.

Claims

1. An aromatic proton exchange membrane with a regional disulfonic acid side chain structure, characterized in that: The proton exchange membrane structural formula is: ， In the structural formula, n is selected from 0.5 to 0.

9.

2. A method for preparing an aromatic proton exchange membrane with a regional disulfonic acid side chain structure as claimed in claim 1, characterized in that: The following steps are involved: (1) Dissolve p-terphenyl, 2,2,2-trifluoroacetophenone and 2,3,4,5,6-pentafluorobenzaldehyde in a polymerization solvent, add trifluoromethanesulfonic acid in an ice bath and stir evenly; after the addition of trifluoromethanesulfonic acid, heat the reaction solution to 15-30 o C, carrying out polymerization reaction, after a certain period of time, the reaction is completed, the reaction solution is poured into a poor solvent for the polymer, filtered, purified, and dried to obtain an ether-free aromatic polymer; (2) dissolving the ether-free aromatic polymer in a good solvent before the polymer is sulfonated to obtain a polymer solution, and controlling the solid content of the polymer solution to be 3-8 wt %; then sequentially adding a base and 2-naphthol-6,8-disulfonic acid dipotassium hydrate to the polymer solution, and stirring evenly; then sequentially adding the good solvent after the polymer is sulfonated and cyclohexane, heating to a certain temperature range to carry out polymerization reaction, terminating the reaction after a period of reaction, drying, and purifying to obtain an aromatic polymer with a regional disulfonic acid side chain structure; (3) The aromatic polymer with a regional disulfonic acid side chain structure is dissolved in a good solvent after polymer sulfonation, and the solid content of the solution is controlled to 5wt%; after filtering and vacuuming, a casting solution is obtained, and then the casting solution is cast on a horizontal glass plate, and the solvent is dried to form a membrane; then the membrane is immersed in a 1M dilute sulfuric acid solution for 12 to 36 hours, and then the membrane surface is washed with pure water to remove free hydrogen ions to obtain an aromatic proton exchange membrane with a regional disulfonic acid side chain structure.

3. The method for preparing an aromatic proton exchange membrane with a regional disulfonic acid side chain structure according to claim 2, characterized in that: In step (1), the polymerization reaction solvent is one of dichloromethane and chloroform; the polymer poor solvent is one or more of methanol, ethanol, water and ethyl acetate; In step (2), the good solvent before the polymer is sulfonated is one of N,N-dimethylacetamide and N-methylpyrrolidone; the base is one of potassium carbonate, sodium hydroxide, potassium hydroxide, sodium hydride, and sodium carbonate; and the good solvent after the polymer is sulfonated is one of dimethyl sulfoxide and N,N-dimethylformamide.

4. The method for preparing an aromatic proton exchange membrane with a regional disulfonic acid side chain structure according to claim 2, characterized in that: In step (1), the molar ratio of p-terphenyl to trifluoromethanesulfonic acid is 1:3-10; the polymerization reaction time is 1-9 hours; In step (2), the molar amount of the ether-free aromatic polymer is calculated based on the molar amount of pentafluorobenzaldehyde monomer in the polymer, and the molar ratio of the ether-free aromatic polymer, the base, and the dipotassium 2-naphthol-6,8-disulfonic acid hydrate is 1:1.3~2:1.5~2; the volume ratio of the good solvent before the polymer sulfonation to the good solvent after the polymer sulfonation is 1:0.8~1.2; the volume ratio of the good solvent after the polymer sulfonation to cyclohexane is 1:0.4~0.

6. The polymerization reaction temperature range is 110~150 o C; time is 12~24h.

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