Sulfonated polyethersulfone proton exchange membrane and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and particularly discloses a sulfonated polyethersulfone proton exchange membrane and a preparation method thereof. The method comprises the following steps: co-dissolving sulfonated polyethersulfone and aniline in a DMF (N, N-dimethylformamide) / alcohol mixed solvent to form a film, enriching aniline through vacuum evaporation, carrying out acid treatment and ammonium persulfate oxidation in-situ polymerization to generate polyaniline, and finally carrying out heat treatment to obtain a finished product. According to the method, the proton conductivity of the membrane can be remarkably improved under the condition of low sulfonation degree, and meanwhile, good mechanical strength and dimensional stability are kept.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer materials, and particularly relates to a sulfonated polyether sulfone proton exchange membrane and a preparation method thereof. BACKGROUND

[0002] The proton exchange membrane is a core component of electrochemical devices such as a vanadium redox flow battery, and its performance directly determines the efficiency and service life of the battery. Sulfonated polyether sulfone (SPES) is considered as one of the ideal materials to replace traditional perfluorosulfonic acid membranes (such as Nafion membranes) due to its high strength, low cost and environmental friendliness. The sulfonic acid groups in the SPES molecule can form hydrophilic channels to provide a path for proton transport.

[0003] However, SPES-based proton exchange membranes face a key challenge: it is difficult to balance the proton conductivity and dimensional stability of the membrane. When the sulfonation degree is too high, the water absorption of the membrane is too large, and excessive swelling easily occurs, resulting in a significant decrease in mechanical strength; when the sulfonation degree is too low, the number of sulfonic acid groups is insufficient, and it is difficult to form a continuous proton transport channel, resulting in too low proton conductivity.

[0004] Polyaniline (PANI) is studied for modifying proton exchange membranes to improve proton conductivity due to its good chemical stability and protonation characteristics. However, how to uniformly introduce polyaniline into the SPES matrix to effectively improve the proton conductivity without significantly sacrificing its mechanical properties is still a technical problem to be solved.

[0005] Therefore, it is of great significance to develop a preparation method of SPES composite membrane that can simultaneously have high proton conductivity and good stability at a low sulfonation degree. SUMMARY

[0006] The purpose of the embodiments of the present application is to provide a sulfonated polyether sulfone proton exchange membrane and a preparation method thereof, which co-dissolve sulfonated polyether sulfone and aniline in a DMF / alcohol mixed solvent to form a film, enrich aniline by vacuum evaporation, generate polyaniline in situ by acid treatment and ammonium persulfate oxidation, and finally obtain the finished product by heat treatment, thereby significantly improving the proton conductivity of the membrane at a low sulfonation degree, while maintaining good mechanical strength and dimensional stability, thereby solving at least one technical problem involved in the background art.

[0007] To solve the above technical problems, the present application is implemented as follows: The embodiments of the present application provide a preparation method of a sulfonated polyether sulfone proton exchange membrane, comprising the following steps: Step S1, dissolving sulfonated polyether sulfone and aniline in a mixed solution of N,N-dimethylformamide (DMF) and an alcohol substance to obtain a uniform casting solution; using a doctor blade to cast the uniform casting solution into a film; Step S2, vacuum evaporation of the film at 30-50℃ for 1-5 hours; Step S3, ultrasonic treatment of the vacuum-evaporated film in an acid solution with a concentration of 1-3 mol / L for 20-60 minutes; Step S4, addition of an ammonium persulfate solution with a concentration of 2-5 mol / L, continued ultrasonic treatment for 5-10 minutes, and then static immersion for 18-36 hours; multiple washing of the mixture with water and ethanol to obtain a sulfonated polyether sulfone film material; Step S5, heat treatment of the sulfonated polyether sulfone film material at 110-140℃ for 2-6 hours to obtain a finished proton exchange membrane.

[0008] Optionally, in step S1, the sulfonation degree of the sulfonated polyether sulfone is 10%-30%.

[0009] Optionally, in step S1, the alcohol is one of methanol, ethanol, or propanol.

[0010] Optionally, in step S1, the content of each component in the casting solution is, by mass fraction: sulfonated polyether sulfone 12-17 parts; aniline 1-3 parts; N,N-dimethylformamide 65-81 parts; alcohol 6-15 parts.

[0011] Optionally, in step S3, the acid solution is hydrochloric acid or sulfuric acid.

[0012] Optionally, in step S4, the static immersion time is 18-36 hours.

[0013] The application also provides a sulfonated polyether sulfone proton exchange membrane prepared by the preparation method.

[0014] Compared with the prior art, the application has the following beneficial effects: (1) significantly improved proton conductivity: vacuum evaporation guides the directional enrichment of aniline, and the in-situ polymerization of a high-conductivity polyaniline network is generated in the film by the synergistic action of acid and oxidant, providing a large number of additional proton transport sites, thereby achieving a substantial increase in proton conductivity (up to 77.5 mS / cm in Example 1) at a lower sulfonation degree (10%-30%).

[0015] (2) excellent mechanical properties and dimensional stability: the in-situ generation of polyaniline does not destroy the bulk structure of the sulfonated polyether sulfone, and the film material still maintains a relatively high tensile strength (transverse > 56 MPa, longitudinal > 70 MPa). At the same time, the lower sulfonation degree and the heat treatment process effectively inhibit the excessive swelling of the film in water, and the dimensional change rate is significantly lower than that of the comparative example (<3.8% vs. >4.3%).

[0016] (3) Strong process synergy, stable effect: the method combines solvent selection, vacuum evaporation, in-situ polymerization and heat treatment process, and the parameters of each step synergize to successfully solve the contradiction between high proton conductivity and high stability in traditional methods, and the process is controllable and has good repeatability.

[0017] (4) Low cost, environmentally friendly: the raw materials used, sulfonated polyether sulfone and aniline, are relatively low in price, and the use of expensive perfluorosulfonic acid materials is avoided, reducing production costs and making it more commercially viable. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the following embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor based on these drawings. Figure 1 A flowchart of the preparation method of the sulfonated polyether sulfone proton exchange membrane provided by the present application. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0020] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of a kind and are not limited to the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / ", generally indicates that the objects before and after are in an "or" relationship.

[0021] Please refer to Figure 1 As shown in the drawings, the embodiment of the present application provides a preparation method of a sulfonated polyether sulfone proton exchange membrane, comprising the following steps: Step S1, dissolving sulfonated polyether sulfone and aniline in a mixed solution of N,N-dimethylformamide and an alcohol substance to obtain a uniform casting solution; using a doctor blade to cast the uniform casting solution into a film; Step S2, vacuum evaporation of the film at 30-50℃ for 1-5 hours; Step S3, ultrasonic treatment of the vacuum-evaporated film in an acid solution with a concentration of 1-3 mol / L for 20-60 minutes; Step S4, addition of an ammonium persulfate solution with a concentration of 2-5 mol / L, continued ultrasonic treatment for 5-10 minutes, and then static immersion for 18-36 hours; multiple washing of the mixture with water and ethanol to obtain a sulfonated polyether sulfone film material; Step S5, heat treatment of the sulfonated polyether sulfone film material at 110-140℃ for 2-6 hours to obtain a finished proton exchange membrane.

[0022] In step S1, the sulfonation degree of the sulfonated polyether sulfone is 10%-30%.

[0023] The alcohol is one of methanol, ethanol, or propanol.

[0024] In the casting solution, the content of each component is as follows in mass fraction: Sulfonated polyether sulfone 12-17 parts; Aniline 1-3 parts; N,N-dimethylformamide 65-81 parts; Alcohol 6-15 parts.

[0025] In step S2, during the vacuum evaporation process, the alcohol with a lower boiling point is preferentially volatilized, guiding the migration and enrichment of aniline molecules to the film surface, and laying a foundation for subsequent in-situ polymerization.

[0026] In step S3, the acid solution is hydrochloric acid or sulfuric acid, and through acid treatment, aniline molecules are protonated to form aniline salt, and ultrasonic treatment helps the acid to penetrate into the film.

[0027] In step S4, the static immersion time is 18-36 hours, allowing aniline to be fully in-situ polymerized to form polyaniline (PANI). After the reaction is completed, the film material is repeatedly washed with deionized water and anhydrous ethanol until the washing liquid is neutral, so as to remove residual reactants and by-products, and obtain an SPES / PANI composite film material.

[0028] Further explanation is needed for step S5, that is, after heat treatment, it is helpful to remove trace amounts of residual solvents and water in the film, further improve the dimensional stability and mechanical strength of the film, and obtain the final sulfonated polyether sulfone proton exchange membrane product.

[0029] The application also provides a sulfonated polyether sulfone proton exchange membrane prepared by the preparation method.

[0030] The preparation method of the sulfonated polyether sulfone proton exchange membrane provided by the present application is described in detail below with specific examples and comparative examples.

[0031] Example 1 SPES with a sulfonation degree of 20% 15 g, aniline 2 g, DMF 70 g, and ethanol 13 g were weighed and mixed and stirred until completely dissolved to obtain a uniform casting solution. The casting solution was cast on a glass plate using a doctor blade, and the wet film was placed in a vacuum drying oven at 40°C for 2 hours. The film was immersed in a 1 mol / L sulfuric acid solution and ultrasonically treated for 30 minutes. A 3 mol / L ammonium persulfate solution was added, and ultrasonic treatment was continued for 6 minutes, followed by standing and immersion for 24 hours. After the reaction was completed, the film was repeatedly washed with water and ethanol until it was neutral. The resulting film was heat treated at 120°C for 3 hours to obtain a finished proton exchange membrane.

[0032] Example 2 SPES with a sulfonation degree of 10% 15 g, aniline 3 g, DMF 67 g, and ethanol 15 g were weighed and cast into a film according to the method described in Example 1. The vacuum evaporation conditions were 50°C for 3 hours. The acid treatment used 2 mol / L sulfuric acid and ultrasonic treatment for 60 minutes. The polymerization used 4 mol / L ammonium persulfate and ultrasonic treatment for 10 minutes, followed by standing and immersion for 30 hours. The heat treatment conditions were 120°C for 3 hours to obtain a finished proton exchange membrane.

[0033] Example 3 SPES with a sulfonation degree of 30% 15 g, aniline 1 g, DMF 74 g, and ethanol 8 g were weighed and cast into a film according to the method described in Example 1. The vacuum evaporation conditions were 30°C for 3 hours. The acid treatment used 1 mol / L sulfuric acid and ultrasonic treatment for 30 minutes. The polymerization used 2 mol / L ammonium persulfate and ultrasonic treatment for 10 minutes, followed by standing and immersion for 18 hours. The heat treatment conditions were 120°C for 3 hours to obtain a finished proton exchange membrane.

[0034] Example 4 SPES with a sulfonation degree of 20% 17 g, aniline 3 g, DMF 65 g, and ethanol 15 g were weighed and cast into a film according to the method described in Example 1. The vacuum evaporation conditions were 40°C for 2 hours. The acid treatment used 3 mol / L sulfuric acid and ultrasonic treatment for 30 minutes. The polymerization used 4 mol / L ammonium persulfate and ultrasonic treatment for 10 minutes, followed by standing and immersion for 30 hours. The heat treatment conditions were 130°C for 4 hours to obtain a finished proton exchange membrane.

[0035] Example 5 Take SPES 13 g, aniline 1 g, DMF 79 g, ethanol 7 g with sulfonation degree of 20%, and prepare a film according to the method described in Example 1. The vacuum evaporation condition is 30℃ for 3 hours. The acid treatment uses 1 mol / L sulfuric acid for 30 minutes of ultrasonic treatment. The polymerization uses 2 mol / L ammonium persulfate for 10 minutes of ultrasonic treatment, and the standing soaking is 30 hours. The heat treatment condition is 130℃ for 4 hours, and the finished proton exchange membrane is obtained.

[0036] Comparative Example 1 Without adding aniline, take SPES 17 g, DMF 70 g, ethanol 13 g with sulfonation degree of 20%, and prepare a film, evaporate, acid soak (without adding oxidant), wash and heat treat according to the same steps in Example 1, and the finished proton exchange membrane is obtained.

[0037] Comparative Example 2 Add aniline, but only use standing soaking (without ultrasonic treatment) in the acid treatment step, and do not add ammonium persulfate for polymerization. Specifically, take SPES 15 g, aniline 2 g, DMF 70 g, ethanol 13 g, and after film preparation and vacuum evaporation, directly soak in 1 mol / L sulfuric acid for 24 hours, and then wash, heat treat, and the finished proton exchange membrane is obtained.

[0038] Performance Test The films prepared in Examples 1-5 and Comparative Examples 1-2 above are tested for performance, and the results are shown in Table 1.

[0039] Table 1 Test data of the prepared proton exchange membranes of Examples 1-5 and Comparative Examples 1-2 The test results show that the proton exchange membrane prepared by the method of the present application is significantly better than the comparative examples in terms of proton conductivity, dimensional stability and mechanical strength, effectively balancing the contradiction between high proton conductivity and good stability.

[0040] It should be noted that in this document, the terms "comprise", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed or inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "comprises a" does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0041] Furthermore, it is to be understood that the scope of the methods and systems of the present embodiments are not limited to what can be presently described and / or demonstrated. As such, the present embodiments are not to be limited to the specific illustrative situations and / or examples, but rather can be practiced with other like applications and / or in other like circumstances. Additionally, the features of certain examples can be combined with features of other examples.

[0042] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are merely illustrative, but are not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, and all belong to the protection of the present application.

Claims

1. A method for preparing a sulfonated polyethersulfone proton exchange membrane, characterized in that, Includes the following steps: Step S1: Dissolve sulfonated polyethersulfone and aniline in a mixed solution of N,N-dimethylformamide and alcohol to obtain a uniform casting solution; The uniform casting solution is scraped into a film using a scraper. Step S2: Vacuum evaporate the membrane at 30–50°C for 1–5 hours; Step S3: The membrane after vacuum evaporation is ultrasonically treated in an acid solution with a concentration of 1–3 mol / L for 20–60 minutes; Step S4: Add ammonium persulfate solution with a concentration of 2–5 mol / L, continue ultrasonic treatment for 5–10 minutes, and then let it stand for 18–36 hours; wash the mixture multiple times with water and ethanol to obtain sulfonated polyethersulfone membrane material. Step S5: Heat-treat the sulfonated polyethersulfone membrane material at 110–140°C for 2–6 hours to obtain a finished proton exchange membrane.

2. The preparation method according to claim 1, characterized in that, In step S1, the degree of sulfonation of the sulfonated polyether sulfone is 10%–30%.

3. The preparation method according to claim 1, characterized in that, In step S1, the alcohol is one of methanol, ethanol or propanol.

4. The preparation method according to claim 1, characterized in that, In step S1, the content of each component in the casting solution, by mass parts, is as follows: 12–17 parts of sulfonated polyethersulfone; 1–3 parts aniline; 65–81 parts of N,N-dimethylformamide; Alcohols: 6–15 parts.

5. The preparation method according to claim 1, characterized in that, In step S3, the acid solution is hydrochloric acid or sulfuric acid.

6. The preparation method according to claim 1, characterized in that, In step S4, the static soaking time is 18–36 hours.

7. A sulfonated polyethersulfone proton exchange membrane prepared by the preparation method according to any one of claims 1–6.

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