A double side chain anion exchange membrane, its preparation method and application

Abstract

This invention relates to the field of polymer materials technology, and discloses a double-sided chain anion exchange membrane, its preparation method, and its applications. This invention provides a polyarylpiperidine polymer, which simultaneously introduces flexible (N-methylpiperidineonium) C2-C6 alkyl cationic chains and C7-C... 12 A straight-chain alkyl hydrophobic chain was successfully used to construct an ion conduction channel with a microphase separation structure. The double-side-chain anion exchange membrane prepared using this polymer as the membrane material has flexible cationic side chains that provide efficient ion transport sites. The ion conductivity can reach 134.6 mS / cm at 80℃, which meets the requirements of water electrolysis applications. The introduction of long alkyl hydrophobic chains significantly inhibits excessive water absorption and swelling of the membrane, with the swelling rate controlled within 50%, which greatly improves dimensional stability and mechanical strength. At the same time, the all-carbon chain polymer skeleton without ether bonds endows the membrane with excellent alkali resistance, and the conductivity loss rate is less than 20% after long-term operation under alkaline conditions.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a double-sided chain anion exchange membrane, its preparation method, and its application. Background Technology

[0002] With the increasing global demand for clean energy, hydrogen energy, as an efficient and clean energy carrier, has received widespread attention. Water electrolysis is one of the important pathways to achieve green hydrogen production. While proton exchange membrane electrolysis (PEMWE) technology boasts advantages such as high efficiency and high current density, its reliance on precious metal catalysts (such as platinum and iridium) and expensive perfluorosulfonic acid membranes results in high costs, limiting its large-scale application. Alkaline water electrolysis (ALK) technology, although lower in cost, uses highly concentrated alkaline electrolytes and suffers from slow reaction kinetics, limiting system efficiency and response speed.

[0003] In contrast, anion exchange membrane electrolysis (AEMWE) technology can utilize non-precious metal catalysts and operate under low-concentration alkaline or pure water conditions, offering greater economic efficiency and environmental friendliness. Therefore, AEMWE is considered one of the most promising next-generation water electrolysis technologies. However, as the core component of AEMWE, the anion exchange membrane (AEM) still faces numerous technical bottlenecks, including poor chemical stability and insufficient dimensional stability.

[0004] The chemical stability of anion exchange membranes (AEMs) is primarily limited by the alkali resistance of the polymer backbone and cationic groups. While commonly used polymer backbones in AEMs, such as polyphenylene oxide (PPO), polyetheretherketone (PEEK), and polyethersulfone (PES), possess certain mechanical properties and film-forming ability, their molecular chains generally contain aromatic ether bonds. Under high-temperature alkaline conditions, these bonds are susceptible to nucleophilic attack by hydroxide ions, leading to structural degradation and severely impacting the long-term stability of the membrane. The choice of cationic groups is equally crucial. Although quaternary ammonium salt cations are widely studied due to their ease of synthesis and low cost, their degradation mechanism under alkaline conditions remains a major factor limiting membrane stability. Furthermore, there is a typical trade-off between ionic conductivity and dimensional stability in AEMs: while high ion exchange capacity (IEC) is beneficial for improving conductivity, it often leads to excessive water absorption and severe swelling, thereby affecting mechanical strength and battery assembly stability.

[0005] Therefore, developing an anion exchange membrane that combines high ion conductivity, low swelling, high chemical stability, and simple preparation process is of great significance for promoting the development of hydrogen production technology through water electrolysis. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one object of the present invention is to provide a polyarylpiperidine polymer.

[0007] A second objective of this invention is to provide a method for preparing this polyarylepiperidine polymer.

[0008] The third objective of this invention is to provide a double-sided chain anion exchange membrane.

[0009] The fourth objective of this invention is to provide a method for preparing such a double-sided chain anion exchange membrane.

[0010] The fifth objective of this invention is to provide applications for this double-sided chain anion exchange membrane.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a polyarylpiperidine polymer having a structure as shown in formula (A) or formula (B): Formula (A); Formula (B); In formulas (A) and (B), R1 is independently selected from (N-methylpiperidinium) alkyl substituents, and the alkyl chain has 2-6 carbon atoms; R2 is independently selected from C7-C6. 12 Straight-chain alkyl; x is the molar degree of substitution of R1, y is the molar degree of substitution of R2, 0 < x < 100%, 0 < y < 100%, and x + y = 100%.

[0012] In some embodiments of the present invention, in formulas (A) and (B), R1 is independently selected from 2-(1-methylpiperidin-1-onth-1-yl)ethyl, 3-(1-methylpiperidin-1-onth-1-yl)propyl, 4-(1-methylpiperidin-1-onth-1-yl)butyl, 5-(1-methylpiperidin-1-onth-1-yl)pentyl or 6-(1-methylpiperidin-1-onth-1-yl)hexyl.

[0013] In some preferred embodiments of the present invention, in formulas (A) and (B), R1 is 6-(1-methylpiperidin-1-onthiol-1-yl)hexyl.

[0014] In some embodiments of the present invention, in formulas (A) and (B), R2 is independently selected from n-heptyl, n-octyl, or n-nonyl, respectively.

[0015] In some preferred embodiments of the present invention, in formulas (A) and (B), R2 is n-octyl.

[0016] In some preferred embodiments of the present invention, the molar substitution degree of R1 is x = 20%-40%, the molar substitution degree of R2 is 60%-80%, and x+y = 100%.

[0017] In some embodiments of the present invention, the number-average molecular weight of the polyarylepiperidine polymer is 50,000-800,000 Da.

[0018] A second aspect of the present invention provides a method for preparing the polyarylpiperidine polymer described in the first aspect of the present invention, comprising the following steps: S1. A polycondensation reaction is carried out between biphenyl monomers and 1-methyl-4-piperidinone in the presence of a composite catalyst of superacid and organic acid to obtain a polyarylpiperidine skeleton; under an inert atmosphere, a quaternization reaction is carried out between C2-C6 dihaloalkanes and 1-methylpiperidine to obtain ω-haloalkyl-N-methylpiperidine onium salt. In the presence of S2 and an acid-binding agent, the polyarylpiperidine skeleton is sequentially reacted with C7-C... 12 The quaternization grafting reaction of the halo-linear alkane and the ω-haloalkyl-N-methylpiperidine onium salt yields the polyarylpiperidine polymer.

[0019] In some embodiments of the present invention, step S1, in which the polyarylpiperidine skeleton is prepared, further includes the use of solvent I, wherein the solid-liquid ratio of the biphenyl monomer to solvent I is 1 g: (2.7-4.2) mL.

[0020] In some preferred embodiments of the present invention, in step S1, the polyarylpiperidine skeleton is prepared, and the solid-liquid ratio of the biphenyl monomer to solvent I is 1g: (3.1-3.8)mL.

[0021] In some embodiments of the present invention, in step S1, the solvent I used to prepare the polyarylpiperidine skeleton includes at least one of dichloromethane, chloroform, 1,2-dichloroethane, and nitromethane.

[0022] In some embodiments of the present invention, in step S1, the superacid and organic acid composite catalyst comprises trifluoromethanesulfonic acid and trifluoroacetic acid in a volume ratio of (10-13):1; the ratio of the biphenyl monomer, 1-methyl-4-piperidinone and the superacid and organic acid composite catalyst is (1.5-2.3)g: 1mL: (7-11)mL.

[0023] In some preferred embodiments of the present invention, in step S1, the superacid and organic acid composite catalyst comprises trifluoromethanesulfonic acid and trifluoroacetic acid in a volume ratio of (10-12):1; the ratio of the biphenyl monomer, 1-methyl-4-piperidinone and the superacid and organic acid composite catalyst is (1.7-2.1)g: 1mL: (8-10)mL.

[0024] In some embodiments of the present invention, in step S1, the biphenyl monomer is selected from diphenyl or para-terphenyl.

[0025] In some embodiments of the present invention, in step S1, the temperature of the polycondensation reaction is 0-10°C and the time is 5-12 hours.

[0026] In some preferred embodiments of the present invention, in step S1, the temperature of the polycondensation reaction is 0-5°C and the time is 5-6 hours.

[0027] In some embodiments of the present invention, in step S1, after the polyarylpiperidine skeleton is obtained and the polycondensation reaction is completed, the obtained mixture is placed in an alkaline solution, the precipitate is taken, cut into small pieces, filtered, washed, and dried to obtain the polyarylpiperidine skeleton.

[0028] In some embodiments of the present invention, in step S1, when the polyarylpiperidine skeleton is prepared, the concentration of the alkaline solution is 0.8-1.2 mol / L.

[0029] In some embodiments of the present invention, in step S1, the polyarylpiperidine skeleton is prepared, and the solute of the alkaline solution includes potassium hydroxide.

[0030] In some embodiments of the present invention, in step S1, the washing reagent includes deionized water and dichloromethane.

[0031] In some embodiments of the present invention, step S1, the preparation of ω-haloalkyl-N-methylpiperidine onium salt, further includes the use of solvent II, wherein the volume ratio of the C2-C6 dihaloalkane to solvent II is 1:(2.1-3.2); and the volume ratio of the 1-methylpiperidine to solvent II is 1:(4.3-6.6).

[0032] In some preferred embodiments of the present invention, in step S1, the volume ratio of the C2-C6 dihaloalkane to solvent II is 1:(2.4-2.9); and the volume ratio of 1-methylpiperidine to solvent II is 1:(4.9-6.0).

[0033] In some embodiments of the present invention, in step S1, the solvent II for preparing ω-haloalkyl-N-methylpiperidinium salt includes at least one of ethyl acetate, acetonitrile, acetone, ethanol, and tetrahydrofuran.

[0034] In some embodiments of the present invention, in step S1, the inert atmosphere includes nitrogen.

[0035] In some embodiments of the present invention, in step S1, the volume ratio of the C2-C6 dihaloalkane to 1-methylpiperidine is (5-7.5):1.

[0036] In some preferred embodiments of the present invention, in step S1, the volume ratio of the C2-C6 dihaloalkane to 1-methylpiperidine is (5.5-7.0):1.

[0037] In some embodiments of the present invention, in step S1, the C2-C6 dihaloalkane is selected from 1,2-dibromoethane, 1,3-dibromopropane, 1,4-dibromobutane, 1,5-dibromopentane, or 1,6-dibromohexane.

[0038] In some embodiments of the present invention, in step S1, the temperature of the quaternization reaction is 50-70°C and the time is 30-40 h.

[0039] In some preferred embodiments of the present invention, in step S1, the temperature of the quaternization reaction is 55-65°C and the time is 35-40h.

[0040] In some embodiments of the present invention, after the quaternization reaction is completed in step S1, the process further includes filtration, purification, and drying to obtain the ω-haloalkyl-N-methylpiperidinium salt.

[0041] In some embodiments of the present invention, in step S2, the mass ratio of the acid-binding agent to the polyarylpiperidine skeleton is 1:(1.8-2.8).

[0042] In some preferred embodiments of the present invention, in step S2, the mass ratio of the acid-binding agent to the polyarylpiperidine skeleton is 1:(2.1-2.6).

[0043] In some embodiments of the present invention, in step S2, the acid-binding agent includes potassium carbonate.

[0044] In some embodiments of the present invention, in step S2, the quaternization grafting reaction further includes the use of solvent III; the solid-liquid ratio of the polyarylpiperidine bone to solvent III is 1 g: (16.3-24.5) mL.

[0045] In some preferred embodiments of the present invention, in step S2, the solid-liquid ratio of the polyarylpiperidine bone to solvent III is 1 g: (18.3-22.5) mL.

[0046] In some embodiments of the present invention, in step S2, the solvent III includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, acetonitrile, acetone, and chloroform.

[0047] In some embodiments of the present invention, in step S2, the ω-haloalkyl-N-methylpiperidinium salt is dissolved in solvent IV and then participates in the quaternization grafting reaction.

[0048] In some embodiments of the present invention, in step S2, the solvent IV includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and sulfolane.

[0049] In some embodiments of the present invention, in step S2, C7-C 12 The halogenated straight-chain alkanes are selected from 1-bromoheptane, 1-bromooctane, or 1-bromononane.

[0050] In some embodiments of the present invention, in step S2, the temperature of the quaternization grafting reaction is 70-90°C and the time is 20-30h.

[0051] In some preferred embodiments of the present invention, in step S2, the temperature of the quaternization grafting reaction is 75-85°C and the time is 20-25h.

[0052] In some embodiments of the present invention, after the quaternization grafting reaction is completed in step S2, the solid product is collected by precipitation, washed, filtered, and dried to obtain the polyarylpiperidine polymer.

[0053] In some embodiments of the present invention, in step S2, the precipitate is prepared using ethyl acetate as a reagent.

[0054] A third aspect of the present invention provides a double-sided chain anion exchange membrane, wherein the membrane material of the double-sided chain anion exchange membrane is the polyarylpiperidine polymer described in the first aspect of the present invention.

[0055] In some embodiments of the present invention, the thickness of the double-sided chain anion exchange membrane is 10-50 µm.

[0056] In some embodiments of the present invention, the ionic conductivity of the double-sided chain anion exchange membrane at 80°C is 130-140 mS / cm.

[0057] A fourth aspect of the present invention provides a method for preparing the double-sided chain anion exchange membrane described in the third aspect of the present invention, comprising the following steps: The polyarylpiperidine polymer was dissolved and cast into a membrane. The product was then treated with an alkali solution to obtain the double-sided chain anion exchange membrane.

[0058] In some embodiments of the present invention, the solvent for dissolving the polyarylpiperidine polymer includes at least one of dimethyl sulfoxide, isopropanol, acetonitrile, acetone, and chloroform.

[0059] In some embodiments of the present invention, the concentration of the casting solution obtained by dissolving the polyarylpiperidine polymer is 2.4wt%-3.6wt%.

[0060] In some preferred embodiments of the present invention, the concentration of the casting solution obtained by dissolving the polyarylpiperidine polymer is 2.7wt%-3.3wt%.

[0061] In some embodiments of the present invention, the substrate for casting includes, but is not limited to, heat-resistant glass plates, steel plates, and polytetrafluoroethylene plates.

[0062] In some embodiments of the present invention, the alkaline treatment uses an alkaline solution with a concentration of 0.8-1.2 mol / L.

[0063] In some preferred embodiments of the present invention, the alkaline treatment uses an alkaline solution with a concentration of 0.9-1.1 mol / L.

[0064] In some embodiments of the present invention, the alkaline treatment uses an alkaline solution containing sodium hydroxide as the solute.

[0065] In some embodiments of the present invention, the alkaline treatment time is 20-50 hours.

[0066] In some preferred embodiments of the present invention, the alkaline treatment time is 24-48 hours.

[0067] The fifth aspect of the present invention provides the application of the double-side-chain anion exchange membrane described in the third aspect of the present invention in anion exchange membrane electrolysis of water.

[0068] The basic principles of this invention are explained as follows: 1) This invention utilizes a low-temperature polycondensation reaction between biphenyl monomers (diphenyl / paraphenyl) and 1-methyl-4-piperidinone under a composite catalytic system of superacid and organic acid to form a polyarylpiperidine conjugated backbone without ether bonds. This backbone has a pure carbon-carbon conjugated structure and is not easily reacted with OH groups in an alkaline environment. - The nucleophilic attack of the aryl ether bond (COC) avoids skeletal degradation under alkaline conditions from a molecular structure perspective. At the same time, the heterocyclic structure of the piperidine ring has low ring strain characteristics, which can inhibit the elimination / substitution degradation of the cationic group after quaternization. This provides double protection for the long-term chemical stability of the membrane in high-concentration alkaline solutions. 2) Through quaternization grafting reaction, (N-methylpiperidinium) C2-C6 alkyl hydrophilic cationic chains and C7-C are sequentially introduced onto the active sites of the benzene ring in the main chain. 12 A straight-chain alkyl hydrophobic chain with complementary grafting of two side chains in a non-zero ratio, wherein the hydrophilic cationic chain acts as the OH group. -The core site for ion transport, the (N-methylpiperidinium) quaternary ammonium cation, possesses high ion dissociation. Furthermore, the flexible C2-C6 alkyl chain keeps the cation groups away from the main chain, enhancing the cation's freedom and mobility, facilitating the formation of continuous ion transport channels. The long, hydrophobic alkyl chain acts as a structural barrier to inhibit swelling. (C7-C...) 12 The hydrophobic properties of long straight-chain alkyl groups form hydrophobic microdomains, which physically block the hydrophilic microdomains of hydrophilic cationic chains, limiting the excessive permeation of water molecules in the membrane and effectively inhibiting the swelling of the membrane in aqueous solution. At the same time, the steric hindrance of the hydrophobic chains can further protect the main chain and cationic groups, improving alkali resistance stability. 3) Due to the chemical differences between hydrophilic and hydrophobic chains, they spontaneously form nanoscale hydrophilic-hydrophobic microphase separation structures within the membrane. These hydrophilic microregions are interconnected, forming continuous ion transport channels, significantly reducing OH- ions. - The transport resistance is reduced, the ionic conductivity is improved, and the hydrophobic microphase forms a rigid supporting framework, which not only ensures the mechanical strength of the membrane, but also further restricts the swelling and deformation of the membrane, so that the membrane can maintain excellent dimensional stability even under high water absorption. By controlling the molar substitution degree of hydrophilic cationic chains and long alkyl hydrophobic chains, the microphase separation structure can be precisely controlled, so that the continuity of ion transport channels and the dimensional stability of the membrane can be optimally balanced.

[0069] Compared with the prior art, the beneficial effects of the present invention are: The polyarylpiperidine polymer provided by this invention introduces flexible (N-methylpiperidine) C2-C6 alkyl cationic chains and C7-C6 alkyl cationic chains simultaneously onto the ether-free polyarylpiperidine backbone. 12 A straight-chain alkyl hydrophobic chain was successfully used to construct an ion conduction channel with a microphase separation structure. A double-side-chain anion exchange membrane prepared using this polymer as the membrane material features flexible cationic side chains that provide highly efficient ion transport sites. The ion conductivity reaches 134.6 mS / cm at 80℃, meeting the requirements for water electrolysis applications. The introduction of long alkyl hydrophobic chains significantly inhibits excessive water absorption and swelling of the membrane, keeping the swelling rate below 50%, thus greatly improving dimensional stability and mechanical strength. Simultaneously, the all-carbon polymer skeleton without ether bonds endows the membrane with excellent alkali resistance, with a conductivity loss rate of less than 20% after long-term operation under alkaline conditions. The polyarylpiperidine polymer preparation process provided by this invention is simple and low-cost, and the resulting anion exchange membrane exhibits excellent comprehensive performance, showing broad application prospects in the field of anion exchange membrane water electrolysis. Attached Figure Description

[0070] Figure 1 This is a schematic diagram of the synthetic route of the polyarylpiperidine polymer in Example 1; Figure 2 This is a schematic diagram of the synthetic route of the polyarylepiperidine polymer in Example 2; Figure 3 This is a schematic diagram of the synthetic route of the polyarylepiperidine polymer in Comparative Example 1; Figure 4 The 1H NMR spectrum of the polyarylpiperidine polymer in Example 1; Figure 5 The 1H NMR spectrum of the polyarylpiperidine polymer in Example 2; Figure 6 The 1H NMR spectrum of the polyarylepiperidine polymer in Comparative Example 1 is shown. Figure 7 Thermogravimetric curves of the anion exchange membranes in Examples 1, 2 and Comparative Example 1; Figure 8 The ionic conductivity of the anion exchange membranes in Examples 1, 2 and Comparative Example 1 Temperature change graph; Figure 9 The graph shows the swelling ratio-temperature variation of the anion exchange membranes in Examples 1, 2 and Comparative Example 1. Figure 10 This is a comparison diagram of the long-term alkali resistance of the anion exchange membranes in Examples 1 and 2 and Comparative Example 1; Figure 11 This is an atomic force microscopy phase diagram of the anion exchange membrane in Example 2; Figure 12 The image shows the atomic force microscopy phase diagram of the anion exchange membrane in Comparative Example 1. Detailed Implementation

[0071] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0072] Example 1 This embodiment prepares a polyarylpiperidine polymer with the structure shown in formula (a), and the preparation steps are as follows: Figure 1 As shown, a double-side-chain anion exchange membrane was prepared using this polyarylepiperidine polymer as the membrane material: Equation (a) Preparation of polyarylpiperidine polymers: S11. Dissolve 2.30 g (10 mmol) of terphenyl in 8 mL of dichloromethane. Place the resulting solution in an ice-water bath at 0 °C. Add 1.22 mL of 1-methyl-4-piperidinone and mix well. Then add a composite catalyst of trifluoromethanesulfonic acid (10 mL) and trifluoroacetic acid (1 mL). React at 0 °C for 5-6 h to obtain a purplish-black viscous liquid. Add the obtained viscous liquid to a 1 mol / L KOH aqueous solution to precipitate a white hard solid. Cut the solid into small pieces, filter, wash thoroughly with deionized water, wash with dichloromethane, and dry to obtain a polyarylpiperidine skeleton. S12. Add 1,6-dibromohexane (11.37 mL) and ethyl acetate (30 mL) to a round-bottom flask, purge with nitrogen, and stir thoroughly. Dissolve 1-methylpiperidine (1.83 mL) in 10 mL of ethyl acetate, and slowly add the resulting solution dropwise to the flask. React at 60 °C for 36 h to obtain a white solid precipitate. Filter, purify with ethyl acetate to remove excess reactants, and dry to obtain 1-(6-bromohexyl)-1-methylpiperidine. S21. Dissolve the polyarylpiperidine skeleton (0.98 g) in dimethyl sulfoxide (20 mL). After the polymer is completely dissolved, add anhydrous potassium carbonate (0.42 g) and continue stirring. Then, first add 1-bromooctane (70% molar substitution of n-octyl), and then add 1-(6-bromohexyl)-1-methylpiperidine (30% molar substitution of 6-(1-methylpiperidine-1-onthio-1-yl)hexyl) dissolved in dimethyl sulfoxide. The quaternization grafting reaction is carried out at 80 °C. After reacting for 24 h, the solution is precipitated in ethyl acetate. The crude product is washed several times with deionized water, filtered, and dried to obtain the polyarylpiperidine polymer, denoted as PTP-Pip-30%.

[0073] Preparation of double-sided chain anion exchange membranes: The polyarylpiperidine polymer PTP-Pip-30% was dissolved in dimethyl sulfoxide to prepare a casting solution with a concentration of 3wt%. The casting solution was cast or cast onto a heat-resistant glass plate and dried in a vacuum oven at 60°C for 24 hours. After the solvent had completely evaporated, the glass plate was immersed in deionized water and allowed to stand for a period of time before being peeled off. The resulting product was soaked in a 1mol / L NaOH aqueous solution for 48 hours to obtain a double-sided chain anion exchange membrane, denoted as PTP-Pip-30%-OH.

[0074] Example 2 This embodiment prepares a polyarylpiperidine polymer with the structure shown in formula (b), and the preparation steps are as follows. Figure 2 As shown, a double-side-chain anion exchange membrane was prepared using this polyarylepiperidine polymer as the membrane material: Formula (b) Preparation of polyarylpiperidine polymers: S11. Dissolve 2.30 g (10 mmol) of terphenyl in 8 mL of dichloromethane. Place the resulting solution in an ice-water bath at 0 °C. Add 1.22 mL of 1-methyl-4-piperidinone and mix well. Then add a composite catalyst of trifluoromethanesulfonic acid (10 mL) and trifluoroacetic acid (1 mL). React at 0 °C for 5-6 h to obtain a purplish-black viscous liquid. Add the obtained viscous liquid to a 1 mol / L KOH aqueous solution to precipitate a white hard solid. Cut the solid into small pieces, filter, wash thoroughly with deionized water, wash with dichloromethane, and dry to obtain a polyarylpiperidine skeleton. S12. Add 1,6-dibromohexane (11.37 mL) and ethyl acetate (30 mL) to a round-bottom flask, purge with nitrogen, and stir thoroughly. Dissolve 1-methylpiperidine (1.83 mL) in 10 mL of ethyl acetate, and slowly add the resulting solution dropwise to the flask. React at 60 °C for 36 h to obtain a white solid precipitate. Filter, purify with ethyl acetate to remove excess reactants, and dry to obtain 1-(6-bromohexyl)-1-methylpiperidine. S21. Dissolve the polyarylpiperidine skeleton (0.98 g) in dimethyl sulfoxide (20 mL). After the polymer is completely dissolved, add anhydrous potassium carbonate (0.42 g) and continue stirring. Then, first add 1-bromooctane (30% molar substitution of n-octyl), and then add 1-(6-bromohexyl)-1-methylpiperidine (70% molar substitution of 6-(1-methylpiperidine-1-onthio-1-yl)hexyl) dissolved in dimethyl sulfoxide. The quaternization grafting reaction is carried out at 80 °C. After reacting for 24 h, the solution is precipitated in ethyl acetate. The crude product is washed several times with deionized water, filtered, and dried to obtain the polyarylpiperidine polymer, denoted as PTP-Pip-70%.

[0075] Preparation of double-sided chain anion exchange membranes: The polyarylpiperidine polymer PTP-Pip-70% was dissolved in dimethyl sulfoxide to prepare a casting solution with a concentration of 3wt%. The casting solution was cast or cast onto a heat-resistant glass plate and dried in a vacuum oven at 60°C for 24 hours. After the solvent had completely evaporated, the glass plate was immersed in deionized water and allowed to stand for a period of time before being peeled off. The resulting product was soaked in a 1mol / L NaOH aqueous solution for 48 hours to obtain a double-sided chain anion exchange membrane, denoted as PTP-Pip-70%-OH.

[0076] Comparative Example 1 This comparative example prepares a polyarylpiperidine polymer with the structure shown in formula (c), and the preparation steps are as follows. Figure 3 As shown, an anion exchange membrane was prepared using this polyarylepiperidine polymer as the membrane material: Formula (c) Preparation of polyarylpiperidine polymers: S11. Dissolve 2.30 g (10 mmol) of terphenyl in 8 mL of dichloromethane. Place the resulting solution in an ice-water bath at 0 °C. Add 1.22 mL of 1-methyl-4-piperidinone and mix well. Then add a composite catalyst of trifluoromethanesulfonic acid (10 mL) and trifluoroacetic acid (1 mL). React at 0 °C for 5-6 h to obtain a purplish-black viscous liquid. Add the obtained viscous liquid to a 1 mol / L KOH aqueous solution to precipitate a white hard solid. Cut the solid into small pieces, filter, wash thoroughly with deionized water, wash with dichloromethane, and dry to obtain a polyarylpiperidine skeleton. S12. Add 1,6-dibromohexane (11.37 mL) and ethyl acetate (30 mL) to a round-bottom flask, purge with nitrogen, and stir thoroughly. Dissolve 1-methylpiperidine (1.83 mL) in 10 mL of ethyl acetate, and slowly add the resulting solution dropwise to the flask. React at 60 °C for 36 h to obtain a white solid precipitate. Filter, purify with ethyl acetate to remove excess reactants, and dry to obtain 1-(6-bromohexyl)-1-methylpiperidine. S21. Dissolve the polyarylpiperidine skeleton (0.98 g) in dimethyl sulfoxide (20 mL). After the polymer is completely dissolved, add anhydrous potassium carbonate (0.42 g) and continue stirring. Then add 1-bromooctane (100% molar substitution of n-octyl) and carry out a quaternization grafting reaction at 80 °C. After reacting for 24 h, precipitate the solution in ethyl acetate. After washing the crude product several times with deionized water, filter and dry to obtain the polyarylpiperidine polymer, denoted as PTP-Pip-0.

[0077] Preparation of anion exchange membranes: The polyarylpiperidine polymer PTP-Pip-100% was dissolved in dimethyl sulfoxide to prepare a casting solution with a concentration of 3wt%. The casting solution was cast or cast onto a heat-resistant glass plate and dried in a vacuum oven at 60°C for 24 hours. After the solvent had completely evaporated, the glass plate was immersed in deionized water and allowed to stand for a period of time before being peeled off. The resulting product was soaked in a 1mol / L NaOH aqueous solution for 48 hours to obtain an anion exchange membrane, denoted as PTP-Pip-0%-OH.

[0078] Characterization and performance testing 1. The polyarylpiperidine polymers prepared in Examples 1, 2 and Comparative Example 1 were characterized using nuclear magnetic resonance spectroscopy (Bruker AV400, 400MHz) at a resonance frequency of 400MHz: Figure 4 The image shows the 1H NMR spectrum of the polyarylpiperidine polymer in Example 1. Figure 5 The image shows the 1H NMR spectrum of the polyarylpiperidine polymer in Example 2. Figure 6 The image shows the 1H NMR spectrum of the polyarylpiperidine polymer in Comparative Example 1.Figures 4-6 It can be seen that the 1H NMR spectrum of the polyarylpiperidine polymer in Comparative Example 1 shows the characteristic hydrogen peaks of the benzene ring of the polyarylpiperidine main chain (6.0-8.0 ppm), the aliphatic hydrogen peaks of the piperidine ring (2.0-4.0 ppm), and the alkyl hydrogen peaks of the n-octyl hydrophobic chain (0.5-2.0 ppm). All three types of characteristic peaks are present, proving that the hydrophobic chain was successfully grafted onto the active site of the benzene ring of the main chain. The spectrum does not show the characteristic hydrogen peaks of the 6-(1-methylpiperidin-1-onthium-1-yl)hexyl cationic chain, indicating that the compound is a purely hydrophobic graft, consistent with the experimental design. The 1H NMR spectrum of the polyarylpiperidine polymer in Example 1, compared to Comparative Example 1, adds the characteristic hydrogen peaks of the 6-(1-methylpiperidin-1-onthium-1-yl)hexyl cationic chain (3.5-4.5 ppm). The 1ppm NMR spectrum of the polyarylpiperidine polymer in Example 2 is similar to that in Example 1. Compared to Example 1, the integral area of ​​the characteristic hydrogen peak of the 6-(1-methylpiperidin-1-onthium-1-yl)hexyl cationic chain (3.5-4.5ppm) is increased, while the integral area of ​​the alkyl hydrogen peak of the n-octyl hydrophobic chain (0.5-2.0ppm) is decreased, with an integral area ratio of approximately 7:3. The above results indicate that the polyarylpiperidine polymers PTP-Pip-30%, PTP-Pip-70%, and PTP-Pip-0% were successfully prepared. The method provided by this invention has the ability to precisely control the side-linking ratio, and the characteristic hydrogen peak shape and shift of the benzene ring in the polyarylpiperidine main chain remain unchanged, proving that the bilateral linking reaction did not damage the main chain and the main chain structure is intact.

[0079] 2. The thermal stability of the polyarylene piperidine polymers prepared in Examples 1, 2 and Comparative Example 1 was tested using a Netzsch TG 209 F3 thermogravimetric analyzer. Before testing, the samples were dried at 80°C for 24 hours. During the test, the heating rate was set to 10°C / min, and the temperature range was 30-800°C. Figure 7 The thermogravimetric curves of the anion exchange membranes in Examples 1, 2 and Comparative Example 1 are obtained from... Figure 7 It can be seen that the thermogravimetric processes of the anion exchange membranes PTP-Pip-30%-OH, PTP-Pip-70%-OH, and PTP-Pip-0%-OH all consist of three stages: the first stage occurs at 150°C. The first stage, around 250℃, is caused by the decomposition of the n-octyl side chain, with a weight loss rate of <10%. This is the pyrolysis of small molecule alkyl side chains and does not affect the core structure of the membrane. The second stage, around 380-450℃, is caused by the decomposition of the piperidine cation of the 6-(1-methylpiperidin-1-onth-1-yl)hexyl side chain, with a weight loss rate of about 20%-30%. This is the pyrolysis of ion transport sites. This temperature is much higher than the operating temperature of alkaline water electrolysis (60-80℃). The 6-(1-methylpiperidin-1-onth-1-yl)hexyl molar substitution degree of the anion exchange membrane prepared in Comparative Example 1 is 0%, so the weight loss in this stage is not significant. The third stage is above 470℃, corresponding to the decomposition of the polyarylpiperidine skeleton. The above results show that the anion exchange membranes prepared in Examples 1-3 of this invention all have good thermal stability, with a main chain thermal decomposition temperature >470℃, which is much higher than the working temperature of alkaline water electrolysis of 60-80℃, fully meeting the thermal stability requirements for industrial applications. Furthermore, the side link graft ratio has no negative impact on the thermal stability of the membrane, and the membrane has strong process adaptability.

[0080] 3. The hydroxide conductivity of the anion exchange membranes in Examples 1, 2 and Comparative Example 1 was tested using a four-electrode AC impedance method (CHI 660) in an electrochemical working state, with a frequency range of 1 MHz to 1 Hz. Figure 8 The ionic conductivity of the anion exchange membranes in Examples 1, 2 and Comparative Example 1 Temperature change graph, from Figure 8 It can be seen that the ionic conductivity of the anion exchange membranes PTP-Pip-30%-OH, PTP-Pip-70%-OH, and PTP-Pip-0%-OH all increased significantly with increasing temperature. This is because increasing temperature intensifies the movement of molecular chains within the membrane, increases the permeation of water molecules, and makes the ion transport channels more open, thus increasing the OH- ion conductivity. - The increased migration rate conforms to the conventional conductivity variation pattern of anion exchange membranes. Specifically, the conductivity at 80℃ for PTP-Pip-30%-OH, PTP-Pip-70%-OH, and PTP-Pip-0%-OH are 134.6 mS / cm, 130.9 mS / cm, and 102.2 mS / cm, respectively, all meeting the conductivity requirements of anion exchange membranes in current water electrolysis cells. The highest conductivity at 80℃ for PTP-Pip-30%-OH indicates that the 30% molar substitution of the 6-(1-methylpiperidin-1-onthiol-1-yl)hexyl group provides sufficient ion transport sites, while the 70% molar substitution of the n-octyl group forms dense hydrophobic microdomains. This substitution condition allows the hydrophilic microdomains to interconnect, forming continuous and efficient ion transport channels with minimal transport resistance.

[0081] 4. Swelling tests were conducted on the anion exchange membranes in Examples 1, 2, and Comparative Example 1. The anion exchange membranes were cut into square samples (2cm × 2cm) and immersed in deionized water at a constant temperature for 24 hours. After removal, the residual liquid on the surface was quickly wiped off with filter paper. The side length of the sample was measured, and the average value was recorded as L1. Subsequently, the membrane samples were completely dried, and the side length of the sample in the dry membrane state was measured and the average value was recorded as L2. The swelling rate SR was calculated using the formula: SR = (L1 - L2) / L1 × 100%. Figure 9 The swelling ratio of the anion exchange membranes in Examples 1, 2 and Comparative Example 1. Temperature change, by Figure 9 It can be seen that the swelling ratios of the anion exchange membranes PTP-Pip-30%-OH, PTP-Pip-70%-OH, and PTP-Pip-0%-OH all increase slowly with increasing temperature, but the overall increase is small, proving that the membranes have excellent dimensional stability and that temperature changes have little impact on the membrane structure. Under the same temperature conditions, the swelling ratios of the anion exchange membranes show a trend of PTP-Pip-0%-OH < PTP-Pip-30%-OH < PTP-Pip-70%-OH, indicating that when the molar substitution degree of 6-(1-methylpiperidin-1-onthiol-1-yl)hexyl is 30% and the molar substitution degree of n-octyl is 70%, the optimal balance between high conductivity and low swelling ratio is achieved.

[0082] 5. The anion exchange membranes from Examples 1, 2, and Comparative Example 1 were immersed in 3 mol / L NaOH aqueous solution for 1 week, 2 weeks, 1 month, and 2 months, respectively. The ionic conductivity at different immersion times was tested using the four-electrode AC impedance method of an electrochemical workpiece (CHI 660), and the conductivity loss rate was calculated to characterize the long-term chemical stability of the membranes in high-concentration alkaline solutions. Figure 10 This is a comparison chart of the long-term alkali resistance of the anion exchange membranes in Examples 1 and 2 and Comparative Example 1. Figure 10 It can be seen that the conductivity loss rate of the anion exchange membranes PTP-Pip-30%-OH, PTP-Pip-70%-OH and PTP-Pip-0%-OH all increased slowly with the extension of soaking time, but the overall loss rate was extremely low. After soaking for 1 month, the loss rate was ≤20%, which proves that the anion exchange membrane has excellent long-term alkali resistance in high concentration alkaline solution. After soaking for 2 months, the loss rate increased slightly, but was still <30%, and the main chain and side chain did not undergo significant degradation.

[0083] 6. The microphase separation structure of the anion exchange membranes in Example 2 and Comparative Example 1 was characterized using an SPI3800N atomic force microscope (AFM). The test mode was knocking mode, and the test range was 500 nm × 500 nm. The surface morphology was recorded. The bright and dark phase regions corresponded to hydrophobic microregions (bright regions) and hydrophilic microregions (dark regions), respectively. The phase region distribution reflects the morphology of the ion transport channels within the membrane. Figure 11 This is an atomic force microscopy phase image of the anion exchange membrane in Example 2. Figure 12 The atomic force microscopy (AFM) phase diagram of the anion exchange membrane in Comparative Example 1 shows a predominance of large, continuous bright areas (hydrophobic microregions) with only a few scattered, tiny dark areas (hydrophilic microregions). These hydrophilic microregions are dispersed and unconnected, failing to form continuous ion transport channels, resulting in lower ion conductivity but optimal dimensional stability. In Example 2, the AFM phase diagram of the anion exchange membrane shows a predominance of large dark areas (hydrophilic microregions), with bright areas (hydrophobic microregions) dispersed as tiny islands within the hydrophilic microregions. These hydrophilic microregions form a continuous phase network, but their irregular morphology and uneven pore size result in disordered and dispersed ion transport channels. Figure 8 and Figure 9 The performance of the anion exchange membrane PTP-Pip-30%-OH was studied, and the optimal microphase separation structure of the membrane with 30% cation chains and 70% hydrophobic chains, which forms continuous and ordered hydrophilic microdomains and dense and uniform hydrophobic microdomains, was derived, providing structural support for high conductivity and low swelling rate.

Claims

1. A polyarylpiperidine polymer, characterized in that, Its structure is shown in equation (A) or equation (B): Formula (A); Formula (B); In formulas (A) and (B), R1 is independently selected from (N-methylpiperidinium) alkyl substituents, and the alkyl chain has 2-6 carbon atoms; R2 is independently selected from C7-C6. 12 Straight-chain alkyl; x is the molar degree of substitution of R1, y is the molar degree of substitution of R2, 0 < x < 100%, 0 < y < 100%, and x + y = 100%.

2. The polyarylpiperidine polymer according to claim 1, characterized in that, In formulas (A) and (B), R1 is independently selected from 2-(1-methylpiperidin-1-onth-1-yl)ethyl, 3-(1-methylpiperidin-1-onth-1-yl)propyl, 4-(1-methylpiperidin-1-onth-1-yl)butyl, 5-(1-methylpiperidin-1-onth-1-yl)pentyl or 6-(1-methylpiperidin-1-onth-1-yl)hexyl; And / or, the R2 is independently selected from n-heptyl, n-octyl or n-nonyl.

3. The polyarylpiperidine polymer according to claim 2, characterized in that, The number-average molecular weight of the polyarylepiperidine polymer is 50,000-800,000 Da.

4. The method for preparing the polyarylpiperidine polymer according to any one of claims 1-3, characterized in that, Includes the following steps: S1. A polycondensation reaction is carried out between biphenyl monomers and 1-methyl-4-piperidinone in the presence of a composite catalyst of superacid and organic acid to obtain a polyarylpiperidine skeleton; under an inert atmosphere, a quaternization reaction is carried out between C2-C6 dihaloalkanes and 1-methylpiperidine to obtain ω-haloalkyl-N-methylpiperidine onium salt. In the presence of S2 and an acid-binding agent, the polyarylpiperidine skeleton is sequentially reacted with C7-C... 12 The quaternization grafting reaction of the halo-linear alkane and the ω-haloalkyl-N-methylpiperidine onium salt yields the polyarylpiperidine polymer.

5. The method for preparing the polyarylpiperidine polymer according to claim 4, characterized in that, In step S1, the superacid and organic acid composite catalyst comprises trifluoromethanesulfonic acid and trifluoroacetic acid in a volume ratio of (10-13):1; the ratio of the biphenyl monomer, 1-methyl-4-piperidinone and the superacid and organic acid composite catalyst is (1.5-2.3)g: 1mL: (7-11)mL. And / or, in step S1, the volume ratio of the C2-C6 dihaloalkane to 1-methylpiperidine is (5-7.5):

1.

6. The method for preparing the polyarylpiperidine polymer according to claim 4, characterized in that, In step S1, the temperature of the polycondensation reaction is 0-10℃ and the time is 5-12h; And / or, in step S1, the quaternization reaction is carried out at a temperature of 50-70°C for a time of 30-40 hours; And / or, in step S2, the temperature of the quaternization grafting reaction is 70-90℃ and the time is 20-30h.

7. The method for preparing the polyarylpiperidine polymer according to claim 4, characterized in that, In step S1, the biphenyl monomer is selected from diphenyl or para-terphenyl; And / or, in step S1, the C2-C6 dihaloalkane is selected from 1,2-dibromoethane, 1,3-dibromopropane, 1,4-dibromobutane, 1,5-dibromopentane, or 1,6-dibromohexane; And / or, in step S2, the C7-C 12 The halogenated straight-chain alkanes are selected from 1-bromoheptane, 1-bromooctane, or 1-bromononane.

8. A double-sided chain anion exchange membrane, characterized in that, The membrane material of the double-sided chain anion exchange membrane is the polyarylpiperidine polymer as described in any one of claims 1-3.

9. The method for preparing the double-sided chain anion exchange membrane according to claim 8, characterized in that, Includes the following steps: The polyarylpiperidine polymer was dissolved and cast into a membrane. The product was then treated with an alkali solution to obtain the double-sided chain anion exchange membrane.

10. The application of the double-sided chain anion exchange membrane according to claim 8 in anion exchange membrane electrolysis of water.

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