Preparation method of cation exchange membrane for cross-chain transportation

Abstract

The invention relates to a preparation method of a cation exchange membrane for cross-chain transportation. The cation exchange membrane has the advantages of small resistance, high ion transmission rate and good desalting performance. Specifically, the characteristics of a crown ether compound are utilized, a direct and efficient ion transmission channel is provided, the chemical stability of the membrane is improved, specific types of cations can be efficiently screened and transmitted, and the characteristics of the ion channel, such as the size and shape of the channel or the electrophilicity of a functional group, can be further adjusted by chemically modifying the crown ether structure, so that the specific types of cations can be efficiently screened and transmitted. And wider application requirements can be met. Due to the flexible design strategy, the cation exchange membrane is not only suitable for traditional water treatment and chemical raw material purification, but also can be expanded to the high and new technical fields of advanced battery technology, biological medicine separation and the like.

Description

Technical Field

[0001] The invention relates to the field of membrane materials, in particular to a method for preparing a cross-chain transport cation exchange membrane. Background Art

[0002] Cation exchange membranes play a vital role in water treatment, chemical production, and battery manufacturing. Traditional cation exchange membranes mainly transport cations by forming ion channels through ion clusters on polymer side chains. However, this structure usually leads to tortuous ion channels that are difficult to precisely control, thereby reducing the efficiency of ion transmission. This design is particularly prominent in applications that require efficient ion migration.

[0003] In order to solve this technical challenge, the present invention proposes a method for preparing a cation exchange membrane for cross-chain transport, which is based on supramolecular structure optimization, especially the introduction of crown ether compounds to achieve high efficiency of cross-chain transport. Crown ethers are known cyclic supramolecular compounds that are widely studied for ion transport because they can form internal cavities with specific sizes and electrophilicity. In the present invention, the crown ether unit is directly integrated into the polymer backbone, which not only significantly improves the hydrophilicity of the backbone, but also forms a direct and efficient ion transport channel by directly connecting the functional groups on the side chains.

[0004] The core advantage of this design is that the supramolecular responsive channels formed by the crown ether units enable a more linear ion transport path. Compared with traditional membranes, this structure not only reduces the tortuosity of the ion transport path, but also significantly improves the cross-chain transport capacity of ions by optimizing the size and shape of the ion channels. In addition, the specific selectivity of the crown ether also allows the membrane to efficiently screen and transport specific types of cations, such as sodium or potassium ions, which has significant advantages in many industrial applications. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a cation exchange membrane with low resistance, high ion transmission rate and good desalination performance.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: A method for preparing a cation exchange membrane for cross-chain transport, the preparation method comprising the following steps: (1) First, take 3-5 g of biphenyl, 0.5-1 g of dibenzo-18-crown-6, and 4-5 mL of N-methylpiperidone and dissolve them in 5-20 mL of dichloromethane; (2) In an ice bath, add 1-3 mL of trifluoroacetic acid (TFA) at a constant rate, then add 10-33 mL of TFSA (trifluoromethanesulfonic acid), and continue the reaction for 3-5 hours. (3) pouring the viscous mixture obtained in step (2) into deionized water for elution to obtain a polymer solid; (4) Elute the polymer solid again with 1-3 mol / L sodium bicarbonate solution until it turns red; then place in a vacuum drying oven and dry at 60-80 °C for 10-24 h; (5) Take 1-3 g of the above-mentioned dry polymer and dissolve it in 20-50 mL of dimethyl sulfoxide (DMSO), add 1-3 mL of propane sultone, react at 60-80 °C for 5-8 h, and elute with acetone to obtain a functionalized polymer; (6) Take 0.5-1 g of the functionalized polymer and dissolve it in 10-15 mL of dimethyl sulfoxide (DMSO) to obtain a red transparent solution; (7) Pour the above red transparent solution onto a glass plate, place it in a vacuum drying oven, and dry it at 60-80 °C for 10-24 h to obtain a cation exchange membrane with cross-chain transport function.

[0007] Furthermore, the dimethyl sulfoxide (DMSO) film casting solvent can be replaced by DMAC or DMF. Furthermore, the cation exchange membrane has a thickness of 80-110 μm.

[0008] Furthermore, in the step (3), deionized water is poured in for elution 3 to 5 times to ensure that the residual solvent is completely washed away.

[0009] Compared with the prior art, the present invention has the following beneficial effects: The present invention relates to a method for preparing a cross-chain transport cation exchange membrane. This method has many significant advantages over existing materials and technologies, which are mainly reflected in the following aspects: (1) More direct ion transport path: By utilizing the characteristics of crown ether compounds, the present invention provides a direct and efficient ion transport channel. The cyclic supramolecular structure of crown ether forms an internal cavity with a specific size and electrophilicity, which not only reduces the tortuosity of the ion transport path, but also significantly improves the cross-chain transport capacity of ions by optimizing the size and shape of the ion channel.

[0010] (2) Enhanced chemical stability and optimized resistance characteristics: The introduction of crown ethers improves the physical and chemical properties of cation exchange membranes. This includes improved chemical stability of the membrane, enabling it to work stably in a wider range of chemical environments, as well as optimized electrical resistance characteristics to reduce energy loss, which is particularly important for battery manufacturing and other energy-intensive applications.

[0011] (3) Efficient screening and transport of specific cations: The specific selectivity of crown ethers allows the new membrane to efficiently screen and transport specific types of cations, such as sodium or potassium ions. This property has significant application advantages in fields such as water treatment, chemical production and advanced battery technology.

[0012] (4) Operational flexibility and wide application potential: By chemically modifying the crown ether structure, the characteristics of the ion channel, such as the size and shape of the channel or the electrophilicity of the functional group, can be further adjusted to meet a wider range of application requirements. This flexible design strategy makes the cation exchange membrane not only suitable for traditional water treatment and chemical raw material purification, but also can be extended to high-tech fields such as advanced battery technology and biomedical separation. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is further described below through specific embodiments, but the protection scope of the present invention is not limited thereto: Example 1 (1) First, take 4.2 g of biphenyl, 0.9 g of diphenyl 18-crown 6, and 4.1 mL of N-methylpiperidone and dissolve them in 10 mL of dichloromethane.

[0014] (2) In an ice bath, add 3 mL of trifluoroacetic acid (TFA) at a constant rate. Then add 25 mL of trifluoromethanesulfonic acid (TFSA). The reaction lasts for 5 hours.

[0015] (3) The viscous mixture was poured into deionized water for elution to obtain a polymer solid.

[0016] (4) In order to clean the acid inside, it was eluted again in a 2 mol / L sodium bicarbonate solution until the polymer turned red. It was then placed in a vacuum drying oven and dried at 80 °C for 24 h.

[0017] (5) Dissolve 1 g of the above dried polymer in 20 mL of dimethyl sulfoxide (DMSO) and add 1 mL of propane sultone. React at 60 °C for 8 h. Elute with acetone to obtain the functionalized polymer.

[0018] (6) Dissolve 1 g of the above polymer in 15 mL of dimethyl sulfoxide (DMSO) to obtain a red transparent solution.

[0019] (7) Pour the above red transparent solution onto a glass plate and place it in a vacuum drying oven and dry it at 80 °C for 24 h. Finally, the cation exchange membrane AEM-1 with cross-chain transport function is obtained.

[0020] Example 2 (1) First, take 4.05 g of biphenyl, 1.0 g of diphenyl 18-crown 6, and 4.1 mL of N-methylpiperidone and dissolve them in 10 mL of dichloromethane.

[0021] (2) In an ice bath, add 3 mL of trifluoroacetic acid (TFA) at a constant rate. Then add 25 mL of trifluoromethanesulfonic acid (TFSA). The reaction lasts for 5 hours.

[0022] (3) The viscous mixture was poured into deionized water for elution to obtain a polymer solid.

[0023] (4) In order to clean the acid inside, it was eluted again in a 2 mol / L sodium bicarbonate solution until the polymer turned red. It was then placed in a vacuum drying oven and dried at 80 °C for 24 h.

[0024] (5) Dissolve 1 g of the above dried polymer in 20 mL of dimethyl sulfoxide (DMSO) and add 1 mL of propane sultone. React at 60 °C for 8 h. Elute with acetone to obtain the functionalized polymer.

[0025] (6) Dissolve 1 g of the above polymer in 15 mL of dimethyl sulfoxide (DMSO) to obtain a red transparent solution.

[0026] (7) Pour the above red transparent solution onto a glass plate and place it in a vacuum drying oven and dry it at 80 °C for 24 h. Finally, the cation exchange membrane AEM-2 with cross-chain transport function is obtained.

[0027] Example 3 (1) First, take 3.5 g of biphenyl, 1.8 g of diphenyl 18-crown 6, and 4.1 mL of N-methylpiperidone and dissolve them in 10 mL of dichloromethane.

[0028] (2) In an ice bath, add 3 mL of trifluoroacetic acid (TFA) at a constant rate. Then add 25 mL of trifluoromethanesulfonic acid (TFSA). The reaction lasts for 5 hours.

[0029] (3) The viscous mixture was poured into deionized water for elution to obtain a polymer solid.

[0030] (4) In order to clean the acid inside, it was eluted again in a 2 mol / L sodium bicarbonate solution until the polymer turned red. It was then placed in a vacuum drying oven and dried at 80 °C for 24 h.

[0031] (5) Dissolve 1 g of the above dried polymer in 20 mL of dimethyl sulfoxide (DMSO) and add 1 mL of propane sultone. React at 60 °C for 8 h. Elute with acetone to obtain the functionalized polymer.

[0032] (6) Dissolve 1 g of the above polymer in 15 mL of dimethyl sulfoxide (DMSO) to obtain a red transparent solution.

[0033] (7) Pour the above red transparent solution onto a glass plate and place it in a vacuum drying oven and dry it at 80 °C for 24 h. Finally, the cation exchange membrane AEM-3 with cross-chain transport function is obtained.

[0034] The performance of the prepared cation exchange membrane with cross-chain transport function is tested below: Test 1: The prepared membrane was tested for resistance and compared with commercial membranes Fuji No. Ⅰ cationic membrane and Nafion 115. See Table 1 for specific results.

[0035] Table 1: Surface resistance of the prepared membrane and two commercial membranes Test 2: The chemical stability of the prepared cation exchange membrane in sodium hydroxide solution was tested to investigate the chemical stability of the cation exchange membrane. The weight loss rate was used as an indicator and the weight difference was used as an indicator to evaluate its chemical stability. After being completely dried in a vacuum oven at 80°C for 24 hours, the weight of the sample was recorded. Then, the dried ion exchange membrane sample was soaked in a 2.0M sodium hydroxide solution at 80°C for 24 hours, 48 ​​hours, and 96 hours, and then the retained solution on the surface of the sample was carefully wiped, and the soaked membrane was washed with water until the water became neutral. Then, the ion exchange membrane sample was dried at 80°C under vacuum conditions for 24 hours, and then the membrane mass was re-weighed. The mass loss was used to characterize the alkali resistance stability. See Table 2 for specific results.

[0036] Table 2: Weight loss rate of membranes immersed in 2.0 mol / L sodium hydroxide solution at different time periods Test 3: Compare the water absorption of the prepared cation exchange membrane with Fuji No. Ⅰ cation membrane and Nafion115 at different temperatures. After the tested membrane sample is completely dried in a vacuum drying oven at 80℃ for 24h, the length of the membrane sample is recorded. Then, the dried ion exchange membrane sample is soaked in deionized water at 20℃, 30℃, and 40℃ for 48h. Then, the retained solution on the surface of the sample is carefully wiped and the weight of the membrane sample is recorded. Calculate the weight change of the sample compared to the dry state. See Table 3 for specific results.

[0037] Table 3: Water absorption of test samples at different temperatures Embodiments 1 to 3 are only preferred embodiments of the present invention, and are not intended to limit the present invention in any other form. Any person skilled in the art may use the above technical content as inspiration to change or modify the equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments without departing from the technical essence of the claims of the present invention shall still fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a cation exchange membrane for cross-chain transport, characterized in that: The preparation method comprises the following steps: (1) First, take 3-5 g of biphenyl, 0.5-1 g of dibenzo-18-crown-6, and 4-5 mL of N-methylpiperidone and dissolve them in 5-20 mL of dichloromethane; (2) In an ice bath, add 1-3 mL trifluoroacetic acid (TFA) at a constant rate, then add 10-33 mL TFSA (trifluoromethanesulfonic acid), and continue the reaction for 3-5 hours. (3) pouring the viscous mixture obtained in step (2) into deionized water for elution to obtain a polymer solid; (4) Elute the polymer solid again with 1-3 mol / L sodium bicarbonate solution until it turns red; then place in a vacuum drying oven and dry at 60-80 °C for 10-24 h; (5) Take 1-3 g of the above-mentioned dry polymer and dissolve it in 20-50 mL of dimethyl sulfoxide (DMSO), add 1-3 mL of propane sultone, react at 60-80 °C for 5-8 h, and elute with acetone to obtain a functionalized polymer; (6) Take 0.5-1 g of the functionalized polymer and dissolve it in 10-15 mL of dimethyl sulfoxide (DMSO) to obtain a red transparent solution; (7) Pour the above red transparent solution onto a glass plate, place it in a vacuum drying oven, and dry it at 60-80 °C for 10-24 h to obtain a cation exchange membrane with cross-chain transport function.

2. The method for preparing a cation exchange membrane for cross-chain transport according to claim 1, characterized in that: The dimethyl sulfoxide (DMSO) film casting solvent can be replaced by DMAC or DMF.

3. The method for preparing a cation exchange membrane for cross-chain transport according to claim 1, characterized in that: The thickness of the cation exchange membrane is 80-110 μm.

4. The method for preparing a cation exchange membrane for cross-chain transport according to claim 1, characterized in that: In the step (3), deionized water is poured in for 3 to 5 times to ensure that the residual solvent is completely washed away.

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