Aromatic proton exchange membrane with regional bisulfonic acid side chain structure and preparation method thereof

Abstract

The application provides an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure and a preparation method thereof, and belongs to the technical field of proton exchange membranes. Triphenyl, 2,2,2-trifluoroacetophenone and 2,3,4,5,6-pentafluorobenzaldehyde are selected as monomers, an aromatic polymer is obtained through a super acid polymerization method, then 2-naphthol-6,8-disulfonic acid dipotassium hydrate is added, and a double solvent method is used to successfully realize the positioning controllable sulfonation of the side chain phenyl of the polymer. The main chain of the polymer is an ether-free aromatic skeleton, which guarantees good chemical stability from the source; the flexible regional double sulfonic acid side chain is beneficial to the induction of the formation of a continuous proton transmission channel, so that excellent proton conductivity is realized; meanwhile, due to the phenyl stacking effect of the naphthyl structure of the side chain, the proton membrane has excellent dimensional stability; the application gives a solution to the contradiction that the general aromatic proton exchange membrane is difficult to be compatible with the proton conductivity and the dimensional stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of proton exchange membranes, and particularly relates to an aromatic polymer with a regional double sulfonic acid side chain structure and a preparation method thereof. BACKGROUND

[0002] Under the background of global warming and environmental crisis, it is imperative to reduce carbon emissions on a large scale in the energy and industrial system. Hydrogen energy is a clean energy with diverse sources, low carbon and wide application, and will play a key role in the reform of the energy system and the decarbonization process of the modern industrial system, and will play an important supporting role. Hydrogen energy development and utilization technology represented by fuel cell technology is gradually gaining widespread attention.

[0003] Proton exchange membranes are the core components of fuel cells, which can effectively isolate the anode and cathode of the cell and transfer protons, and at the same time serve as a support carrier for catalysts to form a membrane electrode as the main site of electrochemical reaction, playing a core role in water electrolysis and fuel cells, and having great practical significance and broad development prospects in the development of hydrogen energy. The most commercialized fuel cell separator membrane is represented by Nafion membrane, which generally has excellent electrical conductivity and reliable stability, but the high cost and harsh production conditions limit its large-scale application to some extent, so a large number of researchers are committed to the controllable preparation of low-cost aromatic proton exchange membranes.

[0004] The synthesis of aromatic proton exchange membranes can be mainly divided into two types. One is to use existing commercial aromatic polymers as raw materials, and introduce sulfonic acid groups through post-sulfonation. Although this method is relatively simple, the polymer main chain generally contains many ether bonds or heteroatoms, which are easy to absorb water and swell, resulting in poor chemical and dimensional stability of the proton exchange membrane, such as sulfonated polyether ether ketone, polyaryl ether sulfone, and polyimide. The second method is to synthesize aromatic polymers from the source for proton exchange membranes. Such polymers can be sulfonated at the monomer stage or post-sulfonated after polymerization. However, sulfonated monomers are generally difficult to use for polymerization, so post-sulfonation is generally used, such as sulfonated polyarylalkyl. In the post-sulfonation process, the chemical structure of the polymer changes before and after sulfonation, resulting in a change in the polarity of the polymer. Therefore, the solubility properties of the polymer before and after sulfonation are often different, leading to problems such as difficulty in sulfonation and uncontrollable sulfonation degree, resulting in poor conductivity of the proton exchange membrane. Therefore, the development of new proton exchange membranes with good conductivity and stability has important practical significance for the large-scale promotion of hydrogen energy. SUMMARY

[0005] The present application aims to provide a kind of aromatic proton exchange membrane with regional double sulfonic acid side chain structure and its preparation method, which places ether-free aromatic polymer in the double-solvent system composed of good solvent before polymer sulfonation and good solvent after polymer sulfonation to carry out sulfonation reaction, solves the problems of difficult sulfonation and uncontrollable sulfonation degree, and the prepared aromatic proton exchange membrane with regional double sulfonic acid side chain structure has good conductivity and stability.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] One of the technical solutions of the present application is to provide an aromatic polymer grafted with naphthol disulfonic acid on terphenyl-pentafluorobenzaldehyde copolymer, and its chemical structure is shown as follows:

[0008]

[0009] Wherein, n is selected from 0.5 to 0.9.

[0010] The aromatic proton exchange membrane with regional double sulfonic acid structure is obtained by first polymerizing p-terphenyl, 2,2,2-trifluoroacetophenone and 2,3,4,5,6-pentafluorobenzaldehyde through dehydration condensation reaction to obtain ether-free aromatic polymer, and then placing the ether-free aromatic polymer in the double-solvent system composed of good solvent before polymer sulfonation and good solvent after polymer sulfonation to complete the positioning controllable sulfonation of side chain phenyl.

[0011] The second technical solution of the present application is to provide a preparation method of the above-mentioned polymer, comprising the following steps:

[0012] (1) Dissolve p-terphenyl, 2,2,2-trifluoroacetophenone and 2,3,4,5,6-pentafluorobenzaldehyde in a polymerization reaction solvent, add trifluoromethanesulfonic acid under ice bath environment and stir uniformly; after the addition of trifluoromethanesulfonic acid is completed, heat the reaction liquid to 15-30 o C, and carry out polymerization reaction; after a certain time, the reaction is completed, pour the reaction liquid into a poor solvent for polymer, filter, purify and dry to obtain ether-free aromatic polymer;

[0013] (2) Dissolve the ether-free aromatic polymer in good solvent before polymer sulfonation to obtain polymer solution, control the solid content of the polymer solution to be 3-8wt%; then add alkali and 2-naphthol-6,8-disulfonic acid dipotassium hydrate to the polymer solution in sequence and stir uniformly; then add good solvent after polymer sulfonation and cyclohexane in sequence, heat to a certain temperature range to carry out polymerization reaction, terminate the reaction after a period of time, dry and purify to obtain aromatic polymer with regional double sulfonic acid side chain structure;

[0014] (3) the aromatic polymer with regional double sulfonic acid side chain structure is dissolved in a good solvent after polymer sulfonation, and the solid content of the solution is controlled to be 5wt%; after filtering and vacuumizing, a casting solution is obtained, and then the casting solution is cast on a horizontal glass plate, and the film is formed after drying the solvent; then the film is soaked in 1M dilute sulfuric acid solution for 12-36h, and then the film surface is washed with pure water to remove free hydrogen ions to obtain the aromatic proton exchange membrane with regional double sulfonic acid side chain structure.

[0015] Further, in step (1), the polymerization reaction solvent is one of dichloromethane and trichloromethane; the polymer poor solvent is one or more of methanol, ethanol, water and ethyl acetate; in step (2), the good solvent before polymer sulfonation 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; the good solvent after polymer sulfonation is one of dimethyl sulfoxide and N,N-dimethylformamide.

[0016] Further, 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 calculated based on the molar amount of the pentafluorobenzaldehyde monomer in the polymer, and the molar ratio of the ether-free aromatic polymer, the base and 2-naphthol-6,8-disulfonic acid dipotassium hydrate is 1:1.3-2:1.5-2; the volume ratio of the good solvent before polymer sulfonation to the good solvent after polymer sulfonation is 1:0.8-1.2; the volume ratio of the good solvent after polymer sulfonation to cyclohexane is 1:0.4-0.6; the polymerization reaction temperature range is 110-150 o C; the time is 12-24h.

[0017] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0018] (1) The aromatic proton exchange membrane with regional double sulfonic acid side chain structure provided by the present application has a polymer structure of aromatic polymer backbone plus naphthalene ring double sulfonic acid side chain structure, and the naphthalene ring structure in the side chain has a strong phenyl stacking effect, which makes the polymer chain stack closely and the overall water swelling small, and exhibits high dimensional stability, thereby achieving the balance between the conductivity and the dimensional stability of the proton membrane.

[0019] (2) The method of the present application places the ether-free aromatic polymer in a double-solvent system composed of a good solvent before polymer sulfonation and a good solvent after polymer sulfonation to carry out sulfonation reaction, which solves the problems of sulfonation difficulty and uncontrollable sulfonation degree caused by the change of solubility before and after polymer sulfonation due to the change of polarity.

[0020] (3) The method of the present application successfully introduces a regional double sulfonic acid side chain structure by grafting 2-naphthol-6,8-disulfonic acid dipotassium on the polymer main chain. The presence of the regional double sulfonic acid side chain structure to some extent realizes the enrichment of sulfonic acid groups, and exhibits more superior proton conduction performance than traditional single sulfonic acid side chains, effectively improving the conductivity of the proton exchange membrane.

[0021] (4) The method of the present application uses triphenyl, pentafluorobenzaldehyde and trifluorophenylacetone as polymer monomers, realizes polymerization by super acid polymerization method, constructs a polymer ether-free main chain, and the side chain mainly uses aromatic naphthalene ring, which has good chemical stability. Experiments show that the proton membrane remains intact after Fenton test and the mass retention rate is above 99%. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is the synthesis route diagram of the aromatic polymer with a regional double sulfonic acid side chain in the present application embodiment 1.

[0023] Figure 2 It is the nuclear magnetic resonance spectrum of the ether-free aromatic polymer and the aromatic polymer with a regional double sulfonic acid side chain in the present application embodiment 1.

[0024] Figure 3 It is the thermogravimetric spectrum of the aromatic polymer with a regional double sulfonic acid side chain structure before and after sulfonation in the present application embodiment 1.

[0025] Figure 4 It is the conductivity change trend graph of the aromatic proton exchange membrane with a regional double sulfonic acid side chain structure in the present application embodiments 1-5 and the aromatic proton exchange membrane without a regional double sulfonic acid side chain structure in the comparative example 1 with temperature.

[0026] Figure 5 It is the water absorption change trend graph of the aromatic proton exchange membrane with a regional double sulfonic acid side chain structure in the present application embodiments 1-5 and the aromatic proton exchange membrane without a regional double sulfonic acid side chain structure in the comparative example 1 with temperature.

[0027] Figure 6 It is the swelling ratio change trend graph of the aromatic proton exchange membrane with a regional double sulfonic acid side chain structure in the present application embodiments 1-5 and the aromatic proton exchange membrane without a regional double sulfonic acid side chain structure in the comparative example 1 with temperature. DETAILED DESCRIPTION

[0028] The embodiments of the present application will be described below in conjunction with specific implementation cases, but the embodiments of the present application are not limited to the following specific implementation schemes. It should be understood that researchers in the field of the present application can obtain other embodiments similar to the present application without creative labor, which are within the scope of protection of the present application.

[0029] It should be understood that, unless otherwise defined, technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. Example 1

[0030] The present embodiment provides a preparation method of aromatic proton exchange membrane with regional double sulfonic acid side chain structure, which specifically comprises the following steps:

[0031] (1) Synthesis of ether-free aromatic polymer: 10 mmol of p-terphenyl, 5 mmol of 2,2,2-trifluoroacetophenone and 5 mmol of 2,3,4,5,6-pentafluorobenzaldehyde are added to 10 mL of dichloromethane (CH2Cl2), the mixture is stirred until completely mixed, then the reaction solution is cooled in an ice bath environment for 15 min, after cooling, 8 mL of trifluoromethanesulfonic acid (TFSA) is slowly added to the reaction solution; then the reaction solution is continuously reacted at 30°C for 1 h, then the reaction completed solution is poured into methanol to form white fibrous polymer precipitate, which is filtered, dried, then dissolved in N,N-dimethylacetamide, and then the polymer solution is poured into methanol for the first purification, after three times of purification, the polymer solid is dried in an oven to obtain the ether-free aromatic polymer.

[0032] (2) Synthesis of aromatic polymer with regional double sulfonic acid side chain structure: 1 g of the ether-free aromatic polymer obtained above is added, then 20 mL of N,N-dimethylacetamide is added to dissolve the polymer solid to form a polymer solution under the condition of heating at 60 o C; then 0.26 g of potassium carbonate is added to the reaction system, stirred uniformly, then 0.72 g of 2-naphthol-6,8-disulfonic acid dipotassium hydrate is added and stirred uniformly; after stirring for 30 min, 20 mL of dimethyl sulfoxide is added and stirred; then 10 mL of cyclohexane is added as a water removal agent, then the reaction system is heated to 110 o C, and after continuously stirring for 24 h, the reaction solution is poured into a tray and dried in an oven to obtain a solid, then the polymer solid is washed with pure water to remove water-soluble impurities, then the washed polymer solid is dried in an oven, dissolved in dimethyl sulfoxide to obtain a polymer solution, and the polymer solution is poured into methanol for precipitation, and the purification is repeated for 3 times to obtain the aromatic polymer with regional double sulfonic acid side chain structure.

[0033] (3) Preparation of aromatic proton exchange membrane with regional double sulfonic acid side chain structure: 1 g of the aromatic polymer with regional double sulfonic acid side chain structure is dissolved in 20 mL of dimethyl sulfoxide to form a polymer solution under the condition of heating at 60 o C, then the polymer solution is filtered through a sand core funnel to remove insoluble impurities to obtain a film injection solution; then the film injection solution is poured on a flat glass plate, 60o C for 12 h, then the glass plate was placed in pure water for 30 min, at this time the membrane was completely separated from the glass plate, then the membrane was taken out and immersed in a dilute sulfuric acid solution of 1 mol / L for 24 h, after that the membrane was taken out and the free acid on the surface of the membrane was washed with deionized water to obtain an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure.

[0034] The proton exchange membrane obtained in this example has the following structural formula:

[0035]

[0036] The aromatic proton exchange membrane with a regional double sulfonic acid side chain structure obtained in this example was cut into a 1x4 cm long strip and placed in a conductivity test fixture, and its conductivity was tested using a 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 water absorption at different temperatures were measured, and the water absorption rate and swelling ratio of the proton exchange membrane were obtained by comparing the corresponding data with the dry data. At the same time, the proton exchange membrane was placed in 60 o C Fenton reagent for 1 h to test its oxidation stability. It was found that the conductivity of the proton exchange membrane obtained in this example was 0.068 Scm o at 25 -1 C, the water absorption rate was 31.5% under the condition of 80 o C, and the corresponding swelling ratio was only 14.2%, and the mass retention rate after Fenton test was 99.7%. Example 2

[0037] This example provides a method for preparing an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure, which specifically comprises the following steps:

[0038] (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 until the mixture was completely mixed. Then the reaction solution was cooled in an ice bath environment for 15 min, and after cooling, trifluoromethanesulfonic acid (TFSA) 2.7 mL was slowly added to the reaction solution. Then the reaction solution was placed at 30°C for continuous reaction for 9 h, and then the reaction completed solution was poured into ethanol to form white fibrous polymer precipitate. The remaining experimental steps are the same as step (1) of Example 1.

[0039] (2) Synthesis of aromatic polymer with regional double sulfonic acid side chain structure: 1 g of the aforementioned obtained backbone ether-free aromatic polymer was added to 20 mL of N,N-dimethylacetamide at 60 oC. The polymer solid was dissolved under heating to form a polymer solution. Then, 0.078 g of sodium hydroxide was added to the reaction solution, which was stirred uniformly. Then, 0.74 g of 2-naphthol-6,8-disulfonic acid dipotassium hydrate was added and stirred uniformly. After 30 minutes of stirring, 20 mL of N,N-dimethylformamide was added to the system and stirred. Then, 10 mL of cyclohexane was added as a water removal agent, and then the reaction system was heated to 130 o C. After 19 h of continuous stirring, the reaction solution was poured into a tray and dried in an oven to obtain a solid. The remaining experimental steps were the same as those in step (2) of Example 1.

[0040] (3) Preparation of an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure: The experimental steps were the same as those in step (3) of Example 1.

[0041] The proton exchange membrane obtained in this example has the following structural formula:

[0042]

[0043] The proton exchange membrane obtained in this example was tested, and the relevant steps were the same as those in Example 1. The data obtained for the proton exchange membrane were as follows: the conductivity of the proton exchange membrane at 25 o C was 0.078 Scm -1 The water absorption rate of the proton exchange membrane at 80 o C was 33.9%, the corresponding swelling ratio was 16.1%, and the mass retention rate after Fenton test was 99.3%. Example 3

[0044] This example provides a method for preparing an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure, which specifically comprises the following steps:

[0045] (1) Synthesis of an 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, which was stirred until the mixture was completely mixed. Then, the reaction solution was cooled in an ice bath environment for 15 min. After cooling, 8.8 mL of trifluoromethanesulfonic acid (TFSA) was slowly added to the reaction solution. Then, the reaction solution was continuously reacted at 30°C for 1 h. Then, the reaction completed solution was poured into water to form a white fibrous polymer precipitate. The remaining experimental steps were the same as those in step (1) of Example 1.

[0046] (2) Synthesis of an aromatic polymer with a regional double sulfonic acid side chain structure: 1 g of the aforementioned obtained backbone ether-free aromatic polymer was added to 20 mL of N-methylpyrrolidone, which was heated to 60 oC. The polymer solid is dissolved under heating to form a polymer solution; then 0.2 g of potassium hydroxide is added to the reaction solution, which is stirred until uniform, and then 1.33 g of 2-naphthol-6,8-disulfonic acid dipotassium hydrate is added and stirred until uniform. After stirring for 30 min, 16 mL of dimethyl sulfoxide is added to the system as a dehydrating agent, and then the reaction system is heated to 150 o C, and stirring is continued for 12 h. The remaining experimental steps are the same as those in step (2) of Example 1.

[0047] (3) Preparation of an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure: the experimental steps are the same as those in step (3) of Example 1.

[0048] The proton exchange membrane obtained in this example has the following structural formula:

[0049]

[0050] The proton exchange membrane obtained in this example is tested, and the relevant steps are the same as those in Example 1. The data obtained for the proton exchange membrane are as follows: the conductivity of the proton exchange membrane at 25 o C is 0.086 S cm -1 , the water absorption rate under the condition of 80 o C is 42.4%, the corresponding swelling ratio is 15.5%, and the mass retention rate after Fenton test is 99.4%. Example 4

[0051] This example provides a method for preparing an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure, which specifically includes the following steps:

[0052] (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 are added to 10 mL of dichloromethane, which is stirred until uniform. Then the reaction solution is cooled in an ice bath environment for 15 min, and then 4.4 mL of trifluoromethanesulfonic acid (TFSA) is slowly added to the reaction solution. Then the reaction solution is continuously reacted at 30 °C for 5 h, and then the reaction completed solution is poured into ethyl acetate to form white fibrous polymer precipitates. The remaining experimental steps are the same as those in step (1) of Example 1.

[0053] (2) Synthesis of aromatic polymer with a regional double sulfonic acid side chain structure: 1 g of the aforementioned obtained backbone ether-free aromatic polymer is taken, and then 20 mL of N,N-dimethylacetamide is added at 60 oC under heating condition to form a polymer solution; then 0.14 g of 60% sodium hydride by mass fraction was added into the reaction solution, and after stirring uniformly, 1.13 g of 2-naphthol-6,8-disulfonic acid dipotassium hydrate was added and stirred uniformly, and after stirring for 30 minutes, 24 mL of dimethyl sulfoxide was added and stirred; and 14.4 mL of cyclohexane was added as a water removal agent. The remaining experimental steps were the same as those in step (2) of Example 1.

[0054] (3) Preparation of the aromatic proton exchange membrane with the regional double sulfonic acid side chain structure: the experimental steps were the same as those in step (3) of Example 1.

[0055] The proton exchange membrane obtained in this example had the following structural formula:

[0056]

[0057] The proton exchange membrane obtained in this example was tested, and the relevant steps were the same as those in Example 1. The obtained data of the proton exchange membrane were as follows: the conductivity at 25 o C was 0.091 S cm -1 , the water absorption rate under the condition of 80 o C was 44.1%, the corresponding swelling ratio was 12.8%, and the mass retention rate after Fenton test was 99.6%. Example 5

[0058] This example provided a preparation method of an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure, which specifically included the following steps:

[0059] (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 into 10 mL of dichloromethane, and the mixture was stirred until completely mixed. The remaining experimental steps were the same as those in step (1) of Example 1.

[0060] (2) Synthesis of aromatic polymer with regional double sulfonic acid side chain structure: 1 g of the skeleton ether-free aromatic polymer obtained above was taken, and then 20 mL of N,N-dimethylacetamide was added under heating at 60 o C under heating condition to form a polymer solution; then 0.14 g of 60% sodium hydride by mass fraction was added into the reaction solution, and after stirring uniformly, 1.13 g of 2-naphthol-6,8-disulfonic acid dipotassium hydrate was added and stirred uniformly, and after stirring for 30 minutes, 24 mL of dimethyl sulfoxide was added and stirred; and 14.4 mL of cyclohexane was added as a water removal agent. The remaining experimental steps were the same as those in step (2) of Example 1.

[0061] (3) Preparation of the aromatic proton exchange membrane with the regional double sulfonic acid side chain structure: the experimental steps were the same as those in step (3) of Example 1.

[0062] The proton exchange membrane obtained in this example had the following structural formula:

[0063]

[0064] The proton exchange membrane obtained in this example was tested, and the relevant steps were the same as in Example 1. The data obtained for the proton exchange membrane were as follows: 25 o The conductivity at 25°C was 0.112 S cm -1 The water uptake at 80 o C was 39.2%, the corresponding swelling ratio was 10.7%, and the mass retention rate after Fenton test was 99.4%. Comparative Example 1

[0065] This comparative example provides a preparation method of an aromatic proton exchange membrane without a regional double sulfonic acid side chain structure, specifically comprising the following steps:

[0066] (1) Synthesis of ether-free aromatic polymer: the experimental steps were the same as in step (1) of Example 1.

[0067] (2) Sulfonation of ether-free aromatic polymer: 1 g of the ether-free aromatic polymer obtained above was taken, and 20 mL of N,N-dimethylacetamide was then added to dissolve the polymer solid under heating at 60 o C to form a polymer solution; then 0.37 g of potassium thiocyanate was added to the reaction solution and mixed uniformly, and then the reaction solution was placed in an ice bath environment, 1.54 g of 3-chloroperbenzoic acid with a mass fraction of 85% was slowly added, and stirring was continued for 8 h. The reaction solution was poured into saturated brine for precipitation. Then the polymer solid was obtained by filtration, and was dissolved in dimethyl sulfoxide. The polymer solution was poured into ethyl acetate for precipitation, and the dissolution and precipitation operation was repeated 3 times to complete the purification. The polymer solid was placed in an oven for drying to obtain the sulfonated polymer solid.

[0068] (3) Preparation of an aromatic proton exchange membrane without a regional double sulfonic acid side chain structure: the experimental steps were the same as in step (3) of Example 1.

[0069] The structural formula of the proton exchange membrane obtained in this comparative example was as follows:

[0070]

[0071] The proton exchange membrane obtained in this comparative example was tested, and the relevant steps were the same as in Example 1. The data obtained for the proton exchange membrane were as follows: 25 o The conductivity at 25°C was 0.54 S cm -1 The water uptake at 80 o C was 40.7%, the corresponding swelling ratio was 33.6%, and the mass retention rate after Fenton test was 99.1%.

[0072] The test data of the proton exchange membranes obtained in Examples 1-5 and Comparative Example 1 of the present application were summarized in Table 1.

[0073]

[0074] From the above table, the ether-free main chain design makes examples 1-5 exhibit excellent chemical stability, and the mass retention rate of each example after Fenton test is above 99%. At the same time, the double sulfonic acid groups on the side chain naphthalene ring provide excellent proton conductivity for examples 1-5, and the phenyl stacking effect of the side chain naphthalene ring significantly reduces the water absorption and swelling of the film, significantly improves the dimensional stability, and realizes the balance of proton conductivity and dimensional stability.

[0075] Figure 1 is the synthesis route of aromatic polymer with regional double sulfonic acid structure, which realizes the synthesis of proton membrane through two steps of monomer polymerization and positioning sulfonation. Figure 2 The nuclear magnetic resonance spectra of the ether-free aromatic polymer in example 1 and the aromatic polymer with regional double sulfonic acid side chain structure are shown, which proves the successful synthesis of the two polymers. Figure 3 The thermal gravimetric curve changes of example 1 before and after grafting with naphthalene ring side chain with regional double sulfonic acid group are compared. The thermal gravimetric curve of example 1 has two obvious degradation stages, the first is the degradation of the side chain naphthalene ring sulfonic acid group, and then the main chain degradation occurs. Correspondingly, the thermal gravimetric curve of example 1 before grafting with side chain only has one main chain degradation stage. As can be seen from the figure, example 1 exhibits excellent thermal stability, and remains thermally stable at 200 o C, which can meet the use requirements.

[0076] Figure 4 The proton conductivity of examples 1-5 and comparative example 1 at different temperatures is shown. Due to the conductive advantage of the regional double sulfonic acid group of the side chain of examples 1-5, the proton conductivity of examples 1-5 is higher than that of comparative example 1 at each temperature. In the conductivity comparison of examples 1-5, it is found that with the increase of the grafting amount of the side chain regional double sulfonic acid naphthalene ring, the proton conductivity of examples 1-5 also continuously increases, which reflects the gradual improvement of the ion transmission channel in the film. The proton conductivity of example 5 at room temperature is 0.112 Scm -1 , and the proton conductivity of example 5 at 80 o C is as high as 0.231 Scm -1 .

[0077] Figure 5 The water absorption rate of examples 1-5 and comparative example 1 with temperature change is shown, Figure 6 The dimensional stability of examples 1-5 and comparative example 1 at different temperatures is shown. Due to the phenyl stacking effect of the side chain naphthalene ring, examples 1-5 exhibit good dimensional stability, and the water absorption and swelling are controlled at a low level at each temperature.

Claims

1. A method for preparing an aromatic proton exchange membrane with a regionally bis-sulfonic acid side chain structure, characterized by, The method comprises 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 under ice bath environment and stir uniformly; after the addition of trifluoromethanesulfonic acid is completed, warm the reaction liquid to 15~30 o C, and conduct polymerization reaction; after a certain time, the reaction is completed; pour the reaction liquid into a poor solvent of the polymer, filter, purify and dry to obtain an ether-free aromatic polymer; the total mole fraction of the prepared ether-free aromatic polymer is 1, wherein the mole fraction of the structural units corresponding to p-terphenyl and 2,2,2-trifluoroacetophenone is 1-n, and the mole fraction of the structural units corresponding to p-terphenyl and 2,3,4,5,6-pentafluorobenzaldehyde is n, and n is selected from 0.5-0.9; (2) dissolving the ether-free aromatic polymer in a good solvent before polymer sulfonation to obtain a polymer solution, controlling the solid content of the polymer solution to be 3-8 wt%; then adding alkali and 2-naphthol-6,8-disulfonic acid dipotassium hydrate into the polymer solution in sequence, stirring uniformly; then adding a good solvent after polymer sulfonation and cyclohexane in sequence, heating to a certain temperature range for polymerization reaction, terminating the reaction after a period of time, drying and purifying to obtain an aromatic polymer with a regional double sulfonic acid side chain structure; (3) dissolving the aromatic polymer with a regional double sulfonic acid side chain structure in a good solvent after polymer sulfonation, and controlling the solid content of the solution to be 5 wt%; after filtration and vacuum extraction, a casting solution is obtained, which is then cast on a horizontal glass plate, and a film is formed after drying the solvent; then the film is soaked in a 1M dilute sulfuric acid solution for 12-36h, and then washed with pure water to remove free hydrogen ions on the film surface to obtain an aromatic proton exchange membrane with a regional double sulfonic acid side chain structure; In step (1), the molar ratio of the terphenyl to trifluoromethanesulfonic acid is 1:3-10; and the polymerization reaction time is 1-9h. In step (2), the molar ratio of the ether-free aromatic polymer, the base, and 2-naphthol-6,8-disulfonic acid dipotassium hydrate is 1:1.3~2:1.5~2, based on the molar amount of the pentafluorobenzaldehyde monomer in the polymer, the volume ratio of the good solvent before polymer sulfonation and the good solvent after polymer sulfonation is 1:0.8~1.2, the volume ratio of the good solvent after polymer sulfonation and cyclohexane is 1:0.4~0.6, and the polymer sulfonation temperature is 110~150 o C; the time is 12~24h.

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

3. An aromatic proton exchange membrane having a regionally bis-sulfonic acid side chain structure, characterized by, The aromatic proton exchange membrane with a regional double sulfonic acid side chain structure is prepared by the preparation method in claim 1 or 2.

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