Difunctional light-operated pore-forming ion exchange membrane as well as preparation method and application thereof

Abstract

The invention discloses a difunctional light-operated pore-forming ion exchange membrane as well as a preparation method and application thereof, and belongs to the technical field of ion exchange membrane materials. Sulfonated polyphenylacetylene with a sulfonic acid group and a polyphenylacetylene chain segment is used as a raw material and is further grafted to polyvinyl alcohol PVA through a low-temperature esterification reaction, PVA hydroxyl (-OH) and the sulfonic acid group (-SO3-) form a physical cross-linked network through hydrogen bonds and ion-dipole interaction, photosensitive double bonds of the polyphenylacetylene chain segment and a photo-crosslinking agent form a covalent network, and the polyphenylacetylene chain segment and the photo-crosslinking agent form a covalent network. Uniformly embedding the reinforcing filler into the PVA substrate, controlling an ultraviolet irradiation area through a porous mask, performing photo-crosslinking on an exposure area to form a compact network, keeping an unexposed area in a soluble state, and washing with water to form a through pore channel, so as to obtain the polyvinyl alcohol PVA ion exchange membrane with controllable porosity and pore diameter. According to the polyvinyl alcohol PVA ion exchange membrane, the ionic conductivity, the mechanical strength and the chemical stability are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ion exchange membrane materials, and particularly relates to a dual-functional light-controlled pore-forming ion exchange membrane, a preparation method thereof, and an application thereof. Background Art

[0002] As a polymer material with selective ion transport function, the ion exchange membrane has become a core component of modern industrial and energy technologies by virtue of its characteristic of screening counter ions through electrostatic action of fixed ionic groups, and is widely used in electrochemical devices, water treatment, chemical separation and emerging fields. In electrochemical devices, the ion exchange membrane is the proton exchange membrane of fuel cells, the diaphragm of electrolytic cells, and the electrolyte barrier layer of flow batteries, directly affecting the energy conversion efficiency and system life. For example, the Nafion membrane in fuel cells has become the first choice for high power density applications by conducting hydrogen ions and isolating fuels from oxidants, but its high cost and environmental hazards of the perfluorination process limit large-scale applications.

[0003] An ideal ion exchange membrane should have high ion conductivity, low swelling rate, excellent chemical stability and selective permeability. However, current mainstream materials all have significant limitations. Although perfluorosulfonic acid membranes have excellent performance, their cost and environmental problems are difficult to overcome; non-fluorinated polymers such as polyetheretherketone (PEEK) and polybenzimidazole (PBI) rely on strong acid doping, resulting in a decrease in mechanical strength. Polyvinyl alcohol (PVA) is regarded as a potential alternative material due to its good film-forming property, hydrophilicity and biocompatibility, but the proton conductivity of unmodified PVA membranes is only 0.01 - 0.03 S / cm, and the water absorption rate can reach 200% at high humidity, easily leading to structural collapse. More critically, the structure of traditional PVA membranes is dense, relying on ion diffusion rather than continuous transport channels, further limiting its efficiency.

[0004] In recent years, due to the advantages of high efficiency, energy saving, precise controllability and environmental friendliness, the photocuring technology has provided new ideas for the modification of polymer materials and the preparation of membranes. For example, the photocrosslinking technology can significantly reduce the swelling rate of chitosan membranes, and the digital light processing (DLP) technology can prepare porous membranes with a pore size deviation of ±5%. However, combining photocuring with PVA faces two challenges: on the one hand, PVA lacks inherent photosensitive groups. If the traditional blending crosslinking agent mode is adopted, it will lead to the problem of phase separation, damaging the pore size uniformity of the membrane material; on the other hand, existing research mostly focuses on the improvement of single performance, lacking a systematic scheme for simultaneously optimizing ion conduction, anti-swelling and structural controllability.

[0005] A Chinese patent with the publication number CN109216632A and the application date of September 19, 2018 discloses a preparation method of a porous polyvinyl alcohol battery separator. By using a low-temperature method to inhibit the hydrogen bond interaction between polyvinyl alcohol hydroxyl groups, a high-porosity polyvinyl alcohol separator is obtained, which solves the problem that the pore size of the polyvinyl alcohol separator decreases or completely disappears due to hydrogen bond interaction during the preparation process. The prepared high-porosity polyvinyl alcohol separator has a larger pore size and better electrolyte compatibility. However, the high porosity and uneven pore structure of this membrane result in the defect of low tensile strength; a Chinese patent with the publication number CN119115268A and the application date of September 6, 2024 discloses a porous membrane and its preparation method and application. By using an ultraviolet laser light source with a shorter wavelength, higher light source absorption rate of the membrane material, and lower thermal effect for punching holes, a porous membrane with a smaller average pore size, higher surface flatness, and higher mechanical strength can be obtained. However, the laser punching treatment may cause a heat-affected zone on the membrane surface, which will have a negative impact on the performance of the membrane itself.

[0006] In summary, developing a PVA-based ion exchange membrane with high ionic conductivity, low swelling, excellent chemical and mechanical stability, and controllable pore size can not only promote the upgrading of PVA membranes in traditional fields such as fuel cells and water treatment, but also expand to emerging scenarios such as flexible electronics and intelligent sensing, which has important reference value, research significance, and considerable industrialization prospects in the field of ion exchange membrane materials technology. Summary of the Invention

[0007] To solve the problems existing in the prior art, the present invention discloses a bifunctional photo-controlled pore-forming ion exchange membrane and its preparation method and application. Using sulfonated polystyrene acetylene as a bifunctional modifier, the covalent grafting of sulfonic acid groups and the introduction of photosensitive double bonds are completed synchronously; combined with a mask lithography technique, through ultraviolet light selective curing and deionized water washing to remove the uncrosslinked area, precise control of the porous structure is achieved.

[0008] The technical solution of the present invention is as follows:

[0009] One of the purposes of the present invention is to provide a preparation method of a bifunctional photo-controlled pore-forming ion exchange membrane. Sulfonated polystyrene acetylene is grafted onto polyvinyl alcohol (PVA) through a low-temperature esterification reaction, and the sulfonic acid groups form a physical cross-linking network with PVA hydroxyl groups through hydrogen bond and ion-dipole interactions; then, reinforcing fillers are uniformly embedded in the PVA matrix, and a mixture of a photo-crosslinking agent and a photo-initiator is introduced to prepare a casting solution, so that the photosensitive double bonds of the polystyrene acetylene chain segments form a covalent network with the photo-crosslinking agent as side chains; combined with a porous mask to control the ultraviolet light irradiation area for selective photo-curing, and through water washing, through-hole channels are formed to prepare the PVA ion exchange membrane with controllable pore size.

[0010] Further, polyvinyl alcohol (PVA) with a degree of polymerization of 70-99% is completely dissolved in deionized water to prepare the PVA participating in the low-temperature esterification reaction.

[0011] Further, the mass ratio of polyvinyl alcohol (PVA) to sulfonated polystyrene acetylene is 5:1 to 10:1.

[0012] Further, the degree of polymerization of polyvinyl alcohol (PVA) is 80%.

[0013] Further, the low-temperature esterification reaction conditions are as follows: reacting for 2-12 h under acidic catalytic conditions at 10-12 °C in a stirring environment.

[0014] Further, the reinforcing filler is nanocellulose or carbon nanotubes, and the amount of the reinforcing filler is 3.1%-30% of the mass of PVA.

[0015] Further, the reinforcing filler is uniformly dispersed in the PVA matrix by ultrasonic dispersion. The ultrasonic temperature is 45 °C, the ultrasonic power is 160 W, and the dispersion time is 30-60 min.

[0016] Further, the photocrosslinking agent is acrylate, and its dosage is 5%-10% of the mass of polyvinyl alcohol (PVA); the photoinitiator is I2959, and its dosage is 0.1%-0.5% of the mass of polyvinyl alcohol (PVA).

[0017] Further, the dosage of the photocrosslinking agent is 5% of the mass of polyvinyl alcohol (PVA).

[0018] Further, the dosage of the photoinitiator is 0.1% of the mass of polyvinyl alcohol (PVA).

[0019] Further, the casting solution is uniformly coated on a glass plate or a PET film sheet, and the film thickness is adjusted. It is dried at 30-80 °C for 12-24 h, photocured and crosslinked under ultraviolet light according to an optional porous mask pattern for 90-120 s, and the uncrosslinked pore part is removed by washing with deionized water to obtain the polyvinyl alcohol (PVA) ion exchange membrane with controllable pore size.

[0020] Further, a film applicator is used to control the film thickness to be 20-30 μm.

[0021] The second object of the present invention is to provide a bifunctional light-controlled pore-forming ion exchange membrane.

[0022] The third object of the present invention is to provide an application of the bifunctional light-controlled pore-forming ion exchange membrane in fuel cells, flow batteries, and zinc-silver battery technologies.

[0023] Further, the application of the polyvinyl alcohol (PVA) ion exchange membrane in lithium-ion batteries, sodium-ion batteries, and zinc-ion batteries.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention innovatively combines "one-step" molecular design with lithography technology to achieve the efficient and controllable preparation of polyvinyl alcohol (PVA) ion exchange membranes. In traditional processes, the introduction of sulfonic acid groups and photosensitization need to be carried out step by step, which not only has a cumbersome process but also easily causes molecular chain breakage or uneven group distribution due to multiple chemical reactions. The present invention uses photosensitive sulfonated polystyrene acetylene as a bifunctional modifier to simultaneously complete the covalent grafting of sulfonic acid groups and the introduction of photosensitive double bonds in a single reaction step, simplifying the process and avoiding potential damage to the material structure caused by stepwise operations. In addition, through mask lithography technology, precise pore structure control is carried out on the ultraviolet light irradiation area, and the uncurable part forms through-hole channels after being washed with water, realizing the on-demand regulation of the porous structure and optimizing the ion transport path, breaking through the extensive management of pore size and porosity by traditional pore-forming technologies (such as phase separation and template method), and providing a new paradigm for the preparation of customized ion exchange membranes.

[0026] 2. In the bifunctional photo-controlled pore-forming ion exchange membrane of the present invention, the efficient grafting of sulfonic acid groups significantly enhances the ion exchange capacity of the membrane. The continuous distribution of hydrophilic groups and the dynamic physical cross-linking network cooperate to construct a low-resistance ion transport channel, enabling the ion conductivity to be improved by an order of magnitude compared with traditional PVA membranes. At the same time, the covalent network formed by photocrosslinking and the uniformly dispersed reinforcing fillers jointly strengthen the material skeleton, which can balance the mechanical strength and swelling inhibition, endowing the membrane with excellent mechanical strength and ion channel shape stability, and maintaining the structural integrity and performance stability even in high humidity or strong acid / alkali environments. In addition, the porous structure of the PVA ion exchange membrane can be flexibly regulated through mask patterns, realizing the precise design of pore size and porosity, so as to adapt to the different requirements of ion selectivity and flux in different application scenarios.

[0027] 3. The preparation method of the PVA ion exchange membrane of the present invention reflects green efficiency and wide applicability from process design to actual production. It not only reduces the energy consumption and equipment requirements of traditional processes through the one-step integration of bifunctional modifiers, but also avoids the use of organic solvents through the combination of an all-aqueous solvent system and room-temperature ultraviolet curing technology, meeting the development trend of green manufacturing, and providing reliable technical support for the industrial production and diversified applications of ion exchange membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the characteristic structure of the bifunctional photo-controlled pore-forming ion exchange membrane of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be further described below in conjunction with preferred embodiments. The provided embodiments are only for clarifying the present invention and not for limiting the scope of the present invention.

[0030] For the materials, reagents, etc. used in the following embodiments, unless otherwise specified, they can be obtained from commercial sources;

[0031] In the following quantitative tests of the embodiments, three independent repeated experiments are set, and the results are averaged;

[0032] For the experimental methods in the following embodiments, unless otherwise specified, they are all conventional methods;

[0033] Example 1

[0034] This example provides a preparation method of a bifunctional light-controlled pore-forming ion exchange membrane, including the following steps:

[0035] S1. Weigh 10 g of PVA with a degree of polymerization of 99% and add it to 100 mL of deionized water. Stir at 90 °C for 3 h until completely dissolved to obtain a uniform PVA solution;

[0036] S2. Add 1 g of sulfonated polystyrene acetylene to the PVA solution described in S1, and carry out a low-temperature esterification reaction for 2 h under a stirring environment at 12 °C with the addition of concentrated sulfuric acid as a catalyst;

[0037] S3. Under the conditions of 45 °C and 160 W, ultrasonically disperse 0.31 g of carbon nanotubes for 30 min to make them uniformly dispersed in the solution after the reaction in S2;

[0038] S4. Add 0.5 g of acrylate and 0.01 g of I2959 to the system, and stir evenly to obtain a casting solution;

[0039] S5. Uniformly coat the casting solution on a glass plate and adjust the membrane thickness. Dry at 80 °C for 12 h, and photocure and crosslink for 120 s under ultraviolet light according to an optional porous mask pattern. Wash with deionized water to remove the uncrosslinked pore part to obtain the bifunctional light-controlled pore-forming ion exchange membrane.

[0040] Example 2

[0041] This example provides a bifunctional light-controlled pore-forming ion exchange membrane, and its preparation method includes the following steps:

[0042] S1. Weigh 7 g of PVA with a degree of polymerization of 80% and add it to 100 mL of deionized water. Stir at 90 °C for 3 h until completely dissolved to obtain a uniform PVA solution;

[0043] S2. Add 1 g of sulfonated polystyrene acetylene to the PVA solution described in S1, and carry out a low-temperature esterification reaction for 7 h under a stirring environment at 11 °C with the addition of concentrated sulfuric acid as a catalyst;

[0044] S3. Ultrasonically disperse 1.05 g of nanocellulose at 45 °C under 160 W for 45 min to uniformly disperse it in the solution after the completion of the reaction in S2;

[0045] S4. Add 0.49 g of acrylate and 0.021 g of I2959 to the system, and stir evenly to obtain a casting solution;

[0046] S5. Uniformly coat the casting solution on a PET film sheet and adjust the film thickness. Dry it at 55 °C for 18 h, and photocure and crosslink it for 105 s according to an optional porous mask pattern under ultraviolet light. Wash it with deionized water to remove the uncrosslinked pore part to obtain the bifunctional light-controlled pore-forming ion exchange membrane.

[0047] Example 3

[0048] This example provides a method for preparing a bifunctional light-controlled pore-forming ion exchange membrane, including the following steps:

[0049] S1. Weigh 5 g of PVA with a polymerization degree of 70% and add it to 100 mL of deionized water. Stir at 90 °C for 3 h until completely dissolved to obtain a uniform PVA solution;

[0050] S2. Add 1 g of sulfonated polystyrene acetylene to the PVA solution described in S1, and carry out a low-temperature esterification reaction for 12 h under a stirring environment at 10 °C with concentrated sulfuric acid added dropwise as a catalyst;

[0051] S3. Ultrasonically disperse 1.5 g of carbon nanotubes at 45 °C under 160 W for 60 min to uniformly disperse them in the solution after the completion of the reaction in S2;

[0052] S4. Add 0.5 g of acrylate and 0.025 g of I2959 to the system, and stir evenly to obtain a casting solution;

[0053] S5. Uniformly coat the casting solution on a glass plate and adjust the film thickness. Dry it at 30 °C for 24 h, and photocure and crosslink it for 90 s according to an optional porous mask pattern under ultraviolet light. Wash it with deionized water to remove the uncrosslinked pore part to obtain the bifunctional light-controlled pore-forming ion exchange membrane.

[0054] The above are only the examples of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A method for preparing a dual-functional light-controlled pore-forming ion exchange membrane, characterized in that: Sulfonated polyphenylene vinylene is grafted onto polyvinyl alcohol (PVA) through a low-temperature esterification reaction, wherein the sulfonic acid groups react with the PVA hydroxyl groups through hydrogen bonds and ion-dipole interactions to form a physical cross-linking network; then, the reinforcing filler is uniformly embedded in the PVA matrix, and a mixture of a photocrosslinker and a photoinitiator is introduced to prepare a casting solution, so that the photosensitive double bonds of the polyphenylene vinylene segments serve as side chains to form a covalent network with the photocrosslinker; a porous mask is used to control the ultraviolet light irradiation area for selective photocuring, and through channels are formed after washing to obtain the polyvinyl alcohol (PVA) ion exchange membrane with controllable pore size.

2. The method for preparing a dual-functional light-controlled pore-forming ion exchange membrane according to claim 1, characterized in that: The polyvinyl alcohol PVA with a polymerization degree of 70-99% is completely dissolved in deionized water to obtain the polyvinyl alcohol PVA participating in the low-temperature esterification reaction.

3. The method for preparing a dual-functional light-controlled pore-forming ion exchange membrane according to claim 1, characterized in that: The mass ratio of polyvinyl alcohol (PVA) to sulfonated polyphenylene vinylene is 5:1 to 10:

1.

4. The method for preparing a dual-functional light-controlled pore-forming ion exchange membrane according to claim 1, characterized in that: The low-temperature esterification reaction conditions are to react for 2-12 hours under acidic catalytic conditions at 10-12° C. and stirring.

5. The method for preparing a dual-functional light-controlled pore-forming ion exchange membrane according to claim 1, characterized in that: The reinforcing filler is nanocellulose or carbon nanotube, and the reinforcing filler accounts for 3.1%-30% of the mass of PVA.

6. The method for preparing a dual-functional light-controlled pore-forming ion exchange membrane according to claim 5, characterized in that: The reinforcing filler is uniformly dispersed in the PVA matrix by ultrasonic dispersion, the ultrasonic temperature is 45° C., the ultrasonic power is 160 W, and the dispersion time is 30-60 min.

7. The method for preparing a dual-functional light-controlled pore-forming ion exchange membrane according to claim 1, characterized in that: The photocrosslinking agent is acrylate, and its usage is 5%-10% of the weight of polyvinyl alcohol (PVA); the photoinitiator is I2959, and its usage is 0.1%-0.5% of the weight of polyvinyl alcohol (PVA).

8. The method for preparing a dual-functional light-controlled pore-forming ion exchange membrane according to claim 1, characterized in that: The casting liquid is uniformly coated on a glass plate or a PET film and the film thickness is adjusted, dried at 30-80°C for 12-24 hours, photocured and cross-linked for 90-120 seconds under ultraviolet light according to an optional porous mask pattern, and the uncross-linked pores are removed by washing with deionized water to obtain the polyvinyl alcohol (PVA) ion exchange membrane with controllable pore size.

9. A dual-functional photo-controlled pore-forming ion exchange membrane prepared according to the method of any one of claims 1 to 8.

10. Use of the dual-functional photo-controlled pore-forming ion exchange membrane according to claim 9 in lithium ion batteries, sodium ion batteries, and zinc ion batteries.

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