A polyaromatic hydrocarbon for preparing proton exchange membranes, its preparation method and application

Abstract

This invention discloses a polyaromatic hydrocarbon for preparing proton exchange membranes, its preparation method, and its application, belonging to the field of proton exchange membrane material preparation technology. This invention solves problems such as low molecular weight, uneven sulfonation, chain breakage in sulfonated polymers, poor dimensional stability, and poor mechanical properties in proton exchange membrane materials. Using aromatic monomers and 3,5-difluorotrifluoroacetophenone as raw materials, this invention employs a superacid-catalyzed Friedel-Crafts hydroxyalkylation reaction to prepare fluorinated aromatic polymers. Then, sulfonic acid groups are introduced onto the fluorinated aromatic polymers via nucleophilic substitution followed by sulfonation, preparing monosulfonated and disulfonated fluorinated sulfonic acid polymers. Proton exchange membranes are then prepared using these polymers as raw materials. The significant polarity difference between the hydrophobic fluorinated benzene ring side groups and the hydrophilic disulfonic acid groups in this invention is more conducive to forming a microphase separation structure and constructing continuous proton transport channels. Simultaneously, the hydrophobic fluorinated segments effectively suppress membrane swelling and improve its dimensional stability.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane material preparation technology, specifically relating to a polyaromatic hydrocarbon for preparing proton exchange membranes, its preparation method, and its application. Background Technology

[0002] The use of traditional energy sources has led to increasingly serious energy and resource shortages in modern society, and the excessive use of fossil fuels and the emission of sulfur and nitrogen oxides from burning fossil fuels have caused environmental pollution. Against this backdrop, the development of renewable energy utilization systems and energy storage and conversion devices based on membrane technology is of great significance. Polymer electrolyte membrane fuel cells and redox flow batteries are clean and efficient power generation technologies. Among them, a fuel cell is a device that directly converts chemical energy into electrical energy through electrode reactions. As the core component of a fuel cell, the performance of the proton exchange membrane directly determines the efficiency, stability and service life of the entire battery system. The proton exchange membrane generally needs to meet the following characteristics: (1) high proton conductivity; (2) good thermal stability and mechanical properties; (3) high oxidation stability and good anti-swelling ability; (4) appropriate cost-performance ratio, etc. Currently, the polymer electrolytes that can be used as proton exchange membranes are mainly: perfluorosulfonic acid type proton exchange membranes, non-fluorosulfonic acid type proton exchange membranes and some fluorosulfonic acid type proton exchange membranes.

[0003] Perfluorosulfonic acid proton exchange membranes, represented by DuPont's Nafion membrane, are a class of functional materials composed of a hydrophobic polytetrafluoroethylene backbone and hydrophilic sulfonic acid side chains. Due to the hydrophobic perfluorinated backbone, the carbon-fluorine bonds in the Nafion membrane endow it with excellent oxidative and thermal stability in strong acid, strong alkali, and strong redox environments. Simultaneously, the hydrophilic sulfonic acid side chains interact with the hydrophobic backbone to form a phase-separated structure, providing a channel for proton transport. Although Nafion membranes exhibit good proton conductivity and stability, they still have the following limitations, restricting their application range: (1) high cost; (2) limited high-temperature performance; (3) high permeability to fuels such as methanol; (4) strong temperature dependence of proton conductivity; and (5) difficulty in modification, making it difficult to adjust their performance through chemical modification. Therefore, developing sulfonated polymer membranes that are inexpensive and possess good thermal stability, chemical properties, and high proton conductivity has become an important direction for development in this field.

[0004] Compared to traditional perfluorosulfonic acid proton exchange membranes, such as Nafion membranes, sulfonated aromatic polymer membranes have become a focus of research in recent years due to their advantages such as good thermal stability, lower preparation cost, and ease of molecular structure control and modification. Sulfonated polyaromatic proton exchange membranes can be mainly classified into sulfonated polyphenylene ethers, sulfonated polybenzimidazoles, sulfonated polyphenylene, and sulfonated polyaromatics, depending on their main chain structure. Studies have shown that sulfonated aromatic polymer membranes containing ether bonds in the main chain are susceptible to free radical attack in acidic oxidizing environments, leading to main chain breakage and thus limiting their application in fuel cells. Analysis of dissociation bond energies shows that the dissociation energy of the aryl-ether bond-aryl (Ar-O-Ar) in the polyaryl ether segment is 332.2 ± 8.4 kJ / mol. -1 The dissociation energy of the aryl-alkyl-aryl group in the polyaryl hydrocarbon segment (Ar-C-Ar) is 378.2 ± 8.4 kJ / mol. -1 This proves that the dissociation energy of Ar-C-Ar is higher than that of Ar-O-Ar.

[0005] Etherless sulfonated polyaromatics can be prepared through pre-functionalization and post-functionalization methods. The pre-functionalization method utilizes ketone monomers containing sulfonic acid groups to polymerize with aromatic compounds to obtain sulfonated polymers, allowing for effective control of the degree of sulfonation and the distribution of sulfonic acid groups. Professor Rakel's team (Khataee, Amirreza, et al. "Poly (arylene alkylene) sfunctionalized with perfluorosulfonic acid groups as proton exchange membranes for vanadium redox flow batteries." Journal of Membrane Science 671 (2023): 121390.) used 2,2,2-trifluoroacetophenone functionalized with terphenyl and perfluorosulfonic acid as monomers to prepare proton exchange membranes with highly acidic perfluorosulfonic acid side chains via superacid-catalyzed polymerization, achieving proton conductivity superior to commercial Nafion membranes. However, sulfonated ketone monomers typically require complex preparation and purification processes, and due to the influence of sulfonic acid groups on the polymerization reaction, obtaining high molecular weight polymers is difficult.

[0006] Compared with the pre-functionalization method, the post-functionalization method has the advantages of preparing higher molecular weight ionomers and membrane materials with superior mechanical properties. Kim's research team used trifluoroacetophenone, indigo, and biphenyl as monomers to synthesize ether-free poly(N-methylindigo-biphenyl) via superacid catalysis, and further prepared ionomers with an IEC range of 1.43-2.39 meqg by post-sulfonation with concentrated sulfuric acid. -1The proton conductivity of the obtained polyarylene proton exchange membrane is slightly lower than that of the Nafion 211 membrane. Ryu T, Ahmed F, Sutradhar SC, et al. Synthesis and characterization of block copolymer and comparative study with random copolymer via superacid-catalyzed reaction[J]. International Journal of Hydrogen Energy, 2018, 43(26): 11862-11871. Compared with the advantages of the pre-functionalization method in terms of sulfonation site determination and IEC controllability, the post-functionalization method has the disadvantages of difficult sulfonation site control and easy over-sulfonation. To solve the above problems, the strategy of introducing sulfonic acid groups by nucleophilic substitution-oxidation reaction can be adopted. Professor Kerres' team (Li W, Zhang R, Zhao X, et al. Highly proton conductive and stable sulfonated poly(arylene-alkane) for fuel cells with performance over 2.46W cm -2 [J]. Journal of Materials Chemistry A, 2023, 11(9): 4547-4558.) Sulfonated polymers were prepared by thiolation-oxidation of polyethersulfone containing pentafluorophenyl groups using sodium hydrosulfide. Fluoropolymers with monosulfonic acid benzene ring units were prepared by utilizing the fluorine atom to locate the substitution sites and number of sulfonic acid groups. Current research on the preparation of sulfonated polymers by sodium hydrosulfide substitution method mainly focuses on monosubstituted aromatic rings, while research on polysubstituted monophenyl rings is relatively limited.

[0007] In summary, the main drawbacks of existing main-chain ether-free polymerization techniques are: (1) the pre-functionalization method for preparing sulfonated polymers is limited by the reactivity of the sulfonated monomers, making it difficult to obtain high molecular weight polymers; (2) the post-functionalization method uses sulfonating reagents to introduce sulfonic acid groups, which has problems such as difficulty in controlling the degree of sulfonation, uneven sulfonation, and chain breakage of sulfonated polymers; (4) sulfonated polymer films with high sulfonation degree have problems such as poor dimensional stability and poor mechanical properties. Summary of the Invention

[0008] To overcome the aforementioned problems in the prior art, this invention provides a polyaromatic hydrocarbon for preparing proton exchange membranes, its preparation method, and its application.

[0009] The technical solution of the present invention is as follows: One objective of this invention is to provide a polyaromatic hydrocarbon for preparing proton exchange membranes, wherein the polyaromatic hydrocarbon is a monosulfonated fluorosulfonic acid polymer or a bissulfonated fluorosulfonic acid polymer, the structure of the monosulfonated fluorosulfonic acid polymer is shown in Formula I, and the structure of the bissulfonated fluorosulfonic acid polymer is shown in Formula II. Formula I, Formula II, Where x > 0, y ≥ 0, and y:x = (0-1):(0.7-0.1), the structure of Ar1 is shown in Equation III or Equation IV: Formula III, Formula IV.

[0010] Further specify, x > 0, y ≥ 0, and y:x = (0-1):(0.5-0.1).

[0011] A second objective of this invention is to provide a method for preparing the above-mentioned polyaromatic hydrocarbon, the method comprising: (1) Synthesis of fluorinated precursor polymer: Aromatic monomers and 3,5-difluorotrifluoroacetophenone were dissolved in a solvent at 0℃, and trifluoromethanesulfonic acid was added dropwise after stirring to carry out the reaction. The mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain the fluorinated precursor polymer. (2) Synthesis of substitution product 1: The fluorine-containing precursor polymer was dissolved in a solvent and sodium hydrosulfide was introduced under a nitrogen atmosphere to obtain a reaction system. The substitution reaction was carried out, and the mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain substitution product 1. (3) Synthesis of polyaromatic hydrocarbons: The substituted product 1, glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water are mixed and oxidized. The mixture after the reaction is filtered, washed and vacuum dried to obtain polyaromatic hydrocarbons with the structure shown in Formula I, namely monosulfonated fluorosulfonic acid polymers.

[0012] Further specify that (1) the aromatic monomer is terphenyl or biphenyl, and the solvent is dichloromethane, chloroform or tetrachloroethane.

[0013] Further specified, in (1), the molar ratio of aromatic monomer to 3,5-difluorotrifluoroacetophenone is 1:(1.05-1.2), and the molar ratio of aromatic monomer to trifluoromethanesulfonic acid is 1:(1-1.5).

[0014] Further, the reaction temperature in (1) is 20-30℃ and the time is 0.5-48h.

[0015] Further specifying, the structure of the fluorinated precursor polymer in (1) is as shown in formula V (PDPtf) or formula VI (PTPtf): Formula V, VI, Where x > 0 and y > 0.

[0016] Further specifying, in (1), when biphenyl is used, the structure of the fluorinated precursor polymer obtained is shown in Formula V; when terphenyl is used, the structure of the fluorinated precursor polymer obtained is shown in Formula VI.

[0017] Further specifying, in (2), the solvent is N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone.

[0018] Further specified, in (2), the molar ratio of sodium hydrosulfide to fluorinated precursor polymer is (1.5-4):1; the substitution reaction temperature is 50-150℃, the time is 8-20h; and the solid content of the reaction system is 5-20%.

[0019] Furthermore, the molar ratio of sodium hydrosulfide to the fluorinated precursor polymer is (2-3):1; the substitution reaction temperature is 80-140℃, the time is 10-15h; and the solid content of the reaction system is 8-15%.

[0020] Further specifying, the mass-volume ratio of the substituted product 1 in (3) to glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water is 1g: (3-13)mL: (0.5-5)mL: (2-4)mL: (1-5)mL.

[0021] Further, the oxidation reaction temperature in (3) is 20-40℃ and the time is 20-40h.

[0022] Furthermore, the oxidation reaction temperature is specified as 25-30℃, and the time is specified as 20-30h.

[0023] A third objective of this invention is to provide a method for preparing the above-mentioned polyaromatic hydrocarbon, the method comprising: (1) Synthesis of fluorinated precursor polymer: Aromatic monomers and 3,5-difluorotrifluoroacetophenone were dissolved in a solvent at 0℃, and trifluoromethanesulfonic acid was added dropwise after stirring. The reaction was carried out at room temperature for 2 hours. The mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain the fluorinated precursor polymer. (2) Synthesis of substitution product 1: The fluorine-containing precursor polymer was dissolved in a solvent, and sodium hydrosulfide was introduced under a nitrogen atmosphere to carry out the substitution reaction. The mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain substitution product 1. (3) Synthesis of monosulfonated fluorosulfonic acid polymer: Substitution product 1, glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water are mixed and oxidized. The mixture after reaction is filtered, washed and vacuum dried to obtain monosulfonated fluorosulfonic acid polymer. (4) Synthesis of substitution product 2: The monosulfonated fluorosulfonic acid polymer was dissolved in a solvent and sodium hydrosulfide was added under a nitrogen atmosphere to carry out the substitution reaction. The mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain substitution product 2. (5) Synthesis of polyaromatic hydrocarbons: The substituted product 2, glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water are mixed and oxidized. The mixture after the reaction is filtered, washed and vacuum dried to obtain polyaromatic hydrocarbons with the structure shown in Formula II, namely, double sulfonated fluorosulfonic acid polymers.

[0024] Further specify that (1) the aromatic monomer is terphenyl or biphenyl, and the solvent is dichloromethane, chloroform or tetrachloroethane.

[0025] Further specified, in (1), the molar ratio of aromatic monomer to 3,5-difluorotrifluoroacetophenone is 1:(1.05-1.2), and the molar ratio of aromatic monomer to trifluoromethanesulfonic acid is 1:(1-1.5).

[0026] Further, the reaction temperature in (1) is 20-30℃ and the time is 0.5-48h.

[0027] Further specifying, the structure of the fluorinated precursor polymer in (1) is as shown in formula V (PDPtf) or formula VI (PTPtf): Formula V, VI, Where x is greater than 0 and y is greater than 0.

[0028] Further specifying, in (1), when biphenyl is used, the structure of the fluorinated precursor polymer obtained is shown in Formula V; when terphenyl is used, the structure of the fluorinated precursor polymer obtained is shown in Formula VI.

[0029] Further specifying, in (2), the solvent is N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone.

[0030] Further specified, in (2), the molar ratio of sodium hydrosulfide to fluorinated precursor polymer is (1.5-4):1; the substitution reaction temperature is 50-150℃, the time is 8-20h; and the solid content of the reaction system is 5-20%.

[0031] Furthermore, the molar ratio of sodium hydrosulfide to the fluorinated precursor polymer is (2-3):1; the substitution reaction temperature is 80-140℃, the time is 10-15h; and the solid content of the reaction system is 8-15%.

[0032] Further, the oxidation reaction temperature in (3) is 20-40℃ and the time is 20-40h.

[0033] Furthermore, the oxidation reaction temperature is specified as 25-30℃, and the time is specified as 20-30h.

[0034] Further specified, in (4), the molar ratio of sodium hydrosulfide to monosulfonated fluorosulfonic acid polymer is (1.5-4):1; the substitution reaction temperature is 20-40℃, the time is 10-20h; and the solid content of the reaction system is 5-20%.

[0035] Furthermore, the molar ratio of sodium hydrosulfide to monosulfonated fluorosulfonic acid polymer is (2-3):1; the substitution reaction temperature is 25-30℃, the time is 12-15h; and the solid content of the reaction system is 8-15%.

[0036] Further specifying, the mass-volume ratio of the substituted product 2 in (5) to glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water is 1g: (1-3)mL: (0.25-1)mL: (0.5-1.5)mL: (0.5-2)mL.

[0037] Further, the oxidation reaction temperature in (5) is 20-40℃ and the time is 20-50h.

[0038] Furthermore, the oxidation reaction temperature is specified as 25-30℃, and the time is specified as 30-40h.

[0039] The fourth objective of this invention is to provide a proton exchange membrane that uses the aforementioned polyaromatic hydrocarbon as the film-forming material. The fifth objective of this invention is to provide a method for preparing the above-mentioned proton exchange membrane, the method comprising the following steps: (1) Dissolve polyaromatic hydrocarbon (monosulfonated or bissulfonated polymer) in a solvent to obtain a casting solution, cast the casting solution onto a glass plate to form a film, and dry it to obtain a homogeneous film; (2) The homogeneous membrane is first soaked in water, then soaked in sulfuric acid solution, and then washed to obtain a proton exchange membrane.

[0040] Further specifying, in (1), the solvent is dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone.

[0041] The beneficial effects of this invention are as follows: (1) The present invention prepares a sulfonated main chain ether-free polymer material, and uses the material to prepare a polyaromatic proton exchange membrane. By introducing sulfonic acid groups through substitution-oxidation method, the oxidation stability of the proton exchange membrane material is improved while maintaining its proton conductivity and dimensional stability.

[0042] (2) This invention uses aromatic monomers and 3,5-difluorotrifluoroacetophenone as raw materials and employs a superacid-catalyzed Friedel-Crafts hydroxyalkylation reaction to prepare fluorinated precursor polymers PDPtf and PTPtf. These two polymers are also fluorinated aromatic polymers. Then, sulfonic acid groups are precisely introduced onto the fluorinated aromatic polymers through a nucleophilic substitution-post-sulfonation method, successfully preparing monosulfonated fluorinated sulfonic acid polymers and disulfonated fluorinated sulfonic acid polymers. Specifically, the first step is a substitution reaction. In the first substitution reaction of the mono / disulfonated fluorinated sulfonic acid polymers, under the premise of fixed substitution reaction time and raw material feed ratio... By controlling the temperature, the degree of thiolization and substitution sites of the polymer can be precisely controlled. Specifically, the amount of sodium hydrosulfide is determined according to the polymer with a specific degree of sulfonation. For example, to prepare a polymer with 50% sulfonation, the required reactants are calculated, and the amount of sodium hydrosulfide is controlled to be 2.5 times the calculated feed ratio. The degree of sulfonation is mainly controlled by changing the reaction temperature, because different degrees of sulfonation require different reaction temperatures. Therefore, for the same fluorinated precursor polymer, different degrees of substitution can be obtained by adjusting the temperature under the condition of fixed sodium hydrosulfide amount. Subsequently, in the first oxidation reaction of the mono / dual sulfonated fluorosulfonic acid polymers, the thiol groups are converted into sulfonic acid groups through oxidation by a hydrogen peroxide / mixed acid system, thereby preparing polyaromatic hydrocarbons with clear sulfonation sites and high sulfonation. This provides a new route for the synthesis of monobenzene ring disulfonic acid type (also known as disulfonated fluorosulfonic acid polymer) polyaromatic proton exchange membrane materials with a main chain without quaternary carbon structure. Furthermore, in the second substitution and oxidation reaction of the double-sulfonated fluorosulfonic acid polymer, the above-mentioned characteristics are also present: under the premise of fixed reaction time and raw material feed ratio, the degree of thiolization substitution and substitution site of the polymer can be precisely controlled by adjusting the temperature; subsequently, through oxidation by hydrogen peroxide / mixed acid system, the thiol group is converted into sulfonic acid group, thereby preparing polyaromatic hydrocarbons with clear sulfonation sites and high sulfonation degree.

[0043] (3) The hydrophobic fluorinated benzene ring side group and the hydrophilic sulfonic acid group of the polyaromatic proton exchange membrane of the present invention have a polarity difference, but the polarity difference between them and the hydrophilic disulfonic acid group is greater, which is more conducive to the formation of microphase separation structure and the construction of continuous proton transport channels. At the same time, the hydrophobic fluorinated segment effectively inhibits the swelling rate of the membrane and improves its dimensional stability. (4) The fluorinated precursor polymer of the present invention is simple to synthesize. The polymer with monobenzene monosulfonic acid group and monobenzene disulfonic acid can be prepared by controlling the reaction temperature and time.

[0044] (5) Using the polyaromatic proton exchange membrane of the present invention can effectively improve the oxidative stability of the membrane material, maintain good proton conductivity and improve the dimensional stability of the membrane material. Among them, the monobenzene disulfonic acid type polyaromatic proton exchange membrane is better than the monobenzene monosulfonic acid type polyaromatic proton exchange membrane (also known as monosulfonated fluorinated sulfonic acid polymer). Attached Figure Description

[0045] Figure 1 The 1H NMR spectrum of PTPtf prepared in Example 1 (solvent: DMSO-d6); Figure 2 The nuclear magnetic resonance fluorine spectra of the fluorosulfonic acid polymers prepared in Examples 1-12 (solvent: DMSO-d6). Figure 3 The results of water absorption and swelling tests of the proton exchange membranes prepared in Examples 1-12 are shown in (a) water absorption test and (b) swelling test. Figure 4 The conductivity test results are for the proton exchange membranes prepared in Examples 1-12; Figure 5 The battery performance test results are for the proton exchange membrane prepared in Example 10. Detailed Implementation

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0047] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0048] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0050] The synthesis route of PTPtf in the following examples is as follows:

[0051] The synthetic route for PDPtf is as follows:

[0052] Example 1 (1) Synthesis of fluorine-containing precursor polymer PTPtf 0.02 mol (3.084 g) of terphenyl, 1-(3,5-difluorophenyl)-2,2,2-trifluoropropanone (0.024 mol, 7.440 g) and 20 mL of dichloromethane were added to a 100 mL round-bottom flask at 0 °C and stirred for 10 min. Then, 30 mL of trifluoromethanesulfonic acid was slowly added dropwise. The reaction was carried out at room temperature (20-30 °C) for 2 h. The resulting purple viscous solution was slowly precipitated into anhydrous ethanol, washed several times with deionized water, purified using a Soxhlet extractor (methanol as solvent), and dried under vacuum at 90 °C for 24 h to obtain the white target product PTPtf, yield: 99%, viscosity: 1.35 dL / g. The 1H NMR spectrum of PTPtf is shown below. Figure 1 As shown; (2) Synthesis of monosulfonated fluorosulfonic acid polymer (SPTPtf-25%) (a) Dissolve 3g of PTPtf in DMF (40mL) at 25℃, add sodium hydrosulfide (0.77g, 0.008mol) under nitrogen, heat to 80℃ and react for 10h. Slowly precipitate the resulting green polymer solution into deionized water, wash three times with deionized water, purify with a Soxhlet extractor (methanol as solvent), and dry under vacuum at 100℃ for 24h to obtain substituted product 1. (b) Add substitution product 1 (2g), glacial acetic acid (6mL), concentrated sulfuric acid (1mL), hydrogen peroxide (4mL) and deionized water (2mL) to a 50mL round-bottom flask. After reacting at room temperature for 24h, filter the solid and wash it three times with deionized water until neutral. Then dry it under vacuum at 90℃ for 24h to obtain the pale yellow target product SPTPtf-25% (25% represents x), y is 0.75, and the structure is shown in Formula I. The structure of Ar1 is Formula IV, and the viscosity is 1.29dL / g. (3) Preparation of proton exchange membrane: 1g SPTPtf-25% was dissolved in 20mL dimethyl sulfoxide to prepare a casting solution with a concentration of 5 wt%. After filtration and defoaming treatment, the casting solution was cast onto a glass plate to form a membrane. The membrane was then placed in a 75℃ oven and heated for 24h, and then transferred to a 100℃ vacuum oven to dry for 12h. The dried homogeneous membrane was soaked in deionized water for 24h and then soaked in 2M H2SO4 solution for 2 days. After washing with deionized water multiple times, the proton exchange membrane was obtained and stored in deionized water for later use.

[0053] Example 2 The difference between this embodiment and Example 1 is that: (a) sodium hydrosulfide is 1.078 g (0.011 mol), and the temperature is raised to 90°C; (b) glacial acetic acid is 8 mL, concentrated sulfuric acid is 1.5 mL, hydrogen peroxide is 5 mL, and deionized water is 3 mL, to obtain SPTPtf-35%, y is 0.65, and the structure is as shown in Formula I, where Ar1 has the structure of Formula IV, and the viscosity is 1.16 dL / g; (3) SPTPtf-25% is replaced with SPTPtf-35%, and the remaining process steps and parameter settings are the same as in Example 1.

[0054] Example 3 The difference between this embodiment and Example 1 is that: (a) sodium hydrosulfide is 1.232 g (0.013 mol) and the temperature is raised to 100℃; (b) glacial acetic acid is 10 mL, concentrated sulfuric acid is 2 mL, hydrogen peroxide is 6 mL, and deionized water is 4 mL to obtain SPTPtf-40%, y is 0.6, and the structure is as shown in Formula I, wherein the structure of Ar1 is Formula IV, and the viscosity is 1.16 dL / g; (3) SPTPtf-25% is replaced with SPTPtf-40%, and the remaining process steps and parameter settings are the same as in Example 1.

[0055] Example 4 The difference between this embodiment and Example 1 is that: (a) sodium hydrosulfide is 1.540g (0.016mol) and the temperature is raised to 120℃; (b) glacial acetic acid is 12mL, concentrated sulfuric acid is 2mL, hydrogen peroxide is 8mL, and deionized water is 4mL to obtain SPTPtf-50%, y is 0.5, and the structure is as shown in Formula I, wherein the structure of Ar1 is Formula IV, and the viscosity is 0.97dL / g; (3) SPTPtf-25% is replaced with SPTPtf-50%, and the remaining process steps and parameter settings are the same as in Example 1.

[0056] Example 5 The difference between this embodiment and Example 1 is that: (1) terphenyl is replaced with biphenyl, the amount is 0.02mol (4.606g), and the fluorinated precursor polymer obtained is PDPtf; (2) in step (a) PTPtf is replaced with PDPtf, sodium hydrosulfide is 0.660g (0.007mol), SPDPtf-25% is obtained, y is 0.75, the structure is as shown in Formula I, where Ar1 has the structure of Formula III, viscosity: 1.22dL / g; (3) SPTPtf-25% is replaced with SPDPtf-25%, and the remaining process steps and parameter settings are the same as in Example 1.

[0057] Example 6 The difference between this embodiment and Example 2 is that: (1) terphenyl is replaced with biphenyl, and the amount is 0.02 mol (4.606 g), and the fluorinated precursor polymer is PDPtf; (2) in step (a), PTPtf is replaced with PDPtf, and sodium hydrosulfide is 0.927 g (0.009 mol), and SPDPtf-35% is obtained, with y being 0.65, and the structure is as shown in Formula I, where Ar1 has the structure of Formula III, and the viscosity is 1.12 dL / g; (3) SPTPtf-35% is replaced with SPDPtf-35%, and the remaining process steps and parameter settings are the same as in Example 1.

[0058] Example 7 The difference between this embodiment and Example 3 is that: (1) terphenyl is replaced with biphenyl, the amount is 0.02mol (4.606g), and the fluorinated precursor polymer obtained is PDPtf; (2) in step (a) PTPtf is replaced with PDPtf, sodium hydrosulfide is 1.059g (0.011mol), SPDPtf-40% is obtained, y is 0.6, the structure is as shown in Formula I, where Ar1 has the structure of Formula III, viscosity: 1.05dL / g; (3) SPTPtf-40% is replaced with SPDPtf-40%, and the remaining process steps and parameter settings are the same as in Example 1.

[0059] Example 8 The difference between this embodiment and embodiment 4 is that: (1) biphenyl is replaced with terphenyl, the amount is 0.02 mol (4.606 g), and the fluorinated precursor polymer is PDPtf; (2) in step (a) PTPtf is replaced with PDPtf, sodium hydrosulfide is 1.324 g (0.013 mol), SPDPtf-50% is obtained, y is 0.5, the structure is as shown in formula I, where Ar1 has the structure of formula III, viscosity: 0.96 dL / g; (3) SPTPtf-50% is replaced with SPDPtf-50%, and the remaining process steps and parameter settings are the same as in embodiment 1.

[0060] Example 9 (1) Synthesis of the fluorinated precursor polymer PTPtf: Same as step (1) in Example 1; (2) Synthesis of monosulfonated fluorosulfonic acid polymer (SPTPtf-25%): Same as step (2) in Example 1; (3) Synthesis of bisulfonated fluorosulfonic acid polymer (BisPTPtf-50%) (a) Dissolve 3g of SPTPtf-25% in DMF (40mL) at 25℃, add sodium hydrosulfide (0.77g, 0.008mol), react at 25℃ for 12h, slowly precipitate the resulting green polymer solution into deionized water, wash three times with deionized water, then purify with a Soxhlet extractor (methanol as solvent), and vacuum dry at 100℃ for 24h to obtain substituted product 2; (b) The substituted product 2 (2g), glacial acetic acid (6mL), concentrated sulfuric acid (1mL), hydrogen peroxide (4mL) and deionized water (2mL) were added to a 50mL round-bottom flask. After reacting at room temperature for 40h, the solid was filtered and washed three times with deionized water until neutral. Then it was dried under vacuum at 90℃ for 24h to obtain the pale yellow target product BisPTPtf-50%, y=0.5, with the structure shown in Formula II, wherein Ar1 has the structure of Formula IV, and the viscosity is 0.87dL / g. (4) Preparation of proton exchange membrane: 1g BisPTPtf-50% was dissolved in 20mL of dimethyl sulfoxide to prepare a casting solution with a concentration of 5wt%. After filtration and defoaming treatment, the casting solution was cast onto a glass plate to form a membrane. The membrane was then placed in a 75℃ oven and heated for 24h, and then transferred to a 100℃ vacuum oven to dry for 12h. The dried homogeneous membrane was soaked in deionized water for 24h and then soaked in 2M H2SO4 solution for 2 days. After washing with deionized water multiple times, the proton exchange membrane was obtained and stored in deionized water for later use.

[0061] Example 10 The difference between this embodiment and embodiment 9 is that: in step (a) of (3), SPTPtf-25% is replaced with SPTPtf-35%, and sodium hydrosulfide is 1.078g (0.011mol); in (b), glacial acetic acid is 8mL, concentrated sulfuric acid is 1.5mL, hydrogen peroxide is 5mL, and deionized water is 3mL, to obtain BisPTPtf-70%, y is 0.3, and the structure is as shown in formula II, wherein the structure of Ar1 is formula IV, and the viscosity is 0.85dL / g; in (4), BisPTPtf-50% is replaced with BisPTPtf-70%, and the remaining process steps and parameter settings are the same as in embodiment 9.

[0062] Example 11 The difference between this embodiment and embodiment 9 is that: in step (a) of (3), SPTPtf-25% is replaced with SPDPtf-25%, sodium hydrosulfide is 0.660g (0.007mol), BisPDPtf-50% is obtained, y is 0.5, and the structure is as shown in formula II, wherein the structure of Ar1 is formula III, and the viscosity is 0.74dL / g; in (4), BisPTPtf-50% is replaced with BisPDPtf-50%, and the structure is as shown in formula II. The remaining process steps and parameter settings are the same as in embodiment 9.

[0063] Example 12 The difference between this embodiment and embodiment 10 is that: in step (a) of (3), SPTPtf-35% is replaced with SPDPtf-35%, sodium hydrosulfide is 0.927g (0.009mol), BisPDPtf-70% is obtained, y is 0.3, and the structure is as shown in formula II, wherein the structure of Ar1 is formula III, and the viscosity is 0.74dL / g; in (4), BisPTPtf-70% is replaced with BisPDPtf-70%, and the remaining process steps and parameter settings are the same as in embodiment 10.

[0064] Polymer characterization and performance testing (a) Nuclear magnetic resonance fluorine spectrum of polyaromatic hydrocarbons The NMR fluorine spectra (solvent: DMSO-d6) of the fluorosulfonic acid polymers (polyaromatics) prepared in Examples 1-12 are as follows: Figure 2 As shown.

[0065] (ii) Water absorption and swelling rate Figure 3 The results show the water absorption and swelling rate of the proton exchange membranes prepared in Examples 1-12. It can be seen that compared to the SPTPtf-50% membrane with the same IEC value, the proton exchange membrane with disulfonic acid side chains, such as BisPTPtf-50%, has a lower water absorption and swelling rate due to the more concentrated distribution of ionic groups and a higher proportion of hydrophobic segments. The introduction of fluorinated segments not only promotes the separation of the hydrophilic / hydrophobic microphases but also effectively reduces the swelling rate of the proton exchange membrane. This is attributed to the fact that the hydrophobicity of the fluorinated segments reduces the membrane's interaction with water molecules and simultaneously enhances intermolecular forces, thereby reducing the swelling rate of the polymer membrane in an aqueous environment. (iii) Electrical conductivity Figure 4 The results show the conductivity of the proton exchange membranes prepared in Examples 1-12. It can be seen that the disulfonic acid groups are tightly arranged through intermolecular forces, forming a more continuous hydrophilic region and constructing a highly efficient proton transport channel, thereby improving proton transport efficiency. The disulfonated polymer membrane exhibits higher conductivity.

[0066] (iv) Battery performance The performance evaluation of the hydrogen-oxygen fuel cell was conducted using a fuel cell testing system. The membrane electrode assembly (MEA) was prepared as follows: a platinum-carbon catalyst (Pt / C, with a platinum mass fraction of 60%) and a Nafion binder (15 wt% Nafion content, mixed with water and isopropanol in a 1:3 ratio to obtain a highly dispersed binder) were ultrasonically dispersed. The catalyst was uniformly sprayed onto both sides of the membrane sample using a spraying method, and the MEA was prepared by hot pressing, controlling the platinum loading at 0.5 mg / cm³. -2 The effective spraying area is 3cm × 3cm. The fuel cell experiment was conducted at 80℃ (100% relative humidity), with hydrogen and air flow rates of 1L / min. -1 and 0.5L min -1 No external back pressure was applied. Voltage and current density were recorded at fixed time intervals during the test.

[0067] Figure 5 Battery performance test results for commercial Nafion 212 membrane and the proton exchange membrane prepared in Example 10. It can be seen that the maximum peak power density of the membrane in Example 10 is 694 mW / cm². -2 It has approximately twice the voltage of commercial Nafion 212 membranes and an open-circuit voltage of 0.96V, demonstrating excellent hydrogen barrier performance.

[0068] (v) Mechanical properties Table 1 shows the mechanical property test results of the proton exchange membranes prepared in Examples 1-12. It can be seen that most sulfonated polymer proton exchange membranes have good tensile strength (generally ≥12.5MPa), with the highest reaching 51.6MPa, indicating that the post-sulfonation of high molecular weight fluorinated precursor polymers can meet the application requirements of proton exchange membranes for mechanical properties.

[0069] Table 1

[0070] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A polyaromatic hydrocarbon for preparing proton exchange membranes, characterized in that, The polyaromatic hydrocarbon is a monosulfonated fluorosulfonic acid polymer or a disulfonated fluorosulfonic acid polymer. The structure of the monosulfonated fluorosulfonic acid polymer is shown in Formula I, and the structure of the disulfonated fluorosulfonic acid polymer is shown in Formula II. Formula I, Formula II, Where x > 0, y ≥ 0, and y:x = (0-1):(0.7-0.1), the structure of Ar1 is shown in Equation III or Equation IV: Formula III, Formula IV.

2. A method for preparing the polyaromatic hydrocarbon according to claim 1, characterized in that, The preparation method includes: (1) Synthesis of fluorinated precursor polymer: Aromatic monomers and 3,5-difluorotrifluoroacetophenone were dissolved in a solvent at 0℃, and trifluoromethanesulfonic acid was added dropwise after stirring to carry out the reaction. The mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain the fluorinated precursor polymer. (2) Synthesis of substitution product 1: The fluorine-containing precursor polymer was dissolved in a solvent and sodium hydrosulfide was introduced under a nitrogen atmosphere to obtain a reaction system. The substitution reaction was carried out, and the mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain substitution product 1. (3) Synthesis of polyaromatic hydrocarbons: Substitution product 1, glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water are mixed and oxidized. The mixture after the reaction is filtered, washed and vacuum dried to obtain polyaromatic hydrocarbons with the structure shown in Formula I.

3. A method for preparing the polyaromatic hydrocarbon according to claim 1, characterized in that, (1) Synthesis of fluorinated precursor polymer: Aromatic monomers and 3,5-difluorotrifluoroacetophenone were dissolved in a solvent at 0℃, and trifluoromethanesulfonic acid was added dropwise after stirring. The reaction was carried out at room temperature for 2 hours. The mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain the fluorinated precursor polymer. (2) Synthesis of substitution product 1: The fluorine-containing precursor polymer was dissolved in a solvent, and sodium hydrosulfide was introduced under a nitrogen atmosphere to carry out the substitution reaction. The mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain substitution product 1. (3) Synthesis of monosulfonated fluorosulfonic acid polymer: Substitution product 1, glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water are mixed and oxidized. The mixture after reaction is filtered, washed and vacuum dried to obtain monosulfonated fluorosulfonic acid polymer. (4) Synthesis of substitution product 2: The monosulfonated fluorosulfonic acid polymer was dissolved in a solvent and sodium hydrosulfide was added under a nitrogen atmosphere to carry out the substitution reaction. The mixture after the reaction was precipitated, washed, purified and vacuum dried to obtain substitution product 2. (5) Synthesis of polyaromatic hydrocarbons: The substituted product 2, glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water were mixed and oxidized. The mixture after the reaction was filtered, washed and vacuum dried to obtain polyaromatic hydrocarbons with the structure shown in Formula II.

4. The preparation method according to claim 2 or 3, characterized in that, (1) The aromatic monomer is terphenyl or biphenyl, the molar ratio of the aromatic monomer to 3,5-difluorotrifluoroacetophenone is 1:(1.05-1.2), and the molar ratio of the aromatic monomer to trifluoromethanesulfonic acid is 1:(1-1.5).

5. The preparation method according to claim 2 or 3, characterized in that, (2) The molar ratio of sodium hydrosulfide to fluorine-containing precursor polymer is (1.5-4):1; the substitution reaction temperature is 50-150℃ and the time is 8-20h; the solid content of the reaction system is 5-20%.

6. The preparation method according to claim 2 or 3, characterized in that, (3) The mass-volume ratio of the substituted product 1 to glacial acetic acid, concentrated sulfuric acid, hydrogen peroxide and deionized water is 1g: (3-13)mL: (0.5-5)mL: (2-4)mL: (1-5)mL; the oxidation reaction temperature is 20-40℃ and the time is 20-40h.

7. The preparation method according to claim 3, characterized in that, (4) The molar ratio of sodium hydrosulfide to monosulfonated fluorosulfonic acid polymer is (1.5-4):1; the substitution reaction temperature is 20-40℃ and the time is 10-20h; the solid content of the reaction system is 5-20%; (5) The oxidation reaction temperature is 20-40℃ and the time is 20-50h.

8. A proton exchange membrane, characterized in that, The polyaromatic hydrocarbon described in claim 1 is used as the film-forming raw material.

9. A method for preparing the proton exchange membrane according to claim 8, characterized in that, The preparation method includes the following steps: (1) Dissolve polyaromatic hydrocarbons in a solvent to obtain a casting solution, cast the casting solution onto a glass plate to form a film, and dry it to obtain a homogeneous film; (2) The homogeneous membrane is first soaked in water, then soaked in sulfuric acid solution, and then washed to obtain a proton exchange membrane.

10. An application of the proton exchange membrane according to claim 8, characterized in that, It is used as a membrane material for fuel cells.

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