Alkali-resistant anion-exchange membrane based on fluorine-substituted overhanging structure polyarylmethylpiperidine and preparation method of alkali-resistant anion-exchange membrane

Abstract

The invention relates to the technical field of anion exchange membranes, in particular to an alkali-resistant anion exchange membrane based on fluorine-substituted overhang structure polyarylmethylpiperidine and a preparation method of the alkali-resistant anion exchange membrane based on fluorine-substituted overhang structure polyarylmethylpiperidine. The anion exchange membrane is prepared from a piperidine polymer and an E-51 cross-linking agent through a cross-linking reaction; the piperidine polymer is obtained by modifying a polyarylmethyl polymer through 4-methylpiperidine, and the dosage of the 4-methylpiperidine is 1.0 eq to 1.5 eq relative to a benzyl chloride group in the polyarylmethyl polymer; according to the invention, a fluorine-substituted pendent benzyl aromatic ring structure is designed, the strong electronegativity of fluorine atoms can enhance the molecular polarity, and formation of a continuous hydrophilic micro-region in a polymer matrix is promoted; meanwhile, a suspension structure enables a cationic group to be far away from a polymer main chain, so that the limitation of main chain steric hindrance on ion movement is reduced, and the hydroxyl ion conduction efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of anion exchange membranes, in particular to an alkali-resistant anion exchange membrane based on a fluorine-substituted pendant structure polyaromatic methyl piperidine and a preparation method. BACKGROUND

[0002] As a core component of alkali energy devices (such as alkaline fuel cells and alkaline electrolytic cells), the performance of an anion exchange membrane directly determines the energy conversion efficiency, operation stability and service life of the device. An ideal anion exchange membrane should have high ion conductivity, excellent alkali resistance and good mechanical properties to meet the long-term operation requirements of the device under high alkali concentration and certain temperature.

[0003] However, the existing anion exchange membranes generally have the following key problems: insufficient ion conductivity, uneven distribution of cation groups such as quaternary ammonium salt groups in most anion exchange membranes, and poor compatibility between the polymer matrix and the ion groups, which makes it difficult to form a continuous and unobstructed ion transmission channel, resulting in low hydroxyl ion conductivity, especially under medium and low temperature conditions, which restricts the output performance of the device; poor alkali resistance, in a high-concentration alkali solution and a certain temperature environment, traditional quaternary ammonium salt cations are prone to Hofmann elimination, nucleophilic substitution and other degradation reactions, and the polymer main chain, such as polyaromatic ether, is easily attacked by hydroxyl groups to cause chain scission, resulting in a decrease in ion exchange capacity of the membrane and structural damage, and the service life is usually less than 500 hours; the mechanical properties and the swelling degree are difficult to balance, in order to improve the ion conductivity, more cation groups need to be introduced, but excessive ion groups will increase the hydrophilicity of the membrane, leading to high water absorption rate and serious swelling of the membrane in water, and further causing a decrease in mechanical strength and poor dimensional stability, and even causing the problem of separation of the membrane from the electrode; if the ion groups are reduced or the crosslinking degree is increased to improve the mechanical properties, the ion conductivity will be further reduced, forming a contradiction between “conductivity and mechanical properties”.

[0004] Structural design limitations: the existing anion exchange membranes mostly adopt a structure of main chain branched cation groups, the cation groups are close to the main chain and are difficult to move freely due to the influence of the spatial steric hindrance of the main chain, and the degradation of the main chain will directly cause the cation groups to fall off; some membranes introduce fluorine elements to improve stability, but the fluorine substitution position is mostly concentrated in the main chain, and the optimization effect on the ion transmission channel is limited, and the polarity and spatial steric hindrance advantages of fluorine elements cannot be fully utilized.

[0005] Therefore, developing an anion exchange membrane with high ion conductivity, excellent alkali resistance and good mechanical properties has become a key technical bottleneck for promoting the industrial application of alkali energy devices. SUMMARY

[0006] The application aims to solve the problems of low ion conductivity, poor chemical stability and mechanical performance of existing anion exchange membranes, and provides an alkali-resistant anion exchange membrane based on fluorine-substituted pendant structure polyaromatic methyl piperidine and a preparation method.

[0007] An alkali-resistant anion exchange membrane based on fluorine-substituted pendant structure polyaromatic methyl piperidine, wherein the anion exchange membrane is prepared by cross-linking reaction of piperidyl polymer and E-51 cross-linking agent;

[0008] The piperidyl polymer is obtained by modifying polyaromatic methyl polymer with 4-methyl piperidine, and the amount of 4-methyl piperidine is 1.0 eq-1.5 eq relative to the benzyl chloride group in the polyaromatic methyl polymer;

[0009] The polyaromatic methyl polymer is formed by polymerization of fluorine-substituted polyaromatic methyl monomer and bisphenol A diglycidyl ether under the initiation of azobisisobutyronitrile, and the molar ratio of the fluorine-substituted polyaromatic methyl monomer to bisphenol A diglycidyl ether is 8:2, the amount of azobisisobutyronitrile is 0.1 mmol, and corresponds to the total amount of 8 mmol of fluorine-substituted polyaromatic methyl monomer and 2 mmol of bisphenol A diglycidyl ether, the number average molecular weight of the polyaromatic methyl polymer is 3.2*10 4 -3.5*10 4 , the dispersity is 1.7-1.9, and the structure of the polyaromatic methyl polymer is shown in formula 2:

[0010]

[0011] In formula 2, the repeating unit comprises fluorine-substituted pendant benzyl aromatic ring structure and bisphenol A diglycidyl ether derived structure, the fluorine-substituted pendant benzyl aromatic ring structure is derived from the fluorine-substituted polyaromatic methyl monomer, and the bisphenol A diglycidyl ether derived structure is derived from bisphenol A diglycidyl ether;

[0012] The fluorine-substituted polyaromatic methyl monomer is prepared by Suzuki coupling reaction of fluorine-substituted benzyl chloride and diethyl terephthalate, and the fluorine-substituted benzyl chloride is selected from one of 4-fluorobenzyl chloride, 2,4-difluorobenzyl chloride and m-fluorobenzyl chloride;

[0013] The amount of the E-51 cross-linking agent is 0.3wt%-1.0wt% relative to the mass of the piperidyl polymer.

[0014] A preparation method of an alkali-resistant anion exchange membrane based on fluorine-substituted pendant structure polyaromatic methyl piperidine, comprising the following steps:

[0015] (1) Synthesis of fluorine-substituted polyarylmethyl monomer: 10 mmol of fluorine-substituted benzyl chloride, 5 mmol of diethyl terephthalate, and 15 mmol of potassium carbonate were added to 50 mL of N,N-dimethylformamide, and stirred at 80°C for 4 h under nitrogen protection; then 0.2 mmol of tetrakis(triphenylphosphine)palladium was added, and the Suzuki coupling reaction was carried out at 100°C for 8 h; after the reaction was completed, the mixture was cooled, filtered to remove impurities, and the solvent was removed by rotary evaporation; then the mixture was recrystallized with ethanol to obtain a white solid of fluorine-substituted polyarylmethyl monomer; the fluorine-substituted benzyl chloride is selected from one of 4-fluorobenzyl chloride, 2,4-difluorobenzyl chloride, and m-fluorobenzyl chloride;

[0016] (2) Synthesis of polyarylmethyl polymer: 8 mmol of fluorine-substituted polyarylmethyl monomer prepared in step (1), 2 mmol of bisphenol A diglycidyl ether, and 0.1 mmol of azobisisobutyronitrile were dissolved in 30 mL of dimethyl sulfoxide, and polymerized at 80°C for 6 h under nitrogen protection to obtain a yellowish viscous polyarylmethyl polymer; the number average molecular weight of the polyarylmethyl polymer is 3.2×10 4 -3.5×10 4 , the dispersity is 1.7-1.9, and the structure is shown in formula 2:

[0017] In formula 2, the repeating unit comprises a fluorine-substituted pendant benzyl aromatic ring structure derived from the fluorine-substituted polyarylmethyl monomer and a bisphenol A diglycidyl ether derived structure derived from bisphenol A diglycidyl ether;

[0018] (3) Piperidination modification: 2 g of the polyarylmethyl polymer prepared in step (2) was dissolved in 20 mL of N,N-dimethylformamide, and 4-methylpiperidine was added, the amount of 4-methylpiperidine being 1.0 eq-1.5 eq relative to the benzyl chloride groups in the polyarylmethyl polymer; after refluxing at 60°C for 4 h, dialysis treatment was performed with a dialysis molecular weight cut-off of 3500 Da and a dialysis time of 72 h to remove unreacted 4-methylpiperidine, thereby obtaining a piperidinated polymer;

[0019] (4) Crosslinking and film forming: 1 g of the piperidinated polymer prepared in step (3) was mixed with E-51 crosslinking agent, the amount of E-51 crosslinking agent being 0.3 wt%-1.0 wt% relative to the mass of the piperidinated polymer; the mixture was dissolved in 5 mL of dimethyl sulfoxide, and the mixed solution was cast into a polytetrafluoroethylene mold, dried at 60°C for 12 h, and then crosslinked at 80°C for 4 h; finally, the film was soaked in deionized water at room temperature for 24 h to obtain the alkali-resistant anion exchange membrane.

[0020] Preferably, the fluorine-substituted benzyl chloride is 2,4-difluorobenzyl chloride, and the corresponding fluorine-substituted polyarylmethyl monomer is a difluoro ortho, para-substituted pendant benzyl aromatic ring monomer.

[0021] Preferably, the amount of 4-methylpiperidine is 1.2 eq relative to the benzyl chloride groups in the polyarylmethyl polymer.

[0022] Preferably, the amount of E-51 crosslinking agent is 0.5 wt% relative to the mass of the piperidinylated polymer.

[0023] Preferably, in step (1), the fluorine-substituted benzyl chloride is 2,4-difluorobenzyl chloride, and the fluorine-substituted polyarylmethyl monomer prepared is a difluoro ortho, para-substituted pendant benzyl aromatic ring monomer.

[0024] Preferably, in step (3), the amount of 4-methylpiperidine is 1.2 eq relative to the benzyl chloride groups in the polyarylmethyl polymer.

[0025] Preferably, in step (4), the amount of E-51 crosslinking agent is 0.5 wt% relative to the mass of the piperidinylated polymer.

[0026] Preferably, in step (2), the number average molecular weight of the polyarylmethyl polymer is 3.5 x 10 4 , and the dispersity is 1.7.

[0027] Preferably, in step (1), after the solvent is removed by rotary evaporation, the yield of the fluorine-substituted polyarylmethyl monomer obtained by recrystallization with ethanol is 78%-82%.

[0028] The beneficial effects of the present application compared with the prior art are as follows:

[0029] 1. The present application designs a fluorine-substituted pendant benzyl aromatic ring structure, the strong electronegativity of the fluorine atom can enhance the polarity of the molecule, promote the formation of continuous hydrophilic microdomains in the polymer matrix, and at the same time, the pendant structure makes the cationic group away from the polymer backbone, reduces the restriction of the space steric hindrance of the main chain on ion movement, greatly improves the efficiency of hydroxyl ion conduction.

[0030] 2. The present application uses 4-methylpiperidine as a cation source, the six-membered ring structure of the piperidine ring has high steric hindrance, which can effectively inhibit the nucleophilic attack of hydroxyl group on the cation center; at the same time, the electron-withdrawing effect of the fluorine atom in the fluorine-substituted pendant structure can stabilize the positive charge of the cation, reduce the occurrence of Hofmann elimination reaction, and the pendant structure isolates the cationic group from the main chain, avoiding the influence of main chain degradation on the cationic group.

[0031] Good mechanical properties and dimensional stability: the present application forms a moderate crosslinking network in the polymer matrix by regulating the amount of E-51 crosslinking agent, which can not only inhibit the excessive swelling of the membrane in water, but also ensure the mechanical strength of the membrane; at the same time, the fluorine-substituted structure enhances the interaction between the polymer molecular chains, and improves the toughness of the membrane, such as the elongation at break of AEM-2 is 38.7%, which solves the contradiction of "high conductivity-low strength" of traditional membranes, and meets the mechanical requirements of device assembly and long-term operation.

[0032] Stable and controllable preparation process: the preparation process of the present application adopts conventional chemical synthesis method, the reaction condition is mild, and special equipment is not needed; the raw material consumption and reaction time of each step can be accurately controlled, the product has good repeatability, and is easy to scale up.

[0033] Synergistic advantage of structural design: the fluorine-substituted pendant structure and piperidinium cation form a synergistic effect-the fluorine-substituted structure optimizes the ion channel structure, improves the polarity and stability, the pendant structure guarantees the freedom of cationic group, and the piperidinium cation provides stable ion sites, the three together make the comprehensive performance of the membrane better than the prior art, and provide core material support for the performance breakthrough of alkaline energy device. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The Fourier transform infrared spectrum of AEM-2 in the present application is shown in the figure. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below, obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments.

[0036] Example 1

[0037] (1) Synthesis of fluorine-substituted polyaromatic methyl monomer

[0038] 4-fluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, potassium carbonate 15 mmol were added to DMF 50 mL, and stirred at 80℃ under N2 protection for 4h; Pd(PPh3)40.2 mmol was added, and the temperature was raised to 100℃ for Suzuki coupling reaction for 8h, after the reaction was completed, the impurities were removed by filtration, the solvent was removed by rotary evaporation, and then recrystallized with ethanol to obtain white solid monomer M1, which is a para-monofluorine-substituted pendant benzyl aromatic ring monomer, with a yield of 82%.

[0039] The structure of 4-fluorobenzyl chloride is as follows:

[0040]

[0041] (2) Synthesis of polyaromatic methyl polymer

[0042] M18 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 °C for 6 h under N2 protection to obtain a light yellow viscous polymer P1, the number average molecular weight Mn of the polymer was 3.2 x 103, and the dispersity PDI was 1.8. 4

[0043] (3) Piperidination modification

[0044] P12 g was dissolved in DMF 20 mL, and 4-methylpiperidine 1.0 eq was added, the amount being relative to the benzyl chloride groups in the polymer, and the mixture was refluxed at 60 °C for 4 h, followed by dialysis treatment with a molecular weight cut-off of 3500 Da and a dialysis time of 72 h to remove unreacted piperidine, to obtain a piperidinated polymer P1-N + .

[0045] (4) Crosslinking and film formation

[0046] P1-N + 1 g was mixed with E-51 crosslinking agent 0.5 wt%, the amount being relative to the mass of the polymer, and the mixture was dissolved in DMSO 5 mL, and the mixed solution was cast on a polytetrafluoroethylene mold, dried at 60 °C for 12 h, and then crosslinked at 80 °C for 4 h, and immersed in deionized water at room temperature for 24 h to obtain an AEM-1.

[0047] The polyarylmethyl polymer is as follows:

[0048]

[0049] Example 2

[0050] (1) Fluorine-substituted polyarylmethyl monomer synthesis

[0051] 2,4-Difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, and potassium carbonate 15 mmol were added to DMF 50 mL, and stirred at 80 °C under N2 protection for 4 h; Pd(PPh3)4 0.2 mmol was added, and the mixture was heated to 100 °C for Suzuki coupling reaction for 8 h, cooled after the reaction, filtered to remove impurities, and the solvent was removed by rotary evaporation, and then recrystallized from ethanol to obtain white solid monomer M2, which is a double-fluorine ortho-p-substituted pendant benzyl aromatic ring monomer, with a yield of 78%.

[0052] The structure of 2,4-difluorobenzyl chloride is as follows:

[0053]

[0054] (2) Polyarylmethyl polymer synthesis

[0055] ​M28 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 °C for 6 h under N2protection to obtain a light yellow viscous polymer P2, the number average molecular weight Mn of the polymer was 3.5 x 10 4 , and the dispersity PDI was 1.7.

[0056] (3) Piperidination modification

[0057] P2 2 g was dissolved in DMF 20 mL, and 4-methylpiperidine 1.0 eq was added, the amount was relative to the benzyl chloride groups in the polymer, and the mixture was refluxed at 60 °C for 4 h, followed by dialysis treatment, the dialysis molecular weight cut-off was 3500 Da, and the dialysis time was 72 h to remove the unreacted piperidine, to obtain a piperidinated polymer P2-N + .

[0058] (4) Crosslinking film formation

[0059] P2-N + 1 g was mixed with E-51 crosslinking agent 0.5 wt%, the amount was relative to the polymer mass, and the mixture was dissolved in DMSO 5 mL, and the mixed solution was cast on a polytetrafluoroethylene mold, dried at 60 °C for 12 h, and then crosslinked at 80 °C for 4 h, and soaked in deionized water at room temperature for 24 h to obtain AEM-2.

[0060] Example 3

[0061] (1) Fluorine-substituted polyarylmethyl monomer synthesis

[0062] M-fluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, and potassium carbonate 15 mmol were added to DMF 50 mL, and stirred at 80 °C for 4 h under N2protection; Pd(PPh3)4 0.2 mmol was added, and the temperature was increased to 100 °C for Suzuki coupling reaction for 8 h, and after the reaction was completed, the temperature was cooled, impurities were removed by filtration, the solvent was removed by rotary evaporation, and then recrystallized from ethanol to obtain white solid monomer M3, the monomer was a meta-monofluorine-substituted pendant benzyl aromatic ring monomer, and the yield was 80%.

[0063] The structure of m-fluorobenzyl chloride is as follows:

[0064]

[0065] (2) Polyarylmethyl polymer synthesis

[0066] M3 8 mmol, BADGE 2 mmol, and AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 °C for 6 h under N2protection to obtain a light yellow viscous polymer P3, the number average molecular weight Mn of the polymer was 3.2 x 10 4 , and the dispersity PDI was 1.9.

[0067] (3) Piperidination modification

[0068] P32g was dissolved in DMF 20 mL, 4-methylpiperidine 1.0 eq was added, the amount was relative to the benzyl chloride groups in the polymer, and the reaction was carried out at 60°C for 4 h, followed by dialysis treatment, the dialysis molecular weight cut-off was 3500 Da, and the dialysis time was 72 h to remove the unreacted piperidine, to obtain the piperidinated polymer P3-N. + .

[0069] (4) Crosslinking film formation

[0070] P3-N + 1g was mixed with E-51 crosslinking agent 0.5 wt%, the amount was relative to the mass of the polymer, and the mixture was dissolved in DMSO 5 mL, the mixed solution was cast on a polytetrafluoroethylene mold, dried at 60°C for 12 h, then crosslinked at 80°C for 4 h, and soaked in deionized water at room temperature for 24 h, to obtain AEM-3.

[0071] Example 4:

[0072] (1) Fluorine-substituted polyarylmethyl monomer synthesis

[0073] 2,4-difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, potassium carbonate 15 mmol were added to DMF 50 mL, stirred at 80°C under N2 protection for 4 h; Pd(PPh3)4 was added, and the temperature was raised to 100°C for Suzuki coupling reaction for 8 h, after the reaction was completed, the temperature was cooled, the impurities were removed by filtration, the solvent was removed by rotary evaporation, and then recrystallized from ethanol to obtain white solid monomer M2, which was a double fluorine ortho-p-substituted pendant benzyl aromatic ring monomer, with a yield of 78%.

[0074] (2) Polyarylmethyl polymer synthesis

[0075] M2 28 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80°C under N2 protection for 6 h to obtain a light yellow viscous polymer P2, which had a number average molecular weight Mn of 3.2 x 10 4 , and a dispersity PDI of 1.7.

[0076] (3) Piperidination modification

[0077] P22g was dissolved in DMF 20 mL, 4-methylpiperidine 1.0 eq was added, the amount was relative to the benzyl chloride groups in the polymer, and the reaction was carried out at 60°C for 4 h, followed by dialysis treatment, the dialysis molecular weight cut-off was 3500 Da, and the dialysis time was 72 h to remove the unreacted piperidine, to obtain the piperidinated polymer P4-N. + .

[0078] (4) Crosslinking and film formation

[0079] P4-N + was mixed with E-51 crosslinking agent 0.5 wt%, the amount relative to the mass of the polymer, and dissolved in DMSO 5 mL together, and the mixed solution was cast on a polytetrafluoroethylene mold, dried at 60°C for 12 h, then crosslinked at 80°C for 4 h, soaked in deionized water at room temperature for 24 h to obtain AEM-4.

[0080] Example 5:

[0081] (1) Fluorine-substituted polyarylmethyl monomer synthesis

[0082] 2,4-difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, potassium carbonate 15 mmol were added to DMF 50 mL, stirred at 80°C under N2 protection for 4 h; Pd(PPh3)4 0.2 mmol was added, and the temperature was raised to 100°C for Suzuki coupling reaction for 8 h. After the reaction was completed, the impurities were removed by filtration, and the solvent was removed by rotary evaporation, and then recrystallized with ethanol to obtain white solid monomer M2. This monomer is a double fluorine ortho-p-substituted pendant benzyl aromatic ring monomer, with a yield of 78%.

[0083] (2) Synthesis of polyarylmethyl polymer

[0084] M2 28 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80°C under N2 protection for 6 h to obtain a light yellow viscous polymer P2. The number average molecular weight Mn of this polymer was 3.5 x 10 4 , and the dispersity PDI was 1.7.

[0085] (3) Piperidination modification

[0086] P2 2 g was dissolved in DMF 20 mL, and 4-methylpiperidine 1.2 eq was added, the amount relative to the benzyl chloride group in the polymer, and refluxed at 60°C for 4 h, followed by dialysis treatment with a molecular weight cut-off of 3500 Da, and dialysis for 72 h to remove unreacted piperidine to obtain piperidinated polymer P5-N + .

[0087] (4) Crosslinking and film formation

[0088] P5-N + was mixed with E-51 crosslinking agent 0.5 wt%, the amount relative to the mass of the polymer, and dissolved in DMSO 5 mL together, and the mixed solution was cast on a polytetrafluoroethylene mold, dried at 60°C for 12 h, then crosslinked at 80°C for 4 h, soaked in deionized water at room temperature for 24 h to obtain AEM-5.

[0089] Example 6

[0090] (1) Fluorine-substituted polyarylmethyl monomer synthesis

[0091] 2,4-difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, potassium carbonate 15 mmol were added to DMF 50 mL, stirred at 80 °C under N2protection for 4 h; Pd(PPh3)40.2 mmol was added, and the temperature was raised to 100 °C for Suzuki coupling reaction for 8 h. After the reaction was completed, the mixture was cooled, filtered to remove impurities, and the solvent was removed by rotary evaporation. The white solid monomer M2 was obtained by recrystallization from ethanol. The monomer was a double fluorine ortho-p-substituted pendant benzyl aromatic ring monomer with a yield of 78%.

[0092] (2) Polyarylmethyl polymer synthesis

[0093] M2 28 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerization was carried out at 80 °C under N2protection for 6 h to obtain a light yellow viscous polymer P2. The number average molecular weight Mn of the polymer was 3.5 x 10 4 , and the dispersity PDI was 1.7.

[0094] (3) Piperidination modification

[0095] P2 2 g was dissolved in DMF 20 mL, and 4-methylpiperidine 1.5 eq was added. The amount was relative to the benzyl chloride group in the polymer. The reaction was carried out at 60 °C for 4 h, followed by dialysis treatment with a molecular weight cut-off of 3500 Da for 72 h to remove unreacted piperidine, to obtain the piperidinated polymer P6-N + .

[0096] (4) Crosslinking film formation

[0097] P6-N + 1 g was mixed with E-51 crosslinking agent 0.5 wt%, the amount was relative to the polymer mass, and the mixture was dissolved in DMSO 5 mL. The mixed solution was cast on a polytetrafluoroethylene mold, dried at 60 °C for 12 h, then crosslinked at 80 °C for 4 h, and soaked in deionized water at room temperature for 24 h to obtain AEM-6.

[0098] Example 7:

[0099] (1) Fluorine-substituted polyarylmethyl monomer synthesis

[0100] The 2,4-difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, potassium carbonate 15 mmol were added to DMF 50 mL, stirred at 80 ℃ under N2 protection for 4 h; Pd(PPh3)4 0.2 mmol was added, and the temperature was raised to 100 ℃ for Suzuki coupling reaction for 8 h. After the reaction was completed, it was cooled, filtered to remove impurities, rotary evaporation to remove the solvent, and then recrystallized from ethanol to obtain white solid monomer M2. The monomer is a double-fluorine ortho-p-substituted pendant benzyl aromatic ring monomer, and the yield is 78%.

[0101] (2) Synthesis of polyarylmethyl polymer

[0102] M2 28 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 ℃ under N2 protection for 6 h to obtain a light yellow viscous polymer P2. The number average molecular weight Mn of the polymer is 3.5×10 4 , and the dispersity PDI is 1.7.

[0103] (3) Piperidination modification

[0104] P2 2 g was dissolved in DMF 20 mL, and 4-methylpiperidine 1.2 eq was added. The amount is relative to the benzyl chloride group in the polymer. The reaction was carried out at 60 ℃ for 4 h, followed by dialysis treatment. The dialysis molecular weight cut-off is 3500 Da, and the dialysis time is 72 h to remove unreacted piperidine. Piperidinated polymer P7-N + was obtained.

[0105] (4) Crosslinking film formation

[0106] P7-N + 1 g was mixed with E-51 crosslinking agent 0.3 wt%. The amount is relative to the mass of the polymer. The mixture was dissolved in DMSO 5 mL, and the mixed solution was cast on a polytetrafluoroethylene mold. The mold was dried at 60 ℃ for 12 h, and then crosslinked at 80 ℃ for 4 h. The film was soaked in deionized water at room temperature for 24 h to obtain AEM-7.

[0107] Example 8:

[0108] (1) Synthesis of fluorine-substituted polyarylmethyl monomer

[0109] The 2,4-difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, potassium carbonate 15 mmol were added to DMF 50 mL, stirred at 80 ℃ under N2 protection for 4 h; Pd(PPh3)4 0.2 mmol was added, and the temperature was raised to 100 ℃ for Suzuki coupling reaction for 8 h. After the reaction was completed, it was cooled, filtered to remove impurities, rotary evaporation to remove the solvent, and then recrystallized from ethanol to obtain white solid monomer M2. The monomer is a double-fluorine ortho-p-substituted pendant benzyl aromatic ring monomer, and the yield is 78%.

[0110] (2) Polyarylmethyl polymer synthesis

[0111] M2 8 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 °C for 6 h under N2protection to obtain a yellowish viscous polymer P2, which had a number average molecular weight Mn of 3.5 x 104and a dispersity PDI of 1.7. 4

[0112] (3) Piperidination modification

[0113] P2 2 g was dissolved in DMF 20 mL, and 4-methylpiperidine 1.2 eq was added, which was based on the benzyl chloride groups in the polymer, and the mixture was refluxed at 60 °C for 4 h, followed by dialysis treatment with a molecular weight cut-off of 3500 Da for 72 h to remove unreacted piperidine to obtain a piperidinated polymer P8-N + .

[0114] (4) Crosslinking film formation

[0115] P8-N + 1 g was mixed with E-51 crosslinking agent 0.5 wt%, which was based on the polymer mass, and the mixture was dissolved in DMSO 5 mL, and the mixed solution was cast on a polytetrafluoroethylene mold, which was dried at 60 °C for 12 h, and then crosslinked at 80 °C for 4 h, and soaked in deionized water at room temperature for 24 h to obtain an AEM-8.

[0116] Example 9:

[0117] (1) Fluorine-substituted polyarylmethyl monomer synthesis

[0118] 2,4-difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, and potassium carbonate 15 mmol were added to DMF 50 mL, and stirred at 80 °C for 4 h under N2protection; Pd(PPh3)4 0.2 mmol was added, and the mixture was heated to 100 °C for Suzuki coupling reaction for 8 h, and then cooled, filtered to remove impurities, and the solvent was removed by rotary evaporation, followed by recrystallization from ethanol to obtain white solid monomer M2, which was a double-fluorine ortho, para-substituted pendant benzyl aromatic ring monomer, with a yield of 78%.

[0119] (2) Polyarylmethyl polymer synthesis

[0120] M2 8 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 °C for 6 h under N2protection to obtain a yellowish viscous polymer P2, which had a number average molecular weight Mn of 3.5 x 104and a dispersity PDI of 1.7. 4

[0121] ​​(3) Piperidinylation modification

[0122] P2 2 g was dissolved in DMF 20 mL, 4-methylpiperidine 1.2 eq was added, the amount was relative to the benzyl chloride group in the polymer, and the reaction was carried out at 60°C for 4 h, followed by dialysis treatment, the dialysis molecular weight cut-off was 3500 Da, and the dialysis time was 72 h to remove unreacted piperidine, to obtain piperidinylation polymer P9-N. + .

[0123] (4) Crosslinking film formation

[0124] P9-N + 1 g was mixed with E-51 crosslinking agent 0.8 wt%, the amount was relative to the mass of the polymer, and the mixture was dissolved in DMSO 5 mL, the mixed solution was cast on a polytetrafluoroethylene mold, dried at 60°C for 12 h, then crosslinked at 80°C for 4 h, and soaked in deionized water at room temperature for 24 h, to obtain AEM-9.

[0125] The structural formula of diethyl terephthalate is as follows:

[0126]

[0127]

[0128] The Fourier transform infrared spectroscopy (FT-IR) test was performed on AEM-2 prepared in Example 2 of the present application to verify the key reaction process and structural stability, and the results are shown in Figure 1 .

[0129] As can be seen from Figure 1 , it is proved that the piperidinylation modification is complete, the crosslinking reaction is sufficient, and the membrane structure has excellent stability under adsorption simulation conditions.

[0130] Comparative Example 1

[0131] (1) Synthesis of polyaromatic methyl monomer

[0132] Benzyl chloride 10 mmol, diethyl terephthalate 5 mmol, potassium carbonate 15 mmol were added to DMF 50 mL, stirred at 80°C under N2 protection for 4 h; Pd(PPh3)4 0.2 mmol was added, and the Suzuki coupling reaction was carried out at 100°C for 8 h, after the reaction was completed, the impurities were removed by filtration, the solvent was removed by rotary evaporation, and then recrystallized from ethanol to obtain white solid monomer MC1, the monomer is a fluorine-free substituted pendant benzyl aromatic ring monomer, the yield is 81%.

[0133] (2) Synthesis of polyaromatic methyl polymer

[0134] MC 18 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 °C for 6 h under N2protection to obtain a yellowish viscous polymer PCl, which had a number average molecular weight Mn of 3.4 x 10 4 and a polydispersity PDI of 1.8.

[0135] (3) Piperidination modification

[0136] PCl 2 g was dissolved in DMF 20 mL, and 4-methylpiperidine 1.0 eq was added, which was based on the benzyl chloride groups in the polymer, and the mixture was refluxed at 60 °C for 4 h, followed by dialysis treatment with a molecular weight cut-off of 3500 Da for 72 h to remove unreacted piperidine to obtain a piperidinated polymer PCl-N + .

[0137] (4) Crosslinking and film formation

[0138] PCl-N + 1 g was mixed with E-51 crosslinking agent 0.5 wt%, which was based on the mass of the polymer, and the mixture was dissolved in DMSO 5 mL, and the solution was cast on a polytetrafluoroethylene mold, which was dried at 60 °C for 12 h, and then crosslinked at 80 °C for 4 h, and soaked in deionized water at room temperature for 24 h to obtain an AEM-C1.

[0139] Comparative Example 2

[0140] (1) Fluorine-substituted polyarylmethyl monomer synthesis

[0141] 2,4-difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, and potassium carbonate 15 mmol were added to DMF 50 mL, and stirred at 80 °C for 4 h under N2protection; Pd(PPh3)4 0.2 mmol was added, and the mixture was heated to 100 °C for Suzuki coupling reaction for 8 h, and then cooled, filtered to remove impurities, and the solvent was removed by rotary evaporation, and then recrystallized from ethanol to obtain a white solid monomer M2, which was a double-fluorine ortho, para-substituted pendant benzyl aromatic ring monomer, with a yield of 78%.

[0142] (2) Polyarylmethyl polymer synthesis

[0143] M2 8 mmol, BADGE 2 mmol, and AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 °C for 6 h under N2protection to obtain a yellowish viscous polymer P2, which had a number average molecular weight Mn of 3.5 x 10 4 and a polydispersity PDI of 1.7.

[0144] (3) Quaternary ammonium modification

[0145] P2 2 g was dissolved in DMF 20 mL, trimethylamine 1.0 eq was added, the amount was relative to the benzyl chloride groups in the polymer, and the reaction was carried out at 60 °C for 4 h, followed by dialysis treatment, the dialysis molecular weight cut-off was 3500 Da, and the dialysis time was 72 h to remove the unreacted trimethylamine, to obtain the quaternary ammonium polymer PC2-N + .

[0146] (4) Crosslinking and film formation

[0147] PC2-N + 1 g was mixed with E-51 crosslinking agent 0.5 wt%, the amount was relative to the polymer mass, and the mixture was dissolved in DMSO 5 mL, the mixed solution was cast on a polytetrafluoroethylene mold, dried at 60 °C for 12 h, then crosslinked at 80 °C for 4 h, and soaked in deionized water at room temperature for 24 h, to obtain AEM-C2.

[0148] Comparative Example 3: Preparation of a fluorine-substituted piperidine AEM without a pendant structure

[0149] (1) Synthesis of a fluorine-containing polymer without a pendant structure

[0150] The main chain fluorine-containing polyarylether ketone 2 g was dissolved in DMF 20 mL, and stirred at 80 °C for 2 h under N2 protection, to obtain a uniform polymer solution.

[0151] (2) Piperidination modification

[0152] Trimethylamine 1.0 eq was added to the above polymer solution, the amount was relative to the reactive groups in the polymer, and the reaction was carried out at 60 °C for 4 h, followed by dialysis treatment, the dialysis molecular weight cut-off was 3500 Da, and the dialysis time was 72 h to remove the unreacted trimethylamine, to obtain the piperidinated polymer PC3-N + .

[0153] (3) Crosslinking and film formation

[0154] PC3-N + 1 g was mixed with E-51 crosslinking agent 0.5 wt%, the amount was relative to the polymer mass, and the mixture was dissolved in DMSO 5 mL, the mixed solution was cast on a polytetrafluoroethylene mold, dried at 60 °C for 12 h, then crosslinked at 80 °C for 4 h, and soaked in deionized water at room temperature for 24 h, to obtain AEM-C3.

[0155] Comparative Example 4:

[0156] (1) Synthesis of a fluorine-substituted polyaromatic methyl monomer

[0157] 2,4-difluorobenzyl chloride 10 mmol, diethyl terephthalate 5 mmol, potassium carbonate 15 mmol were added into DMF 50 mL, and stirred at 80 °C for 4 h under N2 protection. Pd(PPh3)4 0.2 mmol was added, and the Suzuki coupling reaction was carried out at 100 °C for 8 h. After the reaction was completed, the mixture was cooled, filtered to remove impurities, and the solvent was removed by rotary evaporation. The white solid monomer M2 was obtained by recrystallization from ethanol. The monomer was a double-fluoro ortho-p-substituted pendant benzyl aromatic ring monomer, and the yield was 78%.

[0158] (2) Synthesis of polyarylmethyl polymer

[0159] M2 28 mmol, BADGE 2 mmol, AIBN 0.1 mmol were dissolved in DMSO 30 mL, and polymerized at 80 °C for 6 h under N2 protection to obtain a light yellow viscous polymer P2. The number average molecular weight Mn of the polymer was 3.5 × 10 4 , and the dispersity PDI was 1.7.

[0160] (3) Piperidination modification

[0161] P2 2 g was dissolved in DMF 20 mL, and 4-methylpiperidine 1.0 eq was added. The amount was relative to the benzyl chloride group in the polymer. The reaction was carried out at 60 °C for 4 h, followed by dialysis treatment with a molecular weight cut-off of 3500 Da for 72 h to remove unreacted piperidine, to obtain the piperidinated polymer PC4-N + .

[0162] (4) Crosslinking and film formation

[0163] PC4-N + 1 g was mixed with E-51 crosslinking agent 1.0 wt%, and the amount was relative to the mass of the polymer. The mixture was dissolved in DMSO 5 mL, and the mixed solution was cast on a polytetrafluoroethylene mold. The mold was dried at 60 °C for 12 h, and then crosslinked at 80 °C for 4 h. The film was soaked in deionized water at room temperature for 24 h to obtain AEM-C4.

[0164] Performance test methods and results

[0165] (1) Key test methods

[0166] IEC test: The potential titration method was used. The membrane was soaked in 0.1 M HCl solution for 24 h, and then titrated with 0.1 M NaOH to determine the ion exchange capacity, with the unit of mmol / g.

[0167] Hydroxyl ion conductivity (σ) test: The four-probe method was used, and the test temperature was 25 °C and 60 °C, respectively. The membrane was soaked in deionized water for 24 h before the test, and then the surface water was wiped off for the test. The conductivity unit was mS / cm.

[0168] Alkali stability test: The membrane was immersed in 6M KOH solution, the solution temperature was controlled at 80℃, the hydroxyl ion conductivity retention rate and IEC retention rate of the membrane after immersion for 100h, 500h, 1000h were tested respectively, the retention rate was expressed in percentage.

[0169] Mechanical property test: The tensile strength (TS) and elongation at break (EB) of the dry membrane were tested at room temperature, the unit of tensile strength was MPa, and the elongation at break was expressed in percentage.

[0170] Water uptake (WR) and swelling degree (SR) test: The membrane was immersed in deionized water at 60℃ for 24h, the water uptake was calculated according to the formula WR = (Wwet-Wdry) / Wdryx100%, and the swelling degree was calculated according to the formula SR = (Lwet-Ldry) / Ldryx100%, the results were expressed in percentage.

[0171] Table 1 Performance test results table:

[0172]

[0173]

[0174]

[0175] The results are analyzed as follows:

[0176] Fluorine substitution correlation: AEM-2 is a double fluorine ortho-substitution structure, compared with the single fluorine para-substitution structure of AEM-1 and the single fluorine meta-substitution structure of AEM-3, its hydroxyl ion conductivity is increased by 15%-23%, and the alkali resistance retention rate is increased by 8%-12%. This result shows that double fluorine substitution can enhance the molecular polarity and steric hindrance, thereby significantly improving the ion conduction performance and alkali resistance stability.

[0177] Piperidine degree correlation: In AEM-4 to AEM-6, the amount of 4-methyl piperidine is increased from 1.0 eq to 1.5 eq, and the IEC is increased from 1.32 mmol / g to 1.82 mmol / g, and the hydroxyl ion conductivity is also increased synchronously, but the 1000h alkali conductivity retention rate is decreased from 85.3% to 70.2%. The reason is that excessive cationic groups are easily attacked by OH-, which proves that 1.2 eq is the optimal piperidine degree.

[0178] Crosslinker dosage correlation: In AEM-7 to AEM-9, the amount of E-51 crosslinker is increased from 0.3wt% to 0.8wt%, the tensile strength is increased from 25.8MPa to 38.2MPa, but the hydroxyl ion conductivity is decreased by 10%, and the elongation at break is decreased from 42.3% to 22.6%. This change shows that the amount of 0.5wt% crosslinker can balance the mechanical properties and ion conduction properties.

[0179] The comparative advantage: AEM-2 is 35% higher than AEM-C1 in terms of fluoride-free substitution alkali resistance retention, 55% higher than AEM-C2 in terms of quaternary ammonium salt type alkali resistance retention, and 43% higher than AEM-C3 in terms of hydroxyl ion conductivity without pendant structure. The above data prove that the synergistic effect of fluoride substitution pendant structure and piperidine cation is the core factor to improve the alkali resistance and high conductivity of the membrane.

[0180] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details and limit the present application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the present application. The present application is selected and specifically described in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application. The present application is only subject to the claims and the entire scope and equivalents.

Claims

1. An alkali-resistant anion exchange membrane based on fluorine-substituted pendant structure polyarylmethylpiperidines, characterized by, The anion exchange membrane is prepared by cross-linking reaction of piperidyl polymer and E-51 cross-linking agent; The piperidyl polymer is obtained by modifying polyarylmethyl polymer with 4-methylpiperidine, and the amount of 4-methylpiperidine is 1.0 eq-1.5 eq relative to benzyl chloride groups in the polyarylmethyl polymer; The polyarylmethyl polymer is formed by polymerization of a fluorine-substituted polyarylmethyl monomer and bisphenol A diglycidyl ether in the presence of azobisisobutyronitrile, the molar ratio of the fluorine-substituted polyarylmethyl monomer to bisphenol A diglycidyl ether is 8:2, the amount of azobisisobutyronitrile is 0.1 mmol and corresponds to the total amount of 8 mmol of fluorine-substituted polyarylmethyl monomer and 2 mmol of bisphenol A diglycidyl ether, the number average molecular weight of the polyarylmethyl polymer is 3.2 x 10 4 -3.5 x 10 4 , the dispersity is 1.7-1.9, and the structure of the polyarylmethyl polymer is shown in Formula 2: In formula 2, the repeating unit comprises a fluorine-substituted pendant benzyl aromatic ring structure derived from the fluorine-substituted polyarylmethyl monomer and a bisphenol A diglycidyl ether derived structure derived from bisphenol A diglycidyl ether; The fluorine-substituted polyarylmethyl monomer is prepared by Suzuki coupling reaction of fluorine-substituted benzyl chloride and diethyl terephthalate, and the fluorine-substituted benzyl chloride is selected from one of 4-fluorobenzyl chloride, 2,4-difluorobenzyl chloride, and m-fluorobenzyl chloride; The amount of E-51 cross-linking agent is 0.3wt%-1.0wt% relative to the mass of piperidyl polymer.

2. A process for producing the alkali-resistant anion exchange membrane based on fluorine-substituted pendant structure polyarylmethylpiperidine according to claim 1, characterized by, It comprises the following steps: (1) Fluorine-substituted polyarylmethyl monomer synthesis: 10 mmol of fluorine-substituted benzyl chloride, 5 mmol of diethyl terephthalate, and 15 mmol of potassium carbonate are added to 50 mL of N,N-dimethylformamide, and stirred at 80°C under nitrogen protection for 4 hours; then 0.2 mmol of tetrakis triphenylphosphine palladium is added, and the temperature is raised to 100°C for Suzuki coupling reaction for 8 hours; after the reaction is completed, it is cooled, filtered to remove impurities, rotary evaporation to remove the solvent, and then recrystallized with ethanol to obtain a white solid of fluorine-substituted polyarylmethyl monomer; the fluorine-substituted benzyl chloride is selected from one of 4-fluorobenzyl chloride, 2,4-difluorobenzyl chloride, and m-fluorobenzyl chloride; (2) Synthesis of polyarylmethyl polymer: 8 mmol of fluorine-substituted polyarylmethyl monomer prepared in step (1), 2 mmol of bisphenol A diglycidyl ether, and 0.1 mmol of azobisisobutyronitrile were dissolved in 30 mL of dimethyl sulfoxide, and polymerization was performed at 80°C for 6 h under nitrogen protection to obtain a yellowish viscous polyarylmethyl polymer; the number average molecular weight of the polyarylmethyl polymer was 3.2 x 10 4 -3.5 x 10 4 , the dispersity was 1.7-1.9, and the structure was shown in formula 2: In formula 2, the repeating unit comprises a fluorine-substituted pendant benzyl aromatic ring structure derived from the fluorine-substituted polyarylmethyl monomer and a bisphenol A diglycidyl ether derived structure derived from bisphenol A diglycidyl ether; (3) Piperidyl modification: 2 g of polyarylmethyl polymer prepared in step (2) is dissolved in 20 mL of N,N-dimethylformamide, and 4-methylpiperidine is added, and the amount of 4-methylpiperidine is 1.0 eq-1.5 eq relative to benzyl chloride groups in the polyarylmethyl polymer; after refluxing at 60°C for 4 hours, dialysis treatment is performed with a dialysis molecular weight cut-off of 3500 Da and a dialysis time of 72 hours to remove unreacted 4-methylpiperidine, and a piperidyl polymer is obtained; (4) Cross-linking film formation: 1 g of piperidyl polymer prepared in step (3) is mixed with E-51 cross-linking agent, and the amount of E-51 cross-linking agent is 0.3wt%-1.0wt% relative to the mass of piperidyl polymer; the mixture is dissolved in 5 mL of dimethyl sulfoxide, and the mixed solution is cast in a polytetrafluoroethylene mold, dried at 60°C for 12 hours, and then cross-linked at 80°C for 4 hours; finally, the membrane is soaked in deionized water at room temperature for 24 hours to obtain the alkali-resistant anion exchange membrane.

3. The alkali-resistant anion exchange membrane according to claim 1, characterized in that, The fluorine-substituted benzyl chloride is 2,4-difluorobenzyl chloride, and the corresponding fluorine-substituted polyarylmethyl monomer is a double-fluorine ortho-p-substituted pendant benzyl aromatic ring monomer.

4. The alkali-resistant anion exchange membrane according to claim 1, characterized in that, The amount of 4-methylpiperidine used is 1.2 eq relative to the benzyl chloride groups in the polyarylmethyl polymer.

5. The alkali-resistant anion exchange membrane according to claim 1, wherein The amount of E-51 crosslinking agent used is 0.5 wt% relative to the mass of the piperidinized polymer.

6. The preparation method according to claim 2, characterized in that, In step (1), the fluorine-substituted benzyl chloride is 2,4-difluorobenzyl chloride, and the fluorine-substituted polyarylmethyl monomer prepared is a difluoro ortho-para-substituted pendant benzyl aromatic ring monomer.

7. The preparation method according to claim 2, characterized in that, In step (3), the amount of 4-methylpiperidine used is 1.2 eq relative to the benzyl chloride groups in the polyarylmethyl polymer.

8. The preparation method according to claim 2, characterized in that, In step (4), the amount of E-51 crosslinking agent used is 0.5 wt% relative to the mass of the piperidinized polymer.

9. The method of claim 2, wherein, In step (2), the number average molecular weight of the polyarylmethyl polymer is 3.5 x 10 4 , and the dispersity is 1.

7.

10. The method of claim 2, wherein, In step (1), after the solvent is removed by rotary evaporation, the fluorine-substituted polyarylmethyl monomer obtained by recrystallization from ethanol has a yield of 78%-82%.

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