Crosslinked composite membrane and preparation method thereof

Abstract

The invention belongs to the technical field of ion exchange membranes, and provides a cross-linked composite membrane and a preparation method thereof.The preparation method comprises the steps that soluble target polymer resin is dissolved in a solvent, halogenated alkyne and pyridine-containing organic matter are added into the solution, the mixture is stirred to react at a certain temperature, and the cross-linked composite membrane is obtained; halogenated alkyne and pyridine-containing organic matter are polymerized and cross-linked to generate a cationic polymer, reaction liquid is cast into a membrane preparation mold, a solvent is removed through heat treatment to form a membrane material, impurities are removed through ion exchange, and the cross-linked composite membrane is obtained. The preparation method has the advantages of mild synthesis conditions, simple process, large-scale preparation, high ionic conductivity, high mechanical strength, low swelling property and low gas permeation, can be applied to an application system needing rapid ion conduction, and has wide application prospects. The lithium ion battery can be used in the fields of hydrogen-oxygen fuel cells, direct alcohol fuel cells, electrolyzed water, flow batteries, chlor-alkali industry, water treatment, lithium metal batteries, lithium ion batteries and the like.

Description

Technical Field

[0001] This invention relates generally to the field of ion exchange membrane technology, and specifically to a cross-linked composite membrane and its preparation method. Background Technology

[0002] Ion exchange membranes, including anion exchange membranes and cation exchange membranes, are key materials for devices used in water electrolysis for green hydrogen production, fuel cell applications, water treatment, flow batteries, chlor-alkali industry, and high-value carbon dioxide reduction.

[0003] Ultrathin ion exchange membranes are currently a key development direction in the industry. Developing ultrathin, highly stable, high-ion-conductivity, and low-permeability ion exchange membranes can improve the power performance, energy efficiency, and lifespan of devices, while reducing equipment costs. However, the use of ultrathin ion exchange membranes still faces challenges such as poor membrane stability, severe swelling, significant permeation of active substances, and insufficient ion conduction. New concepts are needed to address these issues.

[0004] Cross-linking is a commonly used method to improve membrane stability and reduce swelling. However, current cross-linked membrane preparation methods still face challenges such as poor controllability, complex preparation processes, insufficient membrane lifespan, and severe permeation of active materials. For example, in fuel cells and water electrolysis systems, ultrathin ion exchange membranes struggle to address hydrogen cross-permeation, severely impacting device safety. Similarly, in flow battery systems, cross-permeation of active ions affects energy efficiency and device lifespan.

[0005] By employing a cross-linked cationic polymer (CCP) synthesis method, the excellent mechanical properties and ion-selective transport capabilities of CCPs are utilized. During the synthesis process, the CCPs exhibit excellent physical entanglement with soluble polymers, avoiding the sedimentation-induced uniformity issues associated with CCP synthesis and achieving efficient physical cross-linking of soluble polymers. The resulting CCP-reinforced ion exchange membrane possesses superior mechanical properties and active material permeation inhibition, allowing for the development of ion exchange membrane materials with better mechanical properties, lower swelling, stronger ion conductivity, lower active material permeation, and thinner thickness. Summary of the Invention

[0006] To address the shortcomings or improvement needs of existing technologies, this invention aims to provide a cross-linked composite membrane and its preparation method. The composite membrane comprises a cross-linked cationic polymer and a non-cross-linked polymer resin. The cross-linked cationic polymer is formed by the spontaneous reaction of a haloalkyne with a pyridine-containing organic compound. The non-cross-linked polymer resin permeates the cross-linked cationic polymer, forming a three-dimensional cross-linked network. The cross-linked solution is then cast and dried to form the composite membrane. This method is simple to operate, allows for easy control of the membrane's cross-linking degree, and is applicable to various membrane materials. This method can reduce the thickness of ion exchange membranes, decrease membrane swelling ratio, improve membrane mechanical stability, and suppress cross-permeation of active substances, resulting in a low-cost, high-power, high-efficiency, and highly stable ion exchange membrane material.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A crosslinked composite membrane is provided, comprising a crosslinked cationic polymer and a non-crosslinked polymer resin; the crosslinked cationic polymer is formed by the spontaneous reaction of a haloalkyne with a pyridine-containing organic compound, and the non-crosslinked polymer resin is formed from a soluble target polymer; the non-crosslinked polymer resin penetrates the crosslinked cationic polymer, forming a three-dimensional crosslinked network, and the crosslinked composite membrane is formed by casting and heat treatment; the infrared spectrum of the crosslinked composite membrane is within 1640±20 nm. -C=CN appears + Signal peak.

[0008] Another aspect of the present invention provides a method for preparing the above-mentioned crosslinked composite film, comprising the following steps: Step 1: Dissolve the soluble target polymer in a solvent and stir until completely dissolved to form a homogeneous target polymer solution; Step 2: Dissolve the haloalkyne and pyridine-containing organic compound in the homogeneous target polymer solution, stir and react for a period of time at a certain temperature, and form a cross-linked structure in situ in the target polymer solution system through the quaternization reaction and spontaneous cross-linking polymerization between the haloalkyne and the pyridine-containing organic compound, to obtain the cross-linked ionic polymer casting solution. Step 3: Cast the above casting solution into the film forming mold, heat treat it at a certain temperature for a period of time to remove the residual solvent, and obtain the cross-linked composite film.

[0009] Furthermore, the soluble target polymer in step one is one or a mixture of neutral polymers, cation exchange polymers, and anion exchange polymers, and the soluble target polymer is selected from one or a mixture of the following structural formulas: , , , , , , , , , , , , Where m and n are positive integers, and the range of values ​​is n > 10 and m ≥ 0.

[0010] Furthermore, the solvent in step one above is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol, ethanol, acetonitrile, isopropanol, toluene, dichloromethane, and water.

[0011] Furthermore, the halogenated alkyne in step two above is one or more combinations of 3-chloropropyne, 3-bromopropyne, 1-bromo-2-butyne and 3-iodopropyne, and the pyridine-containing organic compound is selected from one or more of the following structures; , , , , , , , , , , , , , , Where n and m are positive integers, and the range of values ​​is n > 10 and m ≥ 0.

[0012] Furthermore, in step two above, the amounts of added haloacetylene and pyridine-containing organic compounds are expressed as a molar ratio, with the ratio of haloacetylene to pyridine groups in the pyridine-containing organic compounds being between 0.3 and 1.2; the sum of the masses of added haloacetylene and pyridine-containing organic compounds is 5%-500% of the mass of the soluble polymer; the reaction temperature in step two is between 20 and 120°C, and the reaction time is 5 min-24 h.

[0013] Furthermore, the heat treatment temperature in step three is 50-150 ℃, and the treatment time is 5 min-24 h.

[0014] Furthermore, when the soluble polymer is an anion exchange resin or a cation exchange resin, the process further includes a fourth step of removing impurities through ion exchange. When the target soluble polymer is an anion exchange resin, it is exchanged with an alkaline aqueous solution, and when it is a cation exchange resin, it is exchanged with an acidic aqueous solution. The exchange time is 1 h to 24 h to remove impurities and transform it into a membrane capable of conducting specific ions.

[0015] Compared with the prior art, the advantage of this invention lies in: I. This invention utilizes a cross-linked cationic polymer preparation and synthesis method. It takes advantage of the excellent mechanical properties and ion-selective transport function of the cross-linked cationic polymer formed by haloalkynes and pyridine-containing organic compounds. During the synthesis of the cross-linked cationic polymer, it can form a good physical entanglement with the soluble target polymer, avoiding the problem of poor uniformity caused by sedimentation during the synthesis of the cross-linked cationic polymer, and also achieving efficient physical cross-linking of the cross-linked cationic polymer with the soluble polymer.

[0016] Second, this invention achieves precise control over the degree of membrane crosslinking and functionalized cations through the quantitative reaction of haloalkynes and pyridine groups. It can customize the swelling degree and mechanical strength of composite polymers for different application scenarios, and construct a stable network that combines mechanical framework and ion transport function, significantly improving the consistency and stability of composite polymer performance.

[0017] Third, the cross-linked cationic polymer-reinforced ion exchange membrane obtained by the present invention is produced by in-situ quaternization and spontaneous polymerization of halogenated alkynes and pyridine-containing organic compounds in a soluble polymer solution to obtain a cross-linked ion polymer network. It has better mechanical properties and active material permeation inhibition effect, and can be used to develop ion exchange membrane materials with better mechanical properties, lower swelling, stronger ion conduction, lower active material permeation, and thinner thickness.

[0018] This invention enables large-scale preparation under mild conditions and with a simple process, and can be applied to a variety of scenarios. Attached Figure Description

[0019] These and / or other aspects and advantages of the present invention will become clearer and more readily understood from the following detailed description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the crosslinked sulfonated polyether ether ketone obtained in Example 1 of the present invention; Figure 2 The infrared signal spectrum of the cross-linked sulfonated polyether ether ketone proton exchange membrane obtained in Example 1 of the present invention; Figure 3 The bar chart shows the water absorption rate and swelling degree of the cross-linked Nafion membrane obtained in Example 2 of the present invention and the non-cross-linked Nafion membrane obtained under the same conditions. Figure 4 The bar chart shows the water absorption rate and swelling degree of the cross-linked polyarylene ether sulfone anion exchange membrane obtained in Example 3 of the present invention and the uncross-linked polyarylene ether sulfone anion exchange membrane obtained under the same conditions. Figure 5 The bar chart shows the water absorption rate and swelling degree of the cross-linked reinforced polystyrene anion exchange membrane obtained in Example 4 of the present invention and the non-cross-linked polystyrene anion exchange membrane obtained under the same conditions. Figure 6 The graph shows the conductivity curves of the cross-linked polyethylene glycol film obtained in Example 5 of the present invention and the non-cross-linked polyethylene glycol film obtained under the same conditions at different temperatures. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments.

[0021] Example 1 A cross-linked composite membrane, the preparation method of which includes the following steps: (1) Take 10g of sulfonated polyether ether ketone resin (whose molecular structure is...) (where n is >10) is completely dissolved in 200 ml of N,N-dimethylformamide solvent; (2) Add 1.18 g of bromopropyne and 0.8 g of bipyridine (molecular formula: ...) to the above solution. The reaction was carried out at 60°C for 30 min. (3) The above reaction solution is poured into a film forming mold and dried at 80°C to remove the solvent for 5 hours to obtain the film material. (4) The obtained membrane material is placed in a 0.5 M dilute sulfuric acid solution for ion exchange to obtain a cross-linked composite membrane, namely a cross-linked sulfonated polyether ether ketone proton exchange membrane.

[0022] A schematic diagram of the cross-linked sulfonated polyetheretherketone proton exchange membrane obtained in this embodiment is shown below. Figure 1 As shown, large-area fabrication is possible, and the thickness of the fabricated film is 15 μm, which is lower than the 25 μm thickness of the commonly used Nafion 211 film in this field. Figure 2 As shown, the infrared spectrum of the crosslinked sulfonated polyether ether ketone proton exchange membrane obtained in this embodiment is within 1640±20. -C=CN appears + The signal peaks indicate that the product prepared in this embodiment was successful.

[0023] Example 2 A cross-linked composite membrane, the preparation method of which includes the following steps: (1) Add 8g of Nafion proton exchange resin (molecular structure) (where n is >10) is dissolved in 160 ml of N,N-dimethylformamide solvent; (2) Add 1.4 g of 3-chloropropyne and 2 g of 2,4,6-tris(4-pyridine)1,3,5-triazine (molecular structure: The reaction was carried out at 80°C for 10 min. (3) The above reaction solution was poured into a film forming mold and vacuum dried at 70 °C to remove the solvent for 8 h to obtain the film material. (4) The obtained membrane material is placed in 1 L of dilute sulfuric acid solution (0.5 M) for ion exchange to obtain a cross-linked composite membrane, namely a cross-linked Nafion membrane.

[0024] like Figure 3 As shown, the cross-linked Nafion membrane obtained in this embodiment is compared with the non-cross-linked Nafion membrane obtained under the same conditions (the only difference being the absence of halogenated alkynes and pyridine-containing organic matter in step two) in terms of water absorption rate and swelling degree. Specifically, an electronic balance and vernier calipers were used to measure the membrane's weight and size in dry and wet states. First, the membrane was cut into approximately 1×4 cm strips and placed in a vacuum drying oven to remove moisture. The weight, length, and width of the membrane at this point were measured, denoted as W1 and S1, respectively. Then, the membrane was immersed in deionized water to completely absorb water, and the weight, length, and width of the membrane after water absorption were measured, denoted as W2 and S2, respectively. The water absorption rate of the membrane was obtained from (W2-W1) / W2, and the swelling degree of the membrane was obtained from (S2-S1) / S1. The obtained data were plotted as follows: Figure 3 The bar chart shows that the presence of sulfonic acid groups and the introduction of 2,4,6-tris(4-pyridine)1,3,5-triazine in the membrane increases the water absorption rate. At the same time, the cross-linked three-dimensional network restricts the extension of molecular chains and reduces swelling. It can be seen that the performance of the product in this embodiment is significantly improved.

[0025] Example 3 A cross-linked composite membrane, the preparation method of which includes the following steps: (1) 7g of polyarylethersulfone anion exchange resin (molecular structure) (where n is >10) is completely dissolved in 150 ml of dimethyl sulfoxide solvent; (2) Add 2 g of 1-bromo-2-butyne and 1 g of tetrapyridine porphyrin (molecular structure is) to the above solution. The reaction was carried out at 50°C for 2 hours. (3) The above reaction solution is poured into a film forming mold and dried at 80°C to remove the solvent for 3 hours to obtain the film material. (4) The obtained membrane material is placed in a 1 M sodium hydroxide solution for ion exchange to obtain a cross-linked composite membrane, namely a cross-linked polyarylene sulfone anion exchange membrane.

[0026] like Figure 4 As shown, the cross-linked polyarylene ether sulfone anion exchange membrane obtained in this embodiment was compared with the non-cross-linked polyarylene ether sulfone anion exchange membrane obtained under the same conditions (the only difference being the absence of halogenated alkynes and pyridine-containing organic matter in step two) in terms of water absorption rate and swelling degree. Specifically, an electronic balance and vernier calipers were used to measure the membrane's weight and size in dry and wet states. First, the membrane was cut into approximately 1×4 cm strips and placed in a vacuum drying oven to remove moisture. The weight, length, and width of the membrane at this point were measured. The mass was recorded as W1, and the area as S1. Then, the membrane was immersed in deionized water to completely absorb water. The weight, length, and width of the membrane after water absorption were measured. The mass was recorded as W2, and the area as S2. (W2-W1) / W2 yielded the water absorption rate of the membrane, and (S2-S1) / S1 yielded the swelling degree of the membrane. The obtained data were plotted as follows: Figure 4 The bar chart shows that the presence of sulfonic acid groups and the introduction of tetrapyridine porphyrin to increase hydrophilicity within the membrane increases the water absorption rate of the membrane. At the same time, the cross-linked three-dimensional network restricts molecular chain extension and reduces swelling. It can be seen that the performance of the product in this embodiment is significantly improved.

[0027] Example 4 A cross-linked composite membrane, the preparation method of which includes the following steps: (1) 12 g of polystyrene anion exchange resin (molecular structure) (where n>10, m≥0) is completely dissolved in a mixed solvent of 200 ml N-methylpyrrolidone and 100 ml dimethyl sulfoxide; (2) Add 3.2 g of 3-iodopropyne and 3 g of tripyridylamine (molecular structure: Stir and react for 3 hours; (3) The above reaction solution is poured into a film forming mold and dried at 90°C to remove the solvent for 2 hours to obtain the film material. (5) The obtained membrane material is placed in 1 L of sodium hydroxide solution for ion exchange to obtain a cross-linked composite membrane, namely a cross-linked polystyrene anion exchange membrane.

[0028] like Figure 5As shown, the cross-linked polystyrene anion exchange membrane obtained in this embodiment was compared with the non-cross-linked polystyrene anion exchange membrane obtained under the same conditions (the only difference being the absence of halogenated alkynes and pyridine-containing organic matter in step two) in terms of water absorption rate and swelling degree. Specifically, an electronic balance and vernier calipers were used to measure the membrane's weight and size in dry and wet states. First, the membrane was cut into approximately 1×4 cm strips and placed in a vacuum drying oven to remove moisture. The weight, length, and width of the membrane at this point were measured. The mass was recorded as W1, and the area as S1. Then, the membrane was immersed in deionized water to completely absorb water. The weight, length, and width of the membrane after water absorption were measured. The mass was recorded as W2, and the area as S2. (W2-W1) / W2 yielded the water absorption rate of the membrane, and (S2-S1) / S1 yielded the swelling degree of the membrane. The obtained data were plotted as follows: Figure 5 The bar chart shows that the presence of sulfonic acid groups and the introduction of tripyridylamine to increase hydrophilicity within the membrane increases the water absorption rate of the membrane. At the same time, the cross-linked three-dimensional network restricts molecular chain extension and reduces swelling. It can be seen that the performance of the product in this embodiment is significantly improved.

[0029] Example 5 A cross-linked composite membrane, the preparation method of which includes the following steps: (1) Take 3 g of polyethylene glycol (molecular structure) (where n is >10) is completely dissolved in a mixed solvent of 100 ml N-methylpyrrolidone and 10 ml pyridine; (2) Add 3 g of 3-bromopropyne and 4 g of 2,4,6-tris(4-pyridine)1,3,5-triazine (molecular structure is...) to the above solution. Stir and react at 30 ℃ for 2 h; (3) The above reaction solution is poured into a film forming mold and dried at 85 degrees to remove the solvent for 4 hours to obtain the film material. (5) The obtained membrane material is placed in 1.5L sodium hydroxide solution for ion exchange to obtain a cross-linked composite membrane, namely a cross-linked polyethylene glycol membrane.

[0030] like Figure 6 As shown, the conductivity of the cross-linked polyethylene glycol membrane obtained in this embodiment is compared with that of the uncross-linked polyethylene glycol membrane obtained under the same conditions (the only difference being the absence of halogenated alkynes and pyridine-containing organic compounds in step two). Specifically, the ionic resistance of the membrane was obtained using four-probe ESI technology, and then the in-plane conductivity of the membrane was calculated using the formula: (L is the distance between the two electrodes, 3 cm; R is the membrane resistance; W and d are the sample width and thickness, respectively.) The membrane needs to be stabilized for 10 minutes at different temperatures before the membrane resistance can be measured. The obtained data is then fitted to obtain... Figure 6As can be seen from the curve, the performance of the product in this embodiment has been significantly improved.

[0031] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cross-linked composite membrane, characterized in that, Including cross-linked cationic polymers and non-cross-linked polymer resins; The cross-linked cationic polymer is formed by the spontaneous reaction of haloalkynes and pyridine-containing organic compounds, while the non-cross-linked polymer resin is formed by the soluble target polymer. The non-crosslinked polymer resin permeates the crosslinked cationic polymer, forming a three-dimensional crosslinked network, and the crosslinked composite film is formed by casting and heat treatment; the infrared spectrum of the crosslinked composite film is within 1640±20. A -C=C-N+ signal peak appears.

2. A method for preparing a cross-linked composite membrane as described in claim 1, characterized in that, Includes the following steps: Step 1: Dissolve the soluble target polymer in a solvent and stir until completely dissolved to form a homogeneous target polymer solution; Step 2: Dissolve the haloalkyne and the pyridine-containing organic compound in the homogeneous target polymer solution, stir and react for a period of time at a certain temperature, and form a cross-linked structure in situ in the homogeneous target polymer solution through the quaternization reaction between the haloalkyne and the pyridine-containing organic compound and spontaneous cross-linking polymerization to obtain a cross-linked ionic polymer casting solution. Step 3: Cast the cross-linked ionomer casting solution into a film-forming mold, heat-treat it at a certain temperature for a period of time, remove the solvent, and obtain the cross-linked composite film.

3. The method for preparing the cross-linked composite membrane according to claim 2, characterized in that: The soluble target polymer in step one is one or more of neutral polymers, cation exchange polymers, and anion exchange polymers, and the soluble target polymer is selected from one or more of the following structural formulas: ， ， ， ， ， ， ， ， , , ， Where n and m are positive integers, and the range of values ​​is n > 10 and m ≥ 0.

4. The method for preparing the cross-linked composite membrane according to claim 2, characterized in that: The solvent in step one is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol, ethanol, acetonitrile, isopropanol, toluene, dichloromethane, and water.

5. The method for preparing a cross-linked composite membrane according to claim 2, characterized in that: The haloacetylene in step two is one or a combination of 3-chloropropyne, 3-bromopropyne, 1-bromo-2-butyne and 3-iodopropyne.

6. The method for preparing a cross-linked composite membrane according to claim 2, characterized in that: The pyridine-containing organic compound in step two is selected from one or more of the following structures; ， ， ， , ， , , , ， , , , ， ， Where n and m are positive integers, and the range of values ​​is n > 10 and m ≥ 0.

7. The method for preparing the cross-linked composite membrane according to claim 2, characterized in that: In step two, the molar ratio of the added haloalkynes to the pyridine groups in the pyridine-containing organic compounds is 0.3-1.2, so that they can spontaneously crosslink to form cationic polymers after quaternization.

8. The method for preparing the cross-linked composite membrane according to claim 2, characterized in that: In step two: the sum of the mass of the halogenated alkyne and the pyridine-containing organic compound is 5%-500% of the mass of the soluble polymer; the reaction temperature is between 20-120℃, and the reaction time is 5 min-24 h.

9. The method for preparing the cross-linked composite membrane according to claim 2, characterized in that: The heat treatment temperature in step three is 50-150℃, and the treatment time is 5 min-24 h.

10. The method for preparing the cross-linked composite membrane according to claim 2, characterized in that: When the target soluble polymer is an anion exchange resin or a cation exchange resin, the process further includes step four: ion exchange of the cross-linked composite membrane to remove impurities.

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