Polymer, modified anion exchange membrane and preparation method and application thereof

Abstract

The invention relates to the technical field of new materials, in particular to a polymer, an ion exchange membrane and a preparation method and application thereof. The polymer is a compound shown in a general formula I, r is; n is the content of non-quaternized piperidine in the main chain, and n is equal to 0-1; z = n / 2. The end-capping reagent is introduced by adopting a gas-solid reaction method, that is, the membrane reacts with the vaporized end-capping reagent. The method has a positioning effect on a polymer molecular chain, so that a static polymer chain and a dynamic end-capping reagent are in a positioning and fixed-point reaction when the end-capping reaction occurs, and self-crosslinking caused by high movement of the polymer chain is prevented. In addition, the space structure of a triazine network cross-linking site is regulated and controlled by optimizing an end-capping reagent, and the purpose of improving the stability and OH <-> conductivity of the thin film at the same time is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a polymer, a modified anion exchange membrane, and a preparation method and application thereof. Background Art

[0002] Hydrogen not only has low volume density, high energy content and significant flammability, but also produces only water and heat as by-products, making it an ideal energy carrier and green fuel. Green hydrogen mainly comes from water electrolysis. At present, water electrolysis technology is mainly divided into solid oxide electrolyzers, proton exchange membrane water electrolysis, alkaline water electrolysis and hydroxide ion exchange membrane water electrolysis (HEMWE). Among them, low-temperature HEMWE is an effective green energy conversion technology route. HEMWE is mainly composed of hydroxide ion exchange membrane (HEM) and catalyst. HEM can conduct OH- and isolate the generated H2 and O2, which directly determines the performance and durability of the water electrolyzer. Therefore, the development of high-performance, low-cost HEM is crucial to promote efficient water electrolysis and large-scale application.

[0003] HEMs primarily consist of a polymer backbone and cationic groups. Polymer backbones can generally be categorized into linear and network types. Network polymer backbones are preferred due to their structural stability. Using aliphatic crosslinkers to crosslink linear polymers allows for the easy creation of high-performance, flexible network HEMs. Meanwhile, in recent years, researchers have focused their attention on rigid aromatic ring-crosslinked polyarylpiperidines. For example, in 2022, Hu Xile et al. developed a branched polybiphenylpiperidinium HEM (b-PTP) using triphenylbenzene as the basic crosslinking backbone. The OH- conductivity exceeded 145 mS cm⁻¹ at 80°C, and the water absorption expansion rate was less than 30%. b-PTP also exhibited an alkaline stability of 1500 h at 80°C in 1 M KOH. In the same year, Qing Lin Liu et al. prepared a branched polyarylpiperidinium HEM (PTTPQ4-40) using triphenylmethane as the basic cross-linking backbone. The OH- conductivity was 155.3 mS cm⁻¹ at 80°C and the alkaline stability was 1080 hours in 2 M NaOH. Compared with linear HEMs (up to 208 mS cm⁻¹) and flexible network HEMs (up to 196.3 mS cm⁻¹), rigid network HEMs exhibited higher dimensional stability but relatively lower OH- conductivity. This is primarily due to the dense covalent bonds that create a rigid network with a high energy barrier, which inhibits OH- migration.

[0004] In the past, to address the challenge of low conductivity, cationic end-groups were often embedded into linear polymer chains to enhance OH- conductivity. For example, in 2013, Junpei Miyake et al. prepared fluorinated polyphenylene ether ion exchange membranes with five quaternary amine end-groups. These end-groups were trimethylamine, n-butyldimethylamine, 1-methylimidazole, 1,2-dimethylimidazole (DMIm), and pyridine (PYR). Notably, while the ion exchange capacities of the ionomers capped with DMIm and PYR differed by a factor of 13, this suggests that the end-group plays a crucial role in the ionic conductivity of the ionomer membranes. In the same year, Xiuhua Li et al. systematically investigated the effects of end-groups such as imidazole (MIm), pyridine, trimethylamine (TMA), and triethylamine on poly(aryl ether sulfone) ionomer membranes. Their data also showed that while the ion exchange capacity of polybenzylbenzene with TMA end-capping groups was higher than that with MIM end-capping groups, the ion conductivity showed the opposite effect. In 2016, Zhuang Lin et al. prepared polybenzylbenzene ionomers with different end-capping groups, including trimethylamine (TMA), n-methylpyrrolidine (MPY), and n-methylpiperidine. Their data also revealed an interesting phenomenon: a negative correlation between ion conductivity and ion exchange capacity. For example, the ion exchange capacity of the ionomer with MPY end-capping groups was 9% lower than that of the ionomer with TMA end-capping groups, while its conductivity was 20.5% higher. This phenomenon leads to the conclusion that, in addition to ion exchange capacity, molecular configuration is another important factor influencing ion conductivity. By manipulating the appropriate end-capping groups, it is possible to construct a suitable spatial configuration and create cavity channels suitable for ion transport.

[0005] Therefore, it is reasonable to use cationic end-capping groups to embed the cross-linking sites of network polymers to improve OH- conductivity and stability. Obviously, to achieve the above goals, the development of end-capping methods based on the synthetic characteristics of network polymers is particularly important, which is conducive to high stability and high OH - The synthesis and preparation of conductive rigid network HEM ​​is of great significance and is an important part of the development of efficient water electrolysis technology for green hydrogen production. Summary of the Invention

[0006] The present invention provides a polymer having a compound represented by the general formula I: ; R is ; n is the unquaternized piperidine content in the main chain, n=0~1; z=n / 2.

[0007] According to the polymer provided by the present invention, n is 0, 0.2, 0.4, 0.6 or 0.8; z is 0, 0.1, 0.2, 0.3 or 0.4; nz=n / 2, which is 0, 0.1, 0.2, 0.3 or 0.4.

[0008] In a second aspect, the present invention provides a method for preparing the polymer, comprising: (1) Biphenyl and N-methyl-4-piperidone are polymerized by superacid catalysis to obtain polybiphenylpiperidine; (2) reacting the polybiphenyl piperidine with iodomethane to prepare a partially quaternized polybiphenyl piperidinium; (3) cross-linking the partially quaternized polybiphenylpiperidinium with cyanuric chloride to obtain a cross-linked polymer film; (4) Immersing the cross-linked polymer film in a vaporized atmosphere of a pure capping agent to perform a capping reaction; the capping agent is N-methylpyrrolidine.

[0009] In the present invention, the membrane is immersed in a pure capping agent vaporized atmosphere to carry out the capping reaction, wherein the capping agent is vaporized steam.

[0010] The cross-linking sites of the triazine network containing piperidine groups contain residual chlorinated groups that can react with the capping agent to perform ion capping, thereby increasing the ion exchange capacity of the film. However, the capping agent is a base, which is also conducive to promoting the reaction of chlorine in the network with piperidine to continue self-crosslinking. Based on this phenomenon, the present invention introduces the capping agent by adopting a gas-solid reaction method, that is, reacting with the vaporized capping agent through the membrane. This method has a positioning effect on the polymer molecular chain, so that when the capping reaction occurs, the static polymer chain and the dynamic capping agent are in a positioned and fixed-point reaction to prevent the polymer chain from highly moving and self-crosslinking. The present invention solves the problem of excessive cross-linking of polymer molecules caused by cross-linking to produce a large number of dense covalent bond networks, thereby causing a decrease in ion conductivity, by adopting different methods of introducing capping agents, and further achieves the simultaneous improvement of the stability of the film and OH. - Conductivity.

[0011] Under the premise of applying the gas-solid reaction method, different end-capping groups construct different cavities at the cross-linking sites. The present invention surprisingly discovered that N-methylpyrrolidine-terminated triazine cross-linked polybiphenylpiperidinium can construct a more regular and orderly cavity structure, solving the problem of molecular chain cross-linking causing the internal cavity to become smaller, thereby causing a decrease in ion conductivity, and further achieving the simultaneous improvement of the stability and OH- conductivity of the film.

[0012] At the same time, the membrane material of the present invention has high stability: rigid triazine cross-linked polyaryl piperidine is used to prepare chemically cross-linked polyaryl piperidinium, which is beneficial to improving the energy barrier of molecular chain movement, can effectively reduce the swelling phenomenon in the interstitial channels, and significantly improve the operating stability and service life of the hydroxide ion exchange membrane.

[0013] According to the method for preparing the polymer, step (4) comprises: placing the cross-linked polymer film on top of a perforated vial containing N-methylpyrrolidine in a sealed environment, and reacting at 70-80°C to allow the N-methylpyrrolidine to evaporate from the perforated vial and react with the chloro groups in the film.

[0014] According to the preparation method of the polymer, the method comprises: Step 1: dissolving biphenyl and N-methyl-4-piperidone in dichloromethane, then dropwise adding a solution of trifluoroacetic acid / trifluoromethanesulfonic acid in a volume ratio of 1:(5-15), reacting at 0-20°C for 12-24 hours, and then pouring into a 0.8-1.2 M K2CO3 aqueous solution; preferably, the step further includes washing with water and drying to obtain polybiphenyl piperidine; Step 2: dissolving the polybiphenyl piperidine in DMSO, then adding iodomethane, and reacting at 40-60°C for 48-96 hours to obtain a partially quaternized linear polybiphenyl piperidinium solution; the molar ratio of iodomethane to polybiphenyl piperidine is 0:1, 0.2:1, 0.4:1, 0.6:1 or 0.8:1; Step 3: Cross-linking the partially quaternized linear polybiphenylpiperidinium solution with cyanuric chloride at 40-60° C. to obtain a s-triazine cross-linked polybiphenylpiperidinium solution having residual chloro groups; the molar ratio of cyanuric chloride to residual piperidine groups is (0.5-1):1; the residual piperidine groups are the unquaternized piperidines in the linear polybiphenylpiperidinium in step 2; Step 4, pouring the s-triazine polybiphenyl piperidinium solution having residual chloro groups onto the substrate, and volatilizing the solvent at 40-50° C. in an inert gas atmosphere to obtain an s-triazine polybiphenyl piperidinium anion exchange membrane having residual chloro groups; Step 5: In a sealed environment, placing the s-triazine polybiphenylpiperidinium anion exchange membrane with residual chloro groups on top of a perforated vial containing N-methylpyrrolidine, and reacting at 70-80° C. to allow the N-methylpyrrolidine to evaporate from the perforated vial and react with the chloro groups in the membrane to obtain an s-triazine cross-linked polybiphenylpiperidinium film with end-capping groups, namely the polymer; the molar ratio of the N-methylpyrrolidine to the cyanuric chloride in step 3 is (1-20):1.

[0015] The preparation method of the ion exchange membrane of the present invention is simple to operate and has broad industrialization prospects.

[0016] In a third aspect, the present invention provides the use of the polymer in water electrolysis, preparation of ion exchange membranes, preparation of alkaline fuel cells or preparation of liquid flow batteries.

[0017] In a fourth aspect, the present invention provides a modified anion exchange membrane, which is made from the polymer.

[0018] In a fifth aspect, the present invention provides a method for preparing the modified anion exchange membrane, comprising: subjecting the polymer to ion exchange; Preferably, the preparation method of the modified anion exchange membrane comprises: soaking the polymer in a NaCl aqueous solution to obtain a chloride-ionized ion polymer membrane; and then soaking the chloride-ionized ion polymer membrane in an inorganic alkali aqueous solution to obtain the modified anion exchange membrane.

[0019] According to the preparation method of the modified anion exchange membrane, the inorganic alkali aqueous solution is a sodium hydroxide aqueous solution and / or a potassium hydroxide aqueous solution, and the concentration of the inorganic alkali aqueous solution is 0.5-2M.

[0020] Preferably, the soaking temperature is 60-90°C.

[0021] Preferably, after soaking for 2 to 3 hours, the inorganic alkali aqueous solution is replaced and the soaking is repeated 2 to 6 times.

[0022] In a sixth aspect, the present invention provides the use of the modified anion exchange membrane in water electrolysis, preparation of alkaline fuel cells or preparation of liquid flow batteries.

[0023] The s-triazine cross-linked polybiphenylpiperidinium hydroxide ion exchange membrane with specific end-capping groups of the present invention can be used as a membrane material for hydrogen production by electrolysis of water and for fuel cells.

[0024] The present invention introduces the end-capping agent by adopting a gas-solid reaction method, that is, the film reacts with the vaporized end-capping agent. This method has a positioning effect on the polymer molecular chain, so that when the end-capping reaction occurs, the static polymer chain and the dynamic end-capping agent are in a fixed-point reaction, thereby preventing the polymer chain from highly moving and self-crosslinking. In addition, by optimizing the end-capping agent to regulate the spatial structure of the triazine network cross-linking site, the stability of the film and the OH group are simultaneously improved. - The purpose of conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a synthetic route diagram of sPBP-MPY-G-OH in Example 1 provided by the present invention.

[0027] Figure 2 This is a synthetic route diagram of sPBP-MPY-L-OH in Comparative Example 1 provided by the present invention.

[0028] Figure 3 This is the synthesis route of sPBP-MPY-S-OH in Comparative Example 2 provided by the present invention.

[0029] Figure 4 This is the synthesis route of sPBP-MPI-G-OH in Comparative Example 3 provided by the present invention.

[0030] Figure 5 This is the synthesis route of sPBP-TMA-G-OH in Comparative Example 4 provided by the present invention.

[0031] Figure 6 This is the synthesis route of sPBP-TEA-G-OH in Comparative Example 5 provided by the present invention.

[0032] Figure 7 Schematic diagrams of the liquid-liquid reaction method, liquid-solid reaction method and gas-solid reaction method provided by the present invention; wherein (a) is a schematic diagram of the liquid-liquid reaction method, (b) is a schematic diagram of the liquid-solid reaction method, and (c) is a schematic diagram of the gas-solid reaction method.

[0033] Figure 8 It is a spatial structure diagram of the cross-linking site of the triazine network under different blocking groups provided by the present invention.

[0034] Figure 9 1 is a graph of ionic conductivity of the embodiments and comparative examples provided by the present invention.

[0035] Figure 10 It is a schematic diagram of the water electrolyzer device provided by the present invention.

[0036] Figure 11 This is a diagram of the water electrolysis test results provided by the present invention.

[0037] Figure 12 This is a comparison chart of water electrolysis test results provided by the present invention. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0039] Example 1 Preparation of N-methylpyrrolidine-terminated triazine network polybiphenylpiperidinium by gas-solid reaction method The synthesis route of N-methylpyrrolidine-terminated triazine network polybiphenylpiperidinium is as follows: Figure 1 shown.

[0040] The detailed synthesis method is as follows: (1) Preparation of precursor polymer (PMBP): 1.5000 g (9.7268 mmol) of biphenyl, 1.1007 g (9.7268 mmol) of N-methyl-4-piperidone, and 6 mL of CH2Cl2 were placed in a dry 100 mL two-necked flask and mixed uniformly with mechanical stirring in an ice bath. Subsequently, a mixed solution of 7.2 mL of TFSA and 0.75 mL of TFA was slowly added dropwise at the same temperature and a rotation speed of 400 rpm. After the addition was complete, the mixture was stirred at a low temperature at a rotation speed of 400 rpm for 3 h, 700 rpm for 30 min, and 900 rpm for 12 h, followed by the addition of 0.11 g (0.9727 mmol) of N-methyl-4-piperidone. After reacting for 20 min, the solution became viscous, and stirring was continued at a rotation speed of 1000 rpm for 3.5 h before the reaction was stopped.

[0041] The viscous solution was slowly poured into a beaker containing a 1 M K2CO3 aqueous solution and filtered to obtain a white fibrous precipitate. The solution was then stirred in a 1 M K2CO3 aqueous solution at 60°C for 3 h, after which the 1 M K2CO3 solution was replaced. This step was repeated three times, followed by stirring at 60°C for 12 h. The solution was then washed with deionized water until neutral, and then stirred in water at 80°C for 12 h. The resulting white polymer was dried in a vacuum oven at 60°C for 24 h and labeled PMBP for future use (yield 98%).

[0042] (2) Preparation of cross-linked polymers: First, a 20 mL capped vial was dried at 120°C for 6 hours and then filled with nitrogen. 0.1 g PMBP, 2.0-3.0 mL DMSO, and 0.0226 g CHI were added and reacted at 60°C for 48 hours and then at 80°C for another 48 hours, until the solution turned reddish-black, yielding solution PBP. Next, 0.02219 g cyanuric chloride was added to the solution and stirred at room temperature for 24 hours to yield a cross-linked poly(biphenylpiperidinium) solution containing residual chloro groups, designated sPBP.

[0043] (3) Preparation of N-methylpyrrolidine-terminated triazine network polymer membrane: A perforated vial containing 15 ml of N-methylpyrrolidine was then added to the sealed container containing the cross-linked polybiphenylpiperidinium film containing residual chloro groups. The reaction was continued at 80°C for 72 hours, allowing the N-methylpyrrolidine to evaporate from the perforated vial and react with the chloro groups in the film to produce an N-methylpyrrolidine-terminated ionic polymer film, designated sPBP-MPY-G.

[0044] (4) Preparation of Hydroxide-Ionized Pyridine-Terminated and Triazine Network Polymer Membranes: Finally, the prepared film (sPBP-MPY-G) was immersed in a 1 M NaCl aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent chloride-ionized ion polymer membrane; then the chloride-ionized ion polymer membrane was immersed in a 1 M KOH aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent hydroxide-ionized ion polymer membrane, which is sPBP-MPY-G-OH.

[0045] Test results: The hydroxide ion exchange membranes prepared in this example, including but not limited to sPBP-MPY-G-OH, have theoretical ion exchange capacities of 3.95 g / mmol. - The conductivity of the membrane was 261.2 mS / cm. After the membrane was immersed in 1 M NaOH solution at 80 ° C for 30 days, the OH - The conductivity hardly decreases.

[0046] Comparative Example 1 Preparation of N-methylpyrrolidine-terminated triazine network polybiphenylpiperidinium (sPBP-MPY-L-OH) by liquid-liquid reaction method The synthetic route of N-methylpyrrolidine-terminated triazine network polybiphenylpiperidinium is as follows: Figure 3 shown.

[0047] The detailed preparation method is as follows: (1) Preparation of precursor polymer (PMBP): 1.5000 g (9.7268 mmol) of biphenyl, 1.1007 g (9.7268 mmol) of N-methyl-4-piperidone, and 6 mL of CH2Cl2 were placed in a dry 100 mL two-necked flask and mixed uniformly with mechanical stirring in an ice bath. Subsequently, a mixed solution of 7.2 mL of trifluoromethanesulfonic acid (TFSA) and 0.75 mL of trifluoroacetic acid (TFA) was slowly added dropwise at 400 rpm at the same temperature. After the addition was complete, the mixture was stirred at 400 rpm for 3 h, 700 rpm for 30 min, and 900 rpm for 12 h at low temperature, followed by the addition of 0.11 g (0.9727 mmol) of N-methyl-4-piperidone. After 20 min of reaction, the solution became viscous, and stirring was continued at 1000 rpm for 3.5 h before the reaction was stopped.

[0048] The viscous solution was slowly poured into a beaker containing a 1 M K2CO3 aqueous solution and filtered to obtain a white fibrous precipitate. The solution was then stirred in a 1 M K2CO3 aqueous solution at 60°C for 3 h, after which the 1 M K2CO3 solution was replaced. This step was repeated three times, followed by stirring at 60°C for 12 h. The solution was then washed with deionized water until neutral, and then stirred in water at 80°C for 12 h. The resulting white polymer was dried in a vacuum oven at 60°C for 24 h and labeled PMBP for future use (yield 98%).

[0049] (2) Preparation of cross-linked polymers: First, a 20 mL capped vial was dried at 120°C for 6 hours and then filled with nitrogen. 0.1 g PMBP, 2.0-3.0 mL DMSO, and 0.0226 g CHI were added and reacted at 60°C for 48 hours and then at 80°C for another 48 hours, until the solution turned reddish-black, yielding solution PBP. Next, 0.02219 g cyanuric chloride was added to the solution and stirred at room temperature for 24 hours to yield a cross-linked poly(biphenylpiperidinium) solution containing residual chloro groups, designated sPBP.

[0050] (3) Preparation of N-methylpyrrolidine-terminated and triazine network polymer membranes: An excess of N-methylpyrrolidine was then added to the cross-linked poly(biphenylpiperidinium) solution containing residual chloro groups. The reaction was allowed to proceed at 80°C for 72 hours to obtain an N-methylpyrrolidine-terminated ionic polymer solution. Subsequently, a solution casting method was used to pour the casting solution onto a glass plate. The solvent was then evaporated at 30–120°C under nitrogen to obtain a black film, designated sPBP-MPY-L.

[0051] (4) Preparation of Hydroxide-Ionized Pyridine-Terminated and Triazine Network Polymer Membranes: Finally, the prepared film (sPBP-MPY-L) was immersed in a 1 M NaCl aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent chloride-ionized ion polymer membrane; the chloride-ionized ion polymer membrane was then immersed in a 1 M KOH aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent hydroxide-ionized ion polymer membrane, which is sPBP-MPY-L-OH.

[0052] Test results: The hydroxyl ion exchange membranes prepared in this comparative example, including but not limited to sPBP-MPY-L-OH, have a theoretical ion exchange capacity of 3.94 g / mmol. The anion exchange membranes correspond to OH at 80°C. - The conductivity of the membrane was 160.2 mS / cm. After the membrane was immersed in 1 M NaOH solution at 80 ° C for 30 days, the OH - The conductivity hardly decreases.

[0053] Comparative Example 2 Preparation of N-methylpyrrolidine-terminated triazine network polybiphenylpiperidinium by liquid-solid reaction method The synthetic route of N-methylpyrrolidine-terminated triazine network polybiphenylpiperidinium is as follows: Figure 3 shown.

[0054] The detailed synthesis method is as follows: (1) Preparation of precursor polymer (PMBP): 1.5000 g of biphenyl, 1.1007 g of N-methyl-4-piperidone, and 6 mL of CH2Cl2 were placed in a dry 100 mL two-necked flask and mixed uniformly with mechanical stirring in an ice bath. Subsequently, a mixed solution of 7.2 mL of TFSA and 0.75 mL of TFA was slowly added dropwise at this temperature and a rotation speed of 400 rpm. After the addition was completed, the mixture was stirred at a low temperature at 400 rpm for 3 h, 700 rpm for 30 min, and 900 rpm for 12 h, followed by the addition of 0.11 g of N-methyl-4-piperidone. After reacting for 20 min, the solution became viscous, and stirring was continued at 1000 rpm for 3.5 h before stopping the reaction.

[0055] The viscous solution was slowly poured into a beaker containing a 1 M K2CO3 aqueous solution and filtered to obtain a white fibrous precipitate. The solution was then stirred in a 1 M K2CO3 aqueous solution at 60°C for 3 h, after which the 1 M K2CO3 solution was replaced. This step was repeated three times, followed by stirring at 60°C for 12 h. The solution was then washed with deionized water until neutral, and then stirred in water at 80°C for 12 h. The resulting white polymer was dried in a vacuum oven at 60°C for 24 h and labeled PMBP for future use (yield 98%).

[0056] (2) Preparation of cross-linked polymers: First, a 20 mL capped vial was dried at 120°C for 6 hours and then filled with nitrogen. 0.1 g PMBP, 2.0-3.0 mL DMSO, and 0.0226 g CHI were added and reacted at 60°C for 48 hours and then at 80°C for another 48 hours, until the solution turned reddish-black, yielding PBP solution. Next, 0.02219 g cyanuric chloride was added to the solution and stirred at room temperature for 24 hours to yield a cross-linked poly(biphenylpiperidinium) solution containing residual chloro groups, designated sPBP.

[0057] (3) Preparation of N-methylpyrrolidine-terminated triazine network polymer membrane: Then, an excess of N-methylpyrrolidine liquid was added to the cross-linked polybiphenylpiperidinium film containing residual chloro groups, and the reaction was carried out at 80°C for 72 hours to obtain an N-methylpyrrolidine-terminated ionic polymer film, which was named sPBP-MPY-S.

[0058] (4) Preparation of triazine network polymer membrane terminated with hydroxide ionization N-methylpyrrolidine: Finally, the prepared film (sPBP-MPY-S) was immersed in a 1 M NaCl aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent chloride-ionized ion polymer membrane; the chloride-ionized ion polymer membrane was then immersed in a 1 M KOH aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent hydroxide-ionized ion polymer membrane, which is sPBP-MPY-S-OH.

[0059] Test results: The hydroxyl ion exchange membranes prepared in this comparative example, including but not limited to sPBP-MPY-S-OH, have a theoretical ion exchange capacity of 3.95 g / mmol. - The conductivity of the membrane was 211.3 mS / cm. After the membrane was immersed in 1 M NaOH solution at 80 ° C for 30 days, the OH- The conductivity hardly decreases.

[0060] Comparative Example 3 Preparation of N-methylpiperidine-terminated triazine network polybiphenylpiperidinium by gas-solid reaction method The synthesis route of N-methylpiperidine-terminated triazine network polybiphenylpiperidinium by gas-solid reaction is as follows: Figure 4 shown.

[0061] The detailed synthesis method is as follows: (1) Preparation of precursor polymer (PMBP): 1.5000 g (9.7268 mmol) of biphenyl, 1.1007 g (9.7268 mmol) of N-methyl-4-piperidone, and 6 mL of CH2Cl2 were placed in a dry 100-mL two-necked flask and mixed thoroughly with mechanical stirring in an ice bath. Subsequently, a mixed solution of 7.2 mL of TFSA and 0.75 mL of TFA was slowly added dropwise at 400 rpm at the same temperature. After the addition was complete, the mixture was stirred at 400 rpm for 3 h, 700 rpm for 30 min, and 900 rpm for 12 h at low temperature, followed by the addition of 0.11 g (0.9727 mmol) of N-methyl-4-piperidone. After 20 min of reaction, the solution became viscous, and stirring was continued at 1000 rpm for 3.5 h before the reaction was stopped.

[0062] The viscous solution was slowly poured into a beaker containing a 1 M K2CO3 aqueous solution and filtered to obtain a white fibrous precipitate. The solution was then stirred in a 1 M K2CO3 aqueous solution at 60°C for 3 h, after which the 1 M K2CO3 solution was replaced. This step was repeated three times, followed by stirring at 60°C for 12 h. The solution was then washed with deionized water until neutral, and then stirred in water at 80°C for 12 h. The resulting white polymer was dried in a vacuum oven at 60°C for 24 h and labeled PMBP for future use (yield 98%).

[0063] (2) Preparation of cross-linked polymers: First, a 20 mL capped vial was dried at 120°C for 6 hours and then filled with nitrogen. 0.1 g PMBP, 2.0-3.0 mL DMSO, and 0.0226 g CHI were added and reacted at 60°C for 48 hours and then at 80°C for another 48 hours, until the solution turned reddish-black, yielding PBP solution. Next, 0.02219 g cyanuric chloride was added to the solution and stirred at room temperature for 24 hours to yield a cross-linked poly(biphenylpiperidinium) solution containing residual chloro groups, designated sPBP.

[0064] (3) Preparation of N-methylpiperidine-terminated triazine network polymer membrane: A perforated vial containing excess N-methylpiperidine was then added to a sealed container containing a cross-linked poly(biphenylpiperidinium) film containing residual chloro groups. The reaction was then incubated at 80°C for 72 hours, allowing the N-methylpiperidine to evaporate from the perforated vial and react with the chloro groups in the film to produce an N-methylpiperidine-terminated ionic polymer film, designated sPBP-MPI-G.

[0065] (4) Preparation of triazine network polymer membrane terminated with N-methylpiperidine and hydroxide ionization: Finally, the prepared film (sPBP-MPI-G) was immersed in a 1 M NaCl aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent chloride-ionized ion polymer membrane; then the chloride-ionized ion polymer membrane was immersed in a 1 M KOH aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent hydroxide-ionized ion polymer membrane, namely sPBP-MPI-G-OH.

[0066] Test results: The hydroxyl ion exchange membranes prepared in this comparative example, including but not limited to sPBP-MPI-G-OH, have a theoretical ion exchange capacity of 3.9 g / mmol. The anion exchange membranes correspond to OH at 80°C. - The conductivity of the membrane was 96.4 mS / cm. After the membrane was immersed in 1 M NaOH solution at 80℃ for 30 days, the OH - The conductivity hardly decreases.

[0067] Comparative Example 4 Preparation of trimethylamine-terminated triazine network polybiphenylpiperidinium by gas-solid reaction method The synthesis route of trimethylamine-terminated triazine network polybiphenylpiperidinium by gas-solid reaction is as follows: Figure 5 shown.

[0068] The detailed synthesis method is as follows: (1) Preparation of precursor polymer (PMBP): 1.5000 g (9.7268 mmol) of biphenyl, 1.1007 g (9.7268 mmol) of N-methyl-4-piperidone, and 6 mL of CH2Cl2 were placed in a dry 100-mL two-necked flask and mixed thoroughly with mechanical stirring in an ice bath. Subsequently, a mixed solution of 7.2 mL of TFSA and 0.75 mL of TFA was slowly added dropwise at 400 rpm at the same temperature. After the addition was complete, the mixture was stirred at 400 rpm for 3 h, 700 rpm for 30 min, and 900 rpm for 12 h at low temperature, followed by the addition of 0.11 g (0.9727 mmol) of N-methyl-4-piperidone. After 20 min of reaction, the solution became viscous, and stirring was continued at 1000 rpm for 3.5 h before the reaction was stopped.

[0069] The viscous solution was slowly poured into a beaker containing a 1 M K2CO3 aqueous solution and filtered to obtain a white fibrous precipitate. The solution was then stirred in a 1 M K2CO3 aqueous solution at 60°C for 3 h, after which the 1 M K2CO3 solution was replaced. This step was repeated three times, followed by stirring at 60°C for 12 h. The solution was then washed with deionized water until neutral, and then stirred in water at 80°C for 12 h. The resulting white polymer was dried in a vacuum oven at 60°C for 24 h and labeled PMBP for future use (yield 98%).

[0070] (2) Preparation of cross-linked polymers: First, a 20 mL capped vial was dried at 120°C for 6 hours and then filled with nitrogen. 0.1 g PMBP, 2.0-3.0 mL DMSO, and 0.0226 g CHI were added and reacted at 60°C for 48 hours and then at 80°C for another 48 hours, until the solution turned reddish-black, yielding PBP solution. Next, 0.02219 g cyanuric chloride was added to the solution and stirred at room temperature for 24 hours to yield a cross-linked poly(biphenylpiperidinium) solution containing residual chloro groups, designated sPBP.

[0071] (3) Preparation of trimethylamine-terminated triazine network polymer membrane: A perforated vial containing excess trimethylamine was then added to a sealed container containing a cross-linked poly(biphenylpiperidinium) film containing residual chloro groups. The reaction was allowed to proceed at 25°C for one week, allowing the trimethylamine to evaporate from the vial and react with the chloro groups in the film to produce a trimethylamine-terminated ionomer film, designated sPBP-TMA-G.

[0072] (4) Preparation of trimethylamine-terminated triazine network polymer membrane with hydroxide ionization: Finally, the prepared film (sPBP-TMA-G) was immersed in a 1 M NaCl aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent chloride-ionized ion polymer membrane; then the chloride-ionized ion polymer membrane was immersed in a 1 M KOH aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent hydroxide-ionized ion polymer membrane, namely sPBP-TMA-G-OH.

[0073] Test results: The hydroxyl ion exchange membranes prepared in this comparative example, including but not limited to sPBP-TMA-G-OH, have theoretical ion exchange capacities of 4.04 g / mmol. - The conductivity of the membrane was 156.8 mS / cm. After the membrane was immersed in 1 M NaOH solution at 80 °C for 30 days, the OH content of the membrane was - The conductivity hardly decreases.

[0074] Comparative Example 5 Preparation of triethylamine-terminated triazine network polybiphenylpiperidinium by gas-solid reaction method The synthesis route of triethylamine-terminated triazine network polybiphenylpiperidinium by gas-solid reaction is as follows: Figure 6 shown.

[0075] The detailed synthesis method is as follows: (1) Preparation of precursor polymer (PMBP): 1.5000 g (9.7268 mmol) of biphenyl, 1.1007 g (9.7268 mmol) of N-methyl-4-piperidone, and 6 mL of CH2Cl2 were placed in a dry 100-mL two-necked flask and mixed thoroughly with mechanical stirring in an ice bath. Subsequently, a mixed solution of 7.2 mL of TFSA and 0.75 mL of TFA was slowly added dropwise at 400 rpm at the same temperature. After the addition was complete, the mixture was stirred at 400 rpm for 3 h, 700 rpm for 30 min, and 900 rpm for 12 h at low temperature, followed by the addition of 0.11 g (0.9727 mmol) of N-methyl-4-piperidone. After 20 min of reaction, the solution became viscous, and stirring was continued at 1000 rpm for 3.5 h before the reaction was stopped.

[0076] The viscous solution was slowly poured into a beaker containing a 1 M K2CO3 aqueous solution and filtered to obtain a white fibrous precipitate. The solution was then stirred in a 1 M K2CO3 aqueous solution at 60°C for 3 h, after which the 1 M K2CO3 solution was replaced. This step was repeated three times, followed by stirring at 60°C for 12 h. The solution was then washed with deionized water until neutral, and then stirred in water at 80°C for 12 h. The resulting white polymer was dried in a vacuum oven at 60°C for 24 h and labeled PMBP for future use (yield 98%).

[0077] (2) Preparation of cross-linked polymers: First, a 20 mL capped vial was dried at 120°C for 6 hours and then filled with nitrogen. 0.1 g PMBP, 2.0-3.0 mL DMSO, and 0.0226 g CHI were added and reacted at 60°C for 48 hours and then at 80°C for another 48 hours, until the solution turned reddish-black, yielding PBP solution. Next, 0.02219 g cyanuric chloride was added to the solution and stirred at room temperature for 24 hours to yield a cross-linked poly(biphenylpiperidinium) solution containing residual chloro groups, designated sPBP.

[0078] (3) Preparation of triethylamine-terminated triazine network polymer membrane: A perforated vial containing excess triethylamine was then added to a sealed container containing a cross-linked poly(biphenylpiperidinium) film containing residual chloro groups. The reaction was then allowed to proceed at 80°C for 72 hours, allowing the triethylamine to evaporate from the vial and react with the chloro groups in the film, yielding a triethylamine-terminated ionomer film, designated sPBP-TEA-G.

[0079] (4) Preparation of triethylamine-terminated triazine network polymer membrane with hydroxide ionization: Finally, the prepared film (sPBP-TEA-G) was immersed in a 1 M NaCl aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent chloride-ionized ion polymer membrane; the chloride-ionized ion polymer membrane was then immersed in a 1 M KOH aqueous solution at 80 °C for 2 to 5 hours, and then repeated 3 to 5 times to obtain a colorless and transparent hydroxide-ionized ion polymer membrane, which is sPBP-TEA-G-OH.

[0080] Test results: The hydroxyl ion exchange membranes prepared in this comparative example, including but not limited to sPBP-TEA-G-OH, have a theoretical ion exchange capacity of 3.89 g / mmol. The anion exchange membranes correspond to OH at 80°C. -The conductivity of the membrane was 234.0 mS / cm. After the membrane was immersed in 1 M NaOH solution at 80℃ for 30 days, the OH - The conductivity hardly decreases.

[0081] The difference between Example 1 and Comparative Examples 1 to 2 lies in the difference in the end-capping reaction step. In Comparative Example 1, the end-capping agent and the triazine network polybiphenyl piperidinium with a chloro group are both in liquid form, that is, the reaction systems are both liquid-liquid systems, which is called a liquid-liquid reaction method. In Comparative Example 2, the triazine network polybiphenyl piperidinium with a chloro group is first prepared into a film and then added to the liquid end-capping agent, that is, the reaction system is a liquid-solid system, which is called a liquid-solid reaction method. The difference between Example 1 and Comparative Example 2 is that the end-capping agent is in a gaseous state, that is, the reaction system is a gas-solid system, which is called a gas-solid reaction method. Schematic diagrams of the liquid-liquid reaction method, the liquid-solid reaction method, and the gas-solid reaction method are shown in FIG. Figure 7 .

[0082] On the one hand, end-capping agents such as N-methylpyrrolidine will react with residual chloro groups, and on the other hand, they will also catalyze the reaction of residual halogenated groups with unquaternized piperidine on the network molecular chain, causing excessive cross-linking. In the present invention, a triazine network polybiphenylpiperidinium with a chloro group is first prepared into a film to position the molecular chain; then, during the end-capping reaction, the static network molecular chain will react with a dynamic gas end-capping agent, and the gas-solid reaction method can prevent the interference of the alkaline end-capping agent on the molecular chain network degree. Therefore, compared with the gas-solid reaction method, the liquid-liquid reaction method and the liquid-solid reaction method have a stronger effect on the molecular chain network degree.

[0083] Meanwhile, in Comparative Examples 3 to 5, compared to Example 1, the corresponding capping agents are N-methylpiperidine (MPI), trimethylamine (TMA), and triethylamine (TEA), respectively. Under the premise of applying the gas-solid reaction method, these different capping groups facilitate the construction of different cavities at the crosslinking sites. The present invention surprisingly found that Example 1 is more likely to prepare triazine crosslinked polybiphenylpiperidinium with N-methylpyrrolidine capping, which has more regular crosslinking site cavities. The spatial structure diagram of the crosslinking site of the triazine network under different capping groups is shown in FIG. Figure 8 The present invention verifies the universality of the gas-solid reaction method by using different end-capping agents, and studies the spatial structure of the cross-linking sites of the triazine network regulated by different end-capping agents on the basis of this method. By constructing a more ordered cavity structure, the problem of the internal cavity becoming smaller due to the cross-linking of the molecular chain, which causes the ion conductivity to decrease, is solved, and the stability of the film and OH group are further improved at the same time. - Conductivity.

[0084] The ionic conductivity results of Example 1 and Comparative Examples 1 to 5 are shown in Figure 9 .

[0085] Test example 1. The present invention characterizes the water electrolysis performance of the N-methylpyrrolidine-terminated triazine network polybiphenylpiperidinium membrane prepared in Example 1.

[0086] It is well known that the use of non-platinum group metal catalysts can reduce the cost of hydrogen production. Therefore, we used inexpensive commercial NiMo foam as the cathode catalyst and Ni-NiFe / Ni2Fe as the anode catalyst in our water electrolysis experiments. Figure 10 Schematic diagram of the water electrolyzer device. From left to right, it shows the anode collector plate with flow channel, Ni-NiFe / Ni2Fe catalyst, membrane, NiMo foam, and cathode collector plate with flow channel. The test results of the electrolyzer at 60, 70, and 80 ° C under 1 M KOH conditions are shown in Figure 2. Figure 11 As shown. Figure 11 As shown in the figure, the current density of the electrolytic cell increases with the increase of temperature. The current density of the electrolytic cell at 2 V and 80 ° C is as high as 2.5 A / cm 2 , achieving the highest performance currently achievable using non-platinum group precious metal catalysts ( Figure 12 ). In addition, when a platinum group metal catalyst is used instead of commercial NiMo foam as the cathode catalyst in the water electrolysis test, the water electrolysis performance can reach a current density of up to 10.21 A / cm at 2 V. This is generally higher than the best performance reported in the literature.

[0087] 2. Mechanical properties and swelling rate of membrane Test method: Test method for tensile strength: GB / T 20042.3-20222; Swelling rate test method: GB / T 20042.3-20222.

[0088] The test results are shown in Table 1.

[0089] Table 1

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A polymer, characterized in that A compound having the general formula I: ； R is ; n is the unquaternized piperidine content, n=0~1; z=n / 2.

2. The polymer according to claim 1, characterized in that n is 0, 0.2, 0.4, 0.6 or 0.8; z is 0, 0.1, 0.2, 0.3 or 0.4; nz=n / 2, which is 0, 0.1, 0.2, 0.3 or 0.

4.

3. The method for preparing a polymer according to claim 1 or 2, characterized in that: include: (1) Biphenyl and N-methyl-4-piperidone are polymerized by superacid catalysis to obtain polybiphenylpiperidine; (2) reacting the polybiphenyl piperidine with iodomethane to prepare a partially quaternized polybiphenyl piperidinium; (3) cross-linking the partially quaternized polybiphenylpiperidinium with cyanuric chloride to obtain a cross-linked polymer film; (4) Immersing the cross-linked polymer film in a vaporized atmosphere of a pure capping agent to perform a capping reaction; the capping agent is N-methylpyrrolidine.

4. The method for preparing a polymer according to claim 3, wherein Step (4) comprises: placing the cross-linked polymer film on a perforated vial containing N-methylpyrrolidine in a sealed environment, and reacting at 70-80°C to allow the N-methylpyrrolidine to evaporate from the perforated vial and react with the chloro groups in the film.

5. The method for preparing a polymer according to claim 3 or 4, characterized in that: include: Step 1: dissolving biphenyl and N-methyl-4-piperidone in dichloromethane, then dropwise adding a solution of trifluoroacetic acid / trifluoromethanesulfonic acid in a volume ratio of 1:(5-15), reacting at 0-20°C for 12-24 hours, and then pouring into a 0.8-1.2 M K2CO3 aqueous solution; preferably, the step further includes washing with water and drying to obtain polybiphenyl piperidine; Step 2: dissolving the polybiphenyl piperidine in DMSO, then adding iodomethane, and reacting at 40-60° C. for 48-96 hours to obtain a partially quaternized linear polybiphenyl piperidinium solution; the molar ratio of iodomethane to polybiphenyl piperidine is 0:1, 0.2:1, 0.4:1, 0.6:1, or 0.8:1; Step 3: Cross-linking the partially quaternized linear polybiphenylpiperidinium solution with cyanuric chloride at 40-60° C. to obtain a s-triazine cross-linked polybiphenylpiperidinium solution having residual chloro groups; the molar ratio of cyanuric chloride to residual piperidine groups is (0.5-1):1; the residual piperidine groups are the unquaternized piperidines in the linear polybiphenylpiperidinium in step 2; Step 4, pouring the s-triazine polybiphenyl piperidinium solution having residual chloro groups onto the substrate, and volatilizing the solvent at 40-50° C. in an inert gas atmosphere to obtain an s-triazine polybiphenyl piperidinium anion exchange membrane having residual chloro groups; Step 5: In a sealed environment, placing the s-triazine polybiphenylpiperidinium anion exchange membrane with residual chloro groups on top of a perforated vial containing N-methylpyrrolidine, and reacting at 70-80° C. to allow the N-methylpyrrolidine to evaporate from the perforated vial and react with the chloro groups in the membrane to obtain an s-triazine cross-linked polybiphenylpiperidinium film with end-capping groups, namely the polymer; the molar ratio of the N-methylpyrrolidine to the cyanuric chloride in step 3 is (1-20):

1.

6. Use of the polymer according to claim 1 or 2 or the polymer obtained by the preparation method according to any one of claims 3 to 5 in water electrolysis, preparation of ion exchange membranes, preparation of alkaline fuel cells or preparation of liquid flow batteries.

7. A modified anion exchange membrane, characterized in that: The polymer is prepared from the polymer described in claim 1 or 2 or the polymer prepared by the preparation method according to any one of claims 3 to 5.

8. The method for preparing the modified anion exchange membrane according to claim 7, characterized in that: include: ion-exchanging the polymer according to claim 1 or 2; Preferably, the method for preparing the modified anion exchange membrane comprises: soaking the polymer according to claim 1 or 2 in a NaCl aqueous solution to obtain a chloride-ionized ion polymer membrane; The chloride-ionized ionomer membrane is then immersed in an inorganic base aqueous solution.

9. The method for preparing a modified anion exchange membrane according to claim 8, wherein: The inorganic alkali aqueous solution is a sodium hydroxide aqueous solution and / or a potassium hydroxide aqueous solution, and the concentration of the inorganic alkali aqueous solution is 0.5 to 2M; Preferably, the soaking temperature is 60-90°C; Preferably, after soaking for 2 to 3 hours, the inorganic alkali aqueous solution is replaced and the soaking is repeated 2 to 6 times.

10. Use of the modified anion exchange membrane according to claim 7 or the modified anion exchange membrane prepared by the preparation method according to claim 8 or 9 in water electrolysis, preparation of alkaline fuel cells or preparation of liquid flow batteries.

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