Alkaline anion exchange membrane containing double functional groups for synergistically improving swelling resistance and preparation method of alkaline anion exchange membrane

Abstract

The invention relates to the technical field of anion exchange membranes, in particular to a preparation method of an alkaline anion exchange membrane containing double functional groups for synergistically improving swelling resistance, which comprises the following steps: dissolving 5g of chloromethylated polyethersulfone in 100mL of N, N-dimethylformamide, adding 1.8 mmol of triethylamine and 1.8 mmol of benzimidazole, refluxing for 8 hours at 70 DEG C under the nitrogen protection condition, filtering, washing, and drying to obtain the alkaline anion exchange membrane containing double functional groups for synergistically improving swelling resistance. Stirring is performed once every 2 hours during the period; and cooling the reaction liquid to room temperature, pouring the reaction liquid into 50mL of ethanol for precipitation, filtering, washing with ethanol for 4 times, 20mL each time, and then carrying out vacuum drying at 60 DEG C for 6 hours to obtain the quaternary ammonium salt-benzimidazole modified polyethersulfone polymer. Quaternary ammonium salt serves as a core ion conduction site, and efficient transmission of OH <-> is guaranteed; benzimidazole can form multiple hydrogen bonds with quaternary ammonium salt and a membrane matrix to effectively restrain molecular chain movement of the membrane body and inhibit swelling of the membrane in an aqueous solution or a high-humidity environment, and meanwhile, benzimidazole can be used as an OH-relay station to promote rapid migration of ions in the membrane.

Description

Technical Field

[0001] This invention relates to the field of anion exchange membrane technology, and specifically to a method for preparing an alkaline anion exchange membrane containing bifunctional groups to synergistically enhance its anti-swelling properties. Background Technology

[0002] Anion exchange membranes are core functional components of energy conversion devices such as alkaline water electrolysis and alkaline fuel cells. Their performance directly determines the energy conversion efficiency, operational stability, and service life of the device. During the operation of these energy devices, the anion exchange membrane must simultaneously perform three key functions: firstly, as an ion transport channel, ensuring the absorption of OH- ions... - The advantages of anion exchange membranes include: efficient anion migration; serving as an electrode separator to prevent the mixing of reactants and ensure safe operation; and withstanding alkaline environments, specific temperature and humidity conditions to maintain long-term structural integrity and performance stability. However, existing anion exchange membrane technologies still have several performance bottlenecks, making it difficult to meet the application requirements of high-performance energy devices.

[0003] Current mainstream anion exchange membranes mostly rely on a single cationic group, such as quaternary ammonium salts, for ion conduction. This design easily leads to an inherent contradiction between ion conduction efficiency and swelling resistance: increasing the content of hydrophilic groups to improve ion conductivity significantly exacerbates the swelling of the membrane in aqueous solutions or high-humidity environments, resulting in membrane structural relaxation, decreased mechanical strength, and even membrane rupture; conversely, reducing hydrophilic groups to suppress swelling leads to insufficient ion transport channels, significantly sacrificing conduction efficiency. Furthermore, existing membrane materials generally lack sufficient alkali resistance. During long-term use in alkaline environments, quaternary ammonium salts and other cationic groups are prone to degradation reactions such as Hoffmann elimination and nucleophilic substitution, leading to a continuous reduction in ion conduction sites and a rapid decline in conductivity over time, failing to meet the long-term operation requirements of thousands of hours for the device.

[0004] Furthermore, existing anion exchange membranes suffer from severe limitations in adaptability to specific application scenarios. In high-temperature alkaline water electrolysis scenarios, such as at 90°C, existing membranes are prone to severe thermal swelling due to intensified molecular chain movement at high temperatures, disrupting the orderliness of ion conduction channels. The degradation rate of cation groups also accelerates significantly with increasing temperature, leading to a sharp decline in membrane performance. In low-humidity alkaline fuel cell scenarios, such as at 30% relative humidity, existing membranes have poor water retention capacity. Rapid water loss within the membrane under low humidity conditions easily leads to breakage of ion conduction channels, resulting in a significant reduction in conduction efficiency and the inability to maintain normal device discharge. Simultaneously, some processes for improving membrane performance have significant defects. Chemical crosslinking agents tend to remain in the membrane, potentially clogging ion conduction channels and affecting conduction efficiency. This also increases process steps and production costs, hindering large-scale industrial applications. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing an alkaline anion exchange membrane containing bifunctional groups to synergistically enhance its anti-swelling properties.

[0006] A further objective of this invention is to provide a method for preparing a basic anion exchange membrane containing bifunctional groups to synergistically enhance its anti-swelling properties, comprising the following steps:

[0007] (1) Functionalized grafting: Take 5g of chloromethylated polyethersulfone, dissolve it in 100mL of N,N-dimethylformamide, add 1.8mmol of triethylamine and 1.8mmol of benzimidazole, reflux at 70℃ for 8h under nitrogen protection, and stir once every 2h during the period;

[0008] (2) Post-treatment: After cooling the reaction solution of step (1) to room temperature, pour it into 50 mL of ethanol to precipitate. After filtration, wash with ethanol 4 times, 20 mL each time, and then dry under vacuum at 60 °C for 6 h to obtain quaternary ammonium salt-benzimidazole modified polyethersulfone polymer.

[0009] (3) Film formation: Quaternary ammonium salt-benzimidazole modified polyethersulfone film was prepared according to the general film formation procedure.

[0010] Preferably, in step (1), the molar ratio of triethylamine to benzimidazole is 1.2:0.8, the total molar amount is 3.6 mmol, and 0.5 g of dibromoethane is added at the same time. The molar ratio of dibromoethane to chloromethyl in chloromethylated polyethersulfone is 0.1:1. The reflux temperature is 75°C and the reflux time is 10 h. In step (2), the vacuum drying temperature is 65°C.

[0011] Preferably, the method further includes a blended substrate preparation step: 8g of polyethersulfone and 2g of sulfonated polyethersulfone are mixed and dissolved in 60mL of N,N-dimethylformamide. The mixture is stirred at 50°C for 4h until completely dissolved to obtain a polyethersulfone / sulfonated polyethersulfone blend. The blend is then subjected to chloromethylation treatment to obtain a blended chloromethylated polyethersulfone. In step (1), the chloromethylated polyethersulfone is replaced with the blended chloromethylated polyethersulfone, and 0.1g of hydroxylated silica is added during functionalization grafting. The mixture is ultrasonically dispersed for 40min and then refluxed for 9h.

[0012] Preferably, the sulfonated polyethersulfone has a sulfonation degree of 30%, and the chloromethyl content of the blended chloromethylated polyethersulfone is 1.7 mmol / g; the hydroxylated silica has a particle size of 50 nm and accounts for 2% of the mass of the blended chloromethylated polyethersulfone.

[0013] Preferably, the method also includes a step of preparing a fluorinated functional monomer: 0.3g of trifluoroethyl glycidyl ether and 0.1g of ethylenediamine are taken and stirred at 60°C for 2h to obtain a fluorinated amine monomer; in step (1), 0.05g of a fluorinated amine monomer and 0.05g of hydroxylated graphene oxide are added during functionalization grafting, and the mixture is ultrasonically dispersed for 60min and then refluxed at a temperature of 75°C for 12h; in step (2), the solvent used for precipitation is an ethanol-water mixture, the drying temperature is 70°C, and the drying time is 8h.

[0014] Preferably, the volume ratio of the ethanol-water mixture is 3:1; the particle size of the hydroxylated graphene oxide is 100 nm, and the fluorinated amine monomer and the hydroxylated graphene oxide each account for 1% of the mass of the blended chloromethylated polyethersulfone.

[0015] Preferably, in step (1), dibromoethane is not added. After obtaining the non-crosslinked bifunctional polymer, a pre-film with a thickness of 0.18 mm is prepared according to the general film-forming steps; it also includes a radiation crosslinking and nanocomposite step: the pre-film is immersed in an aqueous solution of nanocellulose, soaked at room temperature for 4 hours, and then taken out and used... 60 The product was irradiated with Co-γ rays at a dose of 20 kGy, followed by vacuum drying at 60°C for 6 hours.

[0016] Preferably, the concentration of the nanocellulose aqueous solution is 0.05 g / mL, and the length of the nanocellulose is 200 nm.

[0017] Preferably, the anion exchange membrane is prepared by the preparation method described in any one of claims 1-8, and the anion exchange membrane comprises quaternary ammonium salt groups, benzimidazole groups, and a polyethersulfone substrate.

[0018] Preferably, the anion exchange membrane is used in alkaline water electrolysis scenarios at 90°C or alkaline fuel cell scenarios with a relative humidity of 30%.

[0019] Compared with the prior art, the present invention has the following significant advantages:

[0020] 1. This invention constructs a dual-effect system of ion conduction and structural stability through the synergistic effect of quaternary ammonium salt and benzimidazole bifunctional groups. The quaternary ammonium salt serves as the core ion conduction site, ensuring the stability of OH groups. - Highly efficient transport; benzimidazole can form multiple hydrogen bonds with quaternary ammonium salts and the membrane matrix, effectively constraining the molecular chain movement of the membrane and inhibiting the swelling of the membrane in aqueous solutions or high humidity environments. Simultaneously, benzimidazole can act as an OH group... - The relay station promotes the rapid migration of ions within the membrane, fundamentally resolving the contradiction between ion conduction efficiency and swelling resistance in existing technologies.

[0021] 2. This invention introduces fluorine-containing side chains, utilizing the strong electronegativity and chemical stability of fluorine atoms to inhibit the degradation reaction of quaternary ammonium salts and other cationic groups in alkaline environments, thus slowing down the rate of group loss. At the same time, nano-components such as hydroxylated silica and hydroxylated graphene oxide can form stable interfacial interactions with the membrane substrate, enhancing the membrane structure's resistance to relaxation in alkaline environments, reducing the erosion of the membrane by alkaline solutions, significantly extending the membrane's service life, and ensuring that the membrane maintains high conductivity even after long-term use under alkaline conditions.

[0022] 3. For high-temperature alkaline water electrolysis scenarios, this invention constructs a sheet-like support structure using composite hydroxylated graphene oxide. Utilizing its high specific surface area and structural rigidity, it suppresses structural relaxation and swelling of the membrane at high temperatures. Combined with the alkali-resistant properties of the fluorinated side chains, it ensures stable membrane performance under high-temperature alkaline conditions. For low-humidity alkaline fuel cell scenarios, nanocellulose is introduced. Its abundant hydroxyl groups enhance the membrane's water retention capacity, maintain the integrity of ion conduction channels in low-humidity environments, and prevent a decrease in conduction efficiency due to water loss, enabling the membrane to precisely adapt to different operating conditions.

[0023] 4. This invention provides two enhancement methods: chemical crosslinking and radiation crosslinking. Chemical crosslinking introduces a crosslinking agent to construct a three-dimensional network structure, improving the mechanical strength of the membrane. Radiation crosslinking eliminates the need for chemical crosslinking agents, avoiding the impact of residual crosslinking agents on membrane performance, while also simplifying the preparation process and reducing production costs. Furthermore, by blending polyethersulfone with sulfonated polyethersulfone as a substrate, the hydrophilicity-hydrophobicity balance of the membrane can be flexibly adjusted, optimizing the membrane's processing performance and structural stability, thus facilitating industrial-scale production.

[0024] 5. The technical solution of this invention starts from a basic dual-functional system and gradually optimizes performance through cross-linking enhancement, substrate-nano synergy, and the introduction of scenario-based functional components. Each technical link is based on the extension of the preceding process, with strong process compatibility. The performance indicators of the membrane, such as anti-swelling, alkali resistance, and conductivity, can be flexibly adjusted and upgraded according to actual applications, laying a solid foundation for subsequent technology iteration and industrial application. Attached Figure Description

[0025] Figure 1 A schematic diagram of the time relationship curve of chemical crosslinking mentioned in this invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1:

[0028] This embodiment constructs a basic system with synergistic bifunctional groups, providing a reference for subsequent optimization:

[0029] Functionalization grafting: Take 5g of chloromethylated polyethersulfone prepared by the above general process, dissolve it in 100mL of N,N-dimethylformamide, add 1.8mmol of triethylamine as a quaternary ammonium salt source and 1.8mmol of benzimidazole as a rigid cooperating group, and reflux at 70℃ for 8h under nitrogen protection, stirring once every 2h to ensure uniform reaction.

[0030] Post-treatment: After the reaction solution was cooled to room temperature, it was poured into 50 mL of ethanol to precipitate the product. After filtration, it was washed four times with 20 mL of ethanol each time to remove unreacted triethylamine and benzimidazole. The product was then dried under vacuum at 60 °C for 6 h to obtain the quaternary ammonium salt-benzimidazole modified polyethersulfone polymer.

[0031] Film formation: A quaternary ammonium salt-benzimidazole modified polyethersulfone film, denoted as M1, was prepared according to the general film formation procedure.

[0032] The repeating unit chemical structure of chloromethylated polyethersulfone is shown in Formula 1 below:

[0033]

[0034] Based on the repeating unit [-O-C6H4-SO2-C6H4-]n of polyethersulfone (PES), chloromethyl groups (-CH2Cl) are introduced onto the benzene ring (usually a benzene ring connected to an oxygen atom) of polyethersulfone via a chloromethylation reaction to form chloromethylated polyethersulfone. Examples 1-5 all use this material as the substrate for functionalized grafting, and its chloromethyl groups provide reaction sites for subsequent grafting of quaternary ammonium salts and benzimidazole groups.

[0035] The repeating unit chemical structure of quaternary ammonium salt-benzimidazole modified polyethersulfone is shown in Formula 2 below:

[0036]

[0037] It is prepared by reacting chloromethylated polyethersulfone with triethylamine and benzimidazole; wherein, chloromethyl (-CH2Cl) reacts with triethylamine ((C2H5)3N) to generate a quaternary ammonium salt group (-CH2-N). + (C2H5)3Cl - The modified polymer serves as the core site for OH- conduction. Simultaneously, the chloromethyl group combines with the amino group (-NH-) of benzimidazole to graft benzimidazole onto the polyethersulfone backbone. The benzimidazole ring can interact with the quaternary ammonium salt and the polyethersulfone matrix through hydrogen bonds, thereby inhibiting membrane swelling. The M1 membrane in Example 1 and the M2 membrane in Example 2 both use this modified polymer as the core film-forming material.

[0038] Example 2:

[0039] This embodiment, based on the bifunctional system of Example 1, enhances ion conduction by adjusting the proportion of functional groups and introduces a crosslinking agent to construct a three-dimensional network to improve swelling resistance and mechanical properties.

[0040] Functional grafting: Following the preparation process of chloromethylated polyethersulfone in Example 1, 5g of the chloromethylated polyethersulfone was dissolved in 100mL of N,N-dimethylformamide. The molar ratio of triethylamine to benzimidazole was adjusted to 1.2:0.8, and the total molar amount was maintained at 3.6mmol to match the chloromethyl content. At the same time, 0.5g of dibromoethane was added as a crosslinking agent, with a molar ratio of 0.1:1 with the chloromethyl group in the chloromethylated polyethersulfone. The mixture was refluxed at 75°C for 10h under nitrogen protection.

[0041] Post-processing: Using the same precipitation and washing steps as in Example 1, the vacuum drying temperature was increased to 65°C to promote the stability of the cross-linked structure, and the drying time was maintained for 6 hours to obtain the cross-linked quaternary ammonium salt-benzimidazole modified polyethersulfone polymer.

[0042] Film formation: A cross-linked quaternary ammonium salt-benzimidazole modified polyethersulfone film, denoted as M2, was prepared according to the general film formation procedure.

[0043] Example 3:

[0044] Based on the bifunctional group ratio of Example 1, this embodiment optimizes the hydrophilicity-hydrophobicity balance through substrate blending, introduces hydroxylated nanoparticles to form additional hydrogen bonds with benzimidazole, and further improves swelling resistance and conductivity.

[0045] Preparation of blended substrate: Take 8g of polyethersulfone and 2g of sulfonated polyethersulfone with a sulfonation degree of 30%, mix and dissolve in 60mL of N,N-dimethylformamide, stir at 50℃ for 4h until completely dissolved to obtain a polyethersulfone / sulfonated polyethersulfone blend; treat the blend using the chloromethylation process of Example 1 to obtain a blended chloromethylated polyethersulfone with a chloromethyl content of 1.7mmol / g.

[0046] Functional grafting: Take 5g of blended chloromethylated polyethersulfone and dissolve it in 100mL of N,N-dimethylformamide. Add 1.7mmol of triethylamine and 1.7mmol of benzimidazole, maintaining the 1:1 bifunctional ratio of Example 1. Then add 0.1g of hydroxylated silica with a particle size of 50nm, accounting for 2% of the polymer mass fraction. After ultrasonic dispersion for 40min, reflux at 70℃ for 9h under nitrogen protection.

[0047] Film formation: A polyethersulfone / sulfonated polyethersulfone-quaternary ammonium salt-benzimidazole-hydroxylated silica composite film was prepared according to the general film formation procedure and denoted as M3.

[0048] Example 4:

[0049] This embodiment, based on Embodiment 3, introduces fluorinated side chains to enhance alkali resistance and composites hydroxylated graphene oxide to strengthen high-temperature dimensional stability, making it suitable for alkaline water electrolysis scenarios at 90℃.

[0050] Preparation of fluorinated functional monomers: Take 0.3g of trifluoroethyl glycidyl ether, a source of fluorinated side chains, and stir with 0.1g of ethylenediamine at 60℃ for 2h to obtain a fluorinated amine monomer, denoted as F-amine.

[0051] Functional grafting: Take 5g of the blended chloromethylated polyethersulfone prepared in Example 3, dissolve it in 100mL of N,N-dimethylformamide, add 1.7mmol of triethylamine and 1.7mmol of benzimidazole to maintain a 1:1 bifunctional ratio, then add 0.05g of F-amine (1% of polymer mass) and 0.05g of hydroxylated graphene oxide (100nm particle size, 1% of polymer mass). After ultrasonic dispersion for 60min, reflux at 75℃ for 12h under nitrogen protection.

[0052] Post-treatment: After cooling, the reaction solution was poured into 50 mL of an ethanol-water mixture (volume ratio 3:1) to precipitate. After filtration, the mixture was washed 5 times with 20 mL of the mixture each time, and then dried under vacuum at 70 °C for 8 h to obtain a fluorine-bifunctional graphene oxide composite polymer.

[0053] Film formation: The film was prepared according to the general film formation steps and denoted as M4. It is suitable for high-temperature scenarios. The degradation of quaternary ammonium salt is inhibited by fluorine-containing side chains, and the sheet-like structure of graphene oxide prevents the film from swelling at high temperatures.

[0054] The chemical structural formulas of fluorinated amine monomers are shown in Formula 3 below:

[0055] C2F3-CH2-O-CH2-CH(OH)-CH2-NH-CH2-CH2-NH2

[0056] Formula 3

[0057] It is prepared by reacting trifluoroethyl glycidyl ether (C2F3-CH2-O-CH2-CH(O)-CH2) with ethylenediamine (H2N-CH2-CH2-NH2); the epoxy group (-CH(O)-CH2-) of trifluoroethyl glycidyl ether undergoes a ring-opening reaction with the amino group (-NH2) of ethylenediamine to generate a fluorinated amine monomer containing hydroxyl (-OH), amino (-NH2, -NH-) and trifluoroethyl (-CH2-C2F3); this monomer is used to introduce fluorinated side chains to improve the alkali resistance of the membrane. The M4 membrane in Example 4 achieves optimized high-temperature alkali resistance through this monomer.

[0058] Example 5:

[0059] Based on Example 2, this embodiment uses gamma-ray radiation crosslinking to replace the chemical crosslinking process, simplifies the process, and introduces nanocellulose to improve water retention capacity, making it suitable for alkaline fuel cell scenarios with low humidity (30% relative humidity).

[0060] Pre-film preparation: Following the functionalized grafting process of Example 2 without the addition of dibromoethane, a non-crosslinked bifunctional polymer was obtained, and a pre-film with a thickness of 0.18 mm was prepared according to the general film formation steps.

[0061] Radiation crosslinking and nanocomposite: The pre-formed film was immersed in an aqueous solution of 0.05 g / mL cellulose nanoparticles with a length of 200 nm, and after immersion at room temperature for 4 hours, it was removed and... 60 A radiation dose of 20 kGy of Co-γ rays was applied, followed by vacuum drying at 60°C for 6 h to obtain a radiation-crosslinked nanocellulose composite membrane, denoted as M5. Radiation crosslinking avoids chemical crosslinking agent residue, and the hydroxyl groups of nanocellulose enhance water retention capacity under low humidity and maintain ion conduction efficiency.

[0062] Comparative Example

[0063] To verify the necessity of the dual-functional synergy, cross-linking enhancement, substrate-nano synergy, and newly added functional components of the present invention, the following comparative examples were set up. Each comparative example is missing only the key optimized components of the corresponding embodiment, and the rest of the processes are the same as those of the corresponding embodiment:

[0064] Comparative Example 1: Monoquaternary Ammonium Salt Group Membrane Deprived of Benzimidazole Synergistic: 5g of chloromethylated polyethersulfone from Example 1 was dissolved in 100mL of N,N-dimethylformamide, with only 3.6mmol of triethylamine added and no benzimidazole added. The mixture was refluxed at 70℃ for 8h. Subsequent precipitation, washing, and film formation steps were the same as in Example 1, resulting in a monoquaternary ammonium salt modified polyethersulfone membrane, denoted as C1.

[0065] Comparative Example 2: Bifunctional non-crosslinked membrane lacking dibromoethane crosslinking agent: 5g of chloromethylated polyethersulfone from Example 1 was dissolved in 100mL of N,N-dimethylformamide, and 1.2mmol of triethylamine and 0.8mmol of benzimidazole were added. The ratio was the same as in Example 2, without crosslinking agent. The mixture was refluxed at 75°C for 10h. Subsequent steps were the same as in Example 2 to obtain a non-crosslinked bifunctional modified polyethersulfone membrane, denoted as C2.

[0066] Comparative Example 3: Pure polyethersulfone substrate without nano-synergistic membrane, sulfonated polyethersulfone blend and hydroxylated silica: Take 5g of pure chloromethylated polyethersulfone from Example 1, without sulfonated polyethersulfone blend, dissolve in 100mL N,N-dimethylformamide, add 1.8mmol triethylamine and 1.8mmol benzimidazole, in the same proportion as in Example 1, without hydroxylated silica, reflux at 70℃ for 9h, and follow the same steps as in Example 3 to obtain a bifunctional modified membrane with pure polyethersulfone substrate, denoted as C3.

[0067] Comparative Example 4: Fluorine-free graphene oxide-free membrane lacking F-amine and GO-OH: Take 5g of the blended chloromethylated polyethersulfone from Example 3, dissolve it in 100mL of N,N-dimethylformamide, add only 1.7mmol of triethylamine and 1.7mmol of benzimidazole, reflux at 75℃ for 12h, and follow the same steps as in Example 4 to obtain a fluorine-free graphene oxide-free composite membrane, denoted as C4 vs. M4, to verify the high-temperature compatibility between the fluorine-containing side chain and graphene oxide.

[0068] Comparative Example 5: Chemically Crosslinked Cellulose-Free Membrane Lacks Radiation Crosslinking and Cellulose: A crosslinked bifunctional membrane was prepared according to the process in Example 2, without radiation treatment and without immersion in cellulose nanoparticles, resulting in a chemically crosslinked membrane without cellulose nanoparticles, denoted as C5 compared to M5, to verify the low-humidity compatibility of radiation crosslinking and cellulose nanoparticles.

[0069] In this invention, Example 2 involves using dibromoethane as a crosslinking agent to form a crosslinked network between the molecular chains of a chloromethyl-containing polyethersulfone-based polymer, thereby improving the anti-swelling performance of the anion exchange membrane. To visually demonstrate that the crosslinking agent can effectively initiate the crosslinking of polymer molecular chains and construct a three-dimensional network structure, such as... Figure 1 As shown, the torque of pure PBAT (poly(dibutyl terephthalate)) increases briefly, then decreases rapidly and stabilizes, indicating that its molecular chains are not significantly cross-linked, and the molecular chains in the melt move relatively freely, lacking a constrained three-dimensional network structure. In contrast, the torque of the PBAT / ADR-1.8 system with added cross-linking agent ADR-1.8 increases continuously over time. This is because the epoxy groups of cross-linking agent ADR-1.8 interact with the active groups of PBAT molecular chains, resulting in a significant increase in melt viscosity.

[0070] In this invention, dibromoethane is used as a crosslinking agent. Its bromoethyl group can undergo a nucleophilic substitution reaction with the chloromethyl group of the polyethersulfone side chain, introducing COC ether bonds between the molecular chains, thereby constructing a three-dimensional crosslinked network. Although the polymer matrix of this invention... Figure 1 Although the types of PBAT (aliphatic polyester) in the product are different, the core mechanism by which the crosslinking agent initiates crosslinking of polymer molecular chains through covalent bonds to form a three-dimensional network to constrain the movement of molecular chains is universal. Figure 1 The continuous increase in torque in the PBAT / ADR-1.8 system directly corroborates the process logic that the crosslinking agent can effectively induce the polymer to form a crosslinked network. Furthermore, in Example 2 of this invention, the swelling degree of the crosslinked membrane material (M2) is significantly lower than that of the uncrosslinked control sample C2. This is precisely due to the constraint effect of the crosslinked network on the movement of the molecular chains. Figure 1 The pattern observed is consistent with the law of cross-linking leading to increased viscosity / network strength and enhanced structural stability.

[0071] pass Figure 1The citations can help illustrate the scientific validity and feasibility of the present invention, which uses a crosslinking agent to construct a three-dimensional network to improve anti-swelling properties.

[0072] Performance testing and results analysis

[0073] (1) Test method

[0074] Swelling resistance test: The membrane was cut into 2cm × 3cm samples and immersed in deionized water at 60℃ for 24h. The water absorption rate and swelling degree were measured. The water absorption rate was calculated as (mass after immersion - dry film mass) / dry film mass × 100%; the swelling degree was calculated as (length after immersion - dry film length) / dry film length × 100%; a new high-temperature swelling test was added: the membrane was immersed in deionized water at 90℃ for 24h, and the high-temperature swelling degree was measured.

[0075] Ion conductivity testing: AC impedance method was used, frequency range 10 Hz. -1 -10 5 Hz, test temperature 30-80℃, the formula for calculating ionic conductivity is σ=L / (R×A), where L is the film thickness, R is the impedance value, and A is the effective area of ​​the film; a new low humidity conductivity test is added: under the conditions of relative humidity 30% and 60℃, the ionic conductivity is measured.

[0076] Alkali resistance test: The membrane was immersed in 1 mol / L potassium hydroxide solution at 80℃ for 1000 h and the ion conductivity retention rate was measured. The calculation method was immersion conductivity after immersion / initial conductivity × 100%, and the change in swelling degree was added. A new high temperature alkali resistance test was added: the membrane was immersed in 1 mol / L potassium hydroxide solution at 90℃ for 500 h and the conductivity retention rate was measured.

[0077] Mechanical performance testing: A universal tensile testing machine was used to measure the tensile strength and elongation at break of the membrane at a stretching rate of 5 mm / min.

[0078] Real-world application simulation test:

[0079] (1) High-temperature water electrolysis scenario: The membrane was assembled into a single cell with Ni-Fe catalyst at the cathode and Ni catalyst at the anode. The test was conducted at 90℃ in a 30% KOH solution, with a flow rate of 1A / cm. 2 Cell voltage and 100-hour stability at current density;

[0080] (2) Low humidity fuel cell scenario: The membrane is assembled into a single cell with Pt / C catalyst at the cathode and Pt-Ru / C catalyst at the anode, with a relative humidity of 30%, 60°C, and 0.5 A / cm². 2 At current density, the discharge power density and stability over 50 hours were tested.

[0081] The test results are shown in Table 1 below:

[0082] Table 1

[0083]

[0084]

[0085] The results are analyzed as follows:

[0086] (1) Microscopic synergistic mechanism verification: The test results of M1-M3 show that the hydrogen bond structure formed by the quaternary ammonium salt and benzimidazole reduces the swelling degree at room temperature by 47.4%-70.5% compared with C1, and the "OH" of benzimidazole - The "relay station" function increases conductivity by 6.9%-19.0%, demonstrating the microscopic synergistic effectiveness of the bifunctional groups.

[0087] (2) High-temperature scene adaptability: Compared with C4, M4 exhibits a 59.5% reduction in swelling at 90℃, and a 39.7% increase in conductivity retention after alkali resistance at 90℃, with a conductivity of 1A / cm. 2 The cell voltage decreased by 0.27V, indicating that the fluorine-containing side chain can inhibit the high-temperature degradation of quaternary ammonium salt, and the sheet-like structure of graphene oxide effectively prevents the membrane from swelling at high temperatures, making it suitable for high-temperature water electrolysis scenarios.

[0088] (3) Adaptability in low humidity scenarios: Compared to C5, M5 exhibits a 66.7% increase in conductivity at 30% RH, with a conductivity of 0.5 A / cm. 2 The power density was increased by 30.3%, proving that while radiation crosslinking simplifies the process, the water retention capacity of nanocellulose can maintain ion conduction efficiency under low humidity, making it suitable for low humidity fuel cell scenarios.

[0089] (4) Multi-dimensional optimization and progression: From M1 basic dual function → M2 cross-linking enhancement → M3 substrate-nano synergy → M4 / M5 scenario adaptation, the overall performance of the membrane is gradually improved, and each embodiment is based on the extension of the previous process, reflecting the continuity of the technical solution.

[0090] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only to the claims and their full scope and equivalents.

Claims

1. A method for preparing a basic anion exchange membrane containing bifunctional groups to synergistically enhance its anti-swelling properties, characterized in that, The method comprises the following steps: (1) functional grafting: chloromethylated polyether sulfone 5 g is dissolved in 100 mL of N,N-dimethylformamide, triethylamine 1.8 mmol and benzimidazole 1.8 mmol are added, and the mixture is refluxed at 70°C under nitrogen protection for 8 h, and stirred every 2 h during the refluxing; (2) post-treatment: after the reaction solution of step (1) is cooled to room temperature, it is poured into 50 mL of ethanol for precipitation, and then filtered and washed with 20 mL of ethanol four times, and then dried at 60°C under vacuum for 6 h to obtain a quaternary ammonium salt-benzimidazole modified polyether sulfone polymer; (3) film forming: the quaternary ammonium salt-benzimidazole modified polyether sulfone film is prepared according to the general film forming procedure.

2. The production method according to claim 1, characterized by, In step (1), the molar ratio of triethylamine to benzimidazole is 1.2:0.8, the total molar amount is 3.6 mmol, and dibromoethane 0.5 g is added at the same time, the molar ratio of dibromoethane to chloromethyl in chloromethylated polyether sulfone is 0.1:1, the refluxing temperature is 75°C, and the refluxing time is 10 h; in step (2), the vacuum drying temperature is 65°C.

3. The production method according to claim 1 or 2, characterized by, It also comprises a blending base material preparation step: polyether sulfone 8 g and sulfonated polyether sulfone 2 g are mixed, dissolved in 60 mL of N,N-dimethylformamide, and stirred at 50°C for 4 h until completely dissolved to obtain a polyether sulfone / sulfonated polyether sulfone blend solution, and the blend solution is subjected to chloromethylation treatment to obtain a blended chloromethylated polyether sulfone; in step (1), the chloromethylated polyether sulfone is replaced by the blended chloromethylated polyether sulfone, and hydroxylated silicon dioxide 0.1 g is added during the functional grafting, and the mixture is ultrasonically dispersed for 40 min before refluxing, and the refluxing time is 9 h.

4. The production method according to claim 3, characterized by, The sulfonation degree of the sulfonated polyether sulfone is 30%, and the chloromethyl content of the blended chloromethylated polyether sulfone is 1.7 mmol / g; the particle size of the hydroxylated silicon dioxide is 50 nm, and the hydroxylated silicon dioxide accounts for 2% of the mass of the blended chloromethylated polyether sulfone.

5. The production method according to claim 3 or 4, characterized by, It also comprises a fluorine-containing functional monomer preparation step: trihydroxyethyl glycidyl ether 0.3 g and ethylenediamine 0.1 g are stirred at 60°C for 2 h to obtain a fluorine-containing amine monomer; in step (1), 0.05 g of the fluorine-containing amine monomer and 0.05 g of hydroxylated graphene oxide are further added during the functional grafting, and the mixture is ultrasonically dispersed for 60 min before refluxing, the refluxing temperature is 75°C, and the refluxing time is 12 h; in step (2), the precipitating solvent is an ethanol-water mixture, and the drying temperature is 70°C, and the drying time is 8 h.

6. The production method according to claim 5, characterized by, The volume ratio of the ethanol-water mixture is 3:1; the particle size of the hydroxylated graphene oxide is 100 nm, and the fluorine-containing amine monomer and the hydroxylated graphene oxide each account for 1% of the mass of the blended chloromethylated polyether sulfone.

7. The preparation method according to claim 1, characterized in that, In step (1) no dibromoethane was added and after obtaining the non-crosslinked bifunctional polymer, a pre-film was prepared according to the general film forming procedure with a thickness of 0.18 mm; further comprising a radiation cross-linking and nanocomposite step: the pre-film was immersed in a nanocellulose aqueous solution, removed after 4 h of room temperature immersion and dried at 60 °C under vacuum for 6 h. 60 Co γ-ray radiation at a dose of 20 kGy, followed by vacuum drying at 60 °C for 6 h.

8. The preparation method according to claim 7, characterized in that, The concentration of the nanocellulose aqueous solution is 0.05 g / mL, and the length of the nanocellulose is 200 nm.

9. A basic anion exchange membrane containing a bifunctional group synergistically improving the anti-swelling property, characterized by, The anion exchange membrane is prepared by the preparation method of any one of claims 1-8, and comprises quaternary ammonium salt groups, benzimidazole groups, and a polyether sulfone base material.

10. The basic anion exchange membrane according to claim 9, characterized by The anion exchange membrane is used in a 90°C alkaline electrolytic water scene or a 30% relative humidity alkaline fuel cell scene.

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