Branched polyaryl piperidine polymer as well as preparation method and application thereof

Abstract

The invention relates to a branched polyaryl piperidine polymer as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving a linear structure phenyl monomer, a branched structure phenyl monomer, 1, 2-diphenylethane and N-methyl-4-piperidone to obtain a precursor polymer solution; dropwise adding trifluoroacetic acid and trifluoromethanesulfonic acid to obtain a branched polyaromatic piperidine polymer precursor; and dissolving the polyaromatic piperidine, adding methyl iodide and potassium carbonate, reacting to obtain a quaternized branched polyaromatic piperidine polymer, and carrying out membrane treatment and alkali treatment processes to obtain the anion exchange membrane. By introducing the branched monomer, the problem of mutual connection between linear main chains of a traditional polymer is solved, formation of a microphase separation structure in the polymer is promoted, and high dimensional stability and high mechanical performance of the anion exchange membrane are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production by electrolysis of water, and in particular relates to a branched polyarylpiperidine polymer and a preparation method and application thereof. Background Art

[0002] Hydrogen technologies, including fuel cells and hydrogen generation systems (water electrolysis), have been proposed as potential solutions for achieving carbon neutrality within the next few decades. Anion exchange membrane fuel cells and water electrolyzers operating under alkaline conditions can utilize non-precious metal catalysts and hydrocarbon-based polyelectrolytes, significantly reducing the cost of energy devices. While significant progress has been made in the development of anion exchange membrane water electrolyzers, improvements are still needed, particularly in terms of in-situ durability and power density.

[0003] Over the past few decades, significant efforts have been made to develop high-performance poly(arylpiperidine) anion exchange membranes by adjusting the polymer backbone, cationic groups, and modification strategies. Despite significant progress in this field, most anion exchange membranes still face challenges in physical stability, electrical conductivity, and dimensional stability.

[0004] Two main strategies have been employed to improve the mechanical properties of membranes, which are related to the molecular weight and chemical structure of the polymer. These include cross-linking and reinforcement techniques. However, these approaches often sacrifice the ionic conductivity of anion exchange membranes, resulting in reduced power density in energy devices containing such membranes. Recently, researchers have demonstrated that the introduction of highly reactive monomers can enable the use of high-molecular-weight polymers for robust membranes. Therefore, highly reactive branching units have emerged as an option to address the issue of poor mechanical properties.

[0005] Furthermore, the trade-off between conductivity and dimensional stability is another obstacle hindering the sustainable operation of anion exchange membrane water electrolyzers. Various strategies, such as cross-linking, grafting, and block copolymer structures, have been reported to address this thorny issue. However, these approaches are limited in the choice of polymer backbone or complex synthesis processes. On the other hand, branched structures are considered a simple way to resolve this dilemma. Wu Xingyu et al. reported a triphenylbenzene-branched poly(p-triphenylpiperidinium) with improved dimensional stability (25.9% vs. 33.2% swelling ratio) and conductivity (146.7 mS cm-1 vs. 137.7 mS cm-1) compared to its linear counterpart. However, the planar structure of triphenylbenzene typically results in a compact and dense polymer structure, which limits gas and water transport, especially for ionomers in anion exchange membrane water electrolyzers. In addition, the planar structure of triphenylbenzene increases the risk of phenyl adsorption on the catalyst surface, resulting in low electrode activity.

[0006] We proposed a series of branched polymers based on a poly(fluorene / dibenzyl coarylpiperidinium) backbone by introducing different branched phenyl monomers, including 9-phenylcarbazole and 9,9-diphenylfluorene (highly rigid, branched structures). We found that the highly rigid branched monomers have a significant advantage in generating free volume, which in turn promotes the formation of conductive pathways and facilitates the adsorption and transport of water molecules within the membrane.

[0007] An existing patent discloses a branched block polyarylpiperidine polymer, an anion exchange membrane, and its preparation and application. Leveraging the significant convenience of introducing branched structural units into linear polymers for large-scale sample synthesis, the patent develops a polymer synthesis method that combines branched structural units, block linear structural units, and linear monomers to produce anion exchange membranes. However, the synthesis process of these block linear structural units involves numerous steps, significantly increasing the risk and complexity of sample preparation. Furthermore, the ionic conductivity of the anion exchange membranes synthesized by this method is far inferior to that of the currently mainstream main-chain anion exchange membranes.

[0008] The existing branched polyaryl piperidine polymers have a planar structure, which makes the polymer structure compact and dense, restricting the transmission of gas and water. The present invention solves the problem of internal structural entanglement of traditional branched polyaryl piperidine polymers by introducing a small amount of branched phenyl monomers into the structure, achieving the effect of generating free volume, promoting the formation of conductive paths, and promoting the adsorption and transport of water molecules in the membrane. Summary of the Invention

[0009] The present invention addresses the problems existing in the prior art by providing a branched polyarylpiperidine polymer, an anion exchange membrane, and its preparation method and application. The polymer comprises branched structural units and block linear structural units, and an anion exchange membrane can be obtained through further membrane treatment and alkali treatment. The present invention provides a simple process for preparing anion exchange membranes with high yield, achieving high dimensional stability and mechanical properties, enabling applications in high-performance and highly stable electrolytic cells.

[0010] The purpose of the present invention can be achieved by the following solutions:

[0011] The present invention provides a branched polyarylpiperidine polymer having the following structural formula:

[0012]

[0013] in, include

[0014] Ar1-1 is One or more of the following;

[0015] Ar1-2 is

[0016] Ar2 is

[0017] Ar2 is preferably

[0018] In the structural formula, Ar1 includes Ar1-1 and Ar1-2; It is a random mixed connection.

[0019] In the general structural formula, the molar ratio of Ar1-1, Ar2, and Ar1-2 is 12 to 18: 0.4 to 2: 2 to 8. Ar1 is a linear phenyl group, and Ar2 is a branched phenyl group.

[0020] In the general structural formula, n is 85-97.5, and n% represents the molar percentage of the Ar1 group (Ar1+Ar2).

[0021] The present invention provides a method for preparing a branched polyarylpiperidine polymer, comprising the following steps:

[0022] S1, dissolving a linear phenyl monomer (Ar1-1), a branched phenyl monomer (Ar2), 1,2-diphenylethane and N-methyl-4-piperidone in an organic solvent 1, and stirring and mixing to obtain a precursor polymer solution; adding trifluoroacetic acid and trifluoromethanesulfonic acid dropwise to the precursor polymer solution, stirring and reacting, and obtaining a precipitate as a branched polyaromatic piperidine polymer precursor;

[0023] S2. Dissolving the branched polyaromatic piperidine polymer precursor in organic solvent 2, adding methyl iodide and potassium carbonate, and stirring to react. The resulting precipitate is the quaternized branched polyaromatic piperidine polymer.

[0024] As one embodiment of the present invention, in step S1, the linear phenyl monomer (Ar1-1) includes one or more of biphenyl (I), p-terphenyl (II), and fluorene (III). The structural formulas of the linear phenyl monomer (Ar1-1) are shown below I-III:

[0025]

[0026] As one embodiment of the present invention, in step S1, the branched phenyl monomer (Ar2) includes one or more of 9,9-diphenylfluorene (IV) and 9-phenylcarbazole (V). The structural formula of the branched phenyl monomer (Ar2) is shown below as IV-V:

[0027]

[0028] Branched structure phenyl monomer (Ar2) is preferably 9-phenylcarbazole (V).9-phenylcarbazole, compared to the branching center of insufficient rigidity, such as triphenylbenzene, has the very high fluorenyl part of rigidity, ensures the rigidity of branching as a whole, promotes the generation of the free volume in the anion exchange membrane, further improves the specific conductivity and the mechanical property of anion exchange membrane.9-phenylcarbazole, compared to the branching center of excessive rigidity, such as triptycene, has the flexible phenyl part, avoids the infringement of branching center to the flexibility of membrane as a whole in the synthesis, reduces the difficulty of synthesis.Simultaneously, the existence of nitrogen atom center has controlled the ratio of flexible part, to prevent the rigidity of branching center from being too low.

[0029] The structural formula of 1,2-diphenylethane:

[0030] As one embodiment of the present invention, in step S1, the molar ratio of the linear phenyl monomer (Ar1-1), the branched phenyl monomer (Ar2), and 1,2-diphenylethane (Ar1-2) is 12-18:0.4-2:2-8. The molar ratio of the linear phenyl monomer (Ar1-1) and N-methyl-4-piperidone is 22-26:32-36.

[0031] As one embodiment of the present invention, in step S1, the organic solvent 1 is dichloromethane (purity greater than 99.5%). The linear phenyl monomer (Ar1-1), N-methyl-4-piperidone, and the organic solvent 1 are used in a ratio of 22-26 mmol: 32-36 mmol: 20-30 ml.

[0032] As an embodiment of the present invention, in step S1, the stirring and mixing temperature is -5 to -2°C, preferably -3°C, and the time is 10 to 40 minutes, preferably 30 minutes.

[0033] As an embodiment of the present invention, in step S1, the volume ratio of trifluoroacetic acid (TFA), trifluoromethanesulfonic acid (TFSA) and organic solvent 1 is 3-4:20-30:20-30, preferably 3:20:20.

[0034] As an embodiment of the present invention, in step S1, the stirring reaction time is 2 to 3 hours.

[0035] In one embodiment of the present invention, in step S1, a precipitate (branched polyaromatic piperidine polymer precursor) is obtained by pouring the stirred reaction solution into water. The resulting precipitate is then washed and dried. Washing is performed 3-5 times with deionized water, and drying is performed by vacuum drying at 75-85°C for 20-30 hours.

[0036] As an embodiment of the present invention, in step S2, the ratio of the branched polyaromatic piperidine polymer precursor to the organic solvent 2 is 1 g: 10-20 mL. The organic solvent 2 is dimethyl sulfoxide (with a purity greater than 99.9%).

[0037] As an embodiment of the present invention, in step S2, the usage ratio of the branched polyaromatic piperidine polymer precursor, methyl iodide, and potassium carbonate is 1 g: 1.5-2.5 ml: 1.5-2.5 g.

[0038] As an embodiment of the present invention, in step S2, the stirring reaction time is 20 to 30 hours and the stirring reaction is carried out at room temperature (20 to 25° C.) in the dark.

[0039] In one embodiment of the present invention, in step S2, the precipitate (quaternized branched polyaromatic piperidine polymer) is obtained by adding the stirred reaction solution to ethyl acetate. The resulting precipitate is washed and dried. The washing step is performed 3-5 times with deionized water, and the drying step is performed by vacuum drying at 75-85°C for 20-30 hours.

[0040] The present invention provides an application of the branched polyarylpiperidine polymer in preparing an anion exchange membrane.

[0041] The present invention provides a method for preparing an anion exchange membrane, comprising the following steps:

[0042] The quaternized branched polyaromatic piperidine polymer is dissolved in an organic solvent 2, the filtered polymer solution is spread on a carrier, and dried to obtain I - Type membrane; - The membrane is peeled off and soaked in alkali solution to obtain an anion exchange membrane (OH - type film).

[0043] As one embodiment of the present invention, the usage ratio of the quaternized branched polyaromatic piperidine polymer and the organic solvent 2 is 0.2 g: 3-8 ml.

[0044] As one embodiment of the present invention, the filtration is performed using a 0.45 μm polytetrafluoroethylene (PTFE) filter.

[0045] As one embodiment of the present invention, the drying is carried out at 70-90° C. for 20-30 hours.

[0046] As one embodiment of the present invention, the obtained - The thickness of the mold film is 10 to 30 μm.

[0047] As an embodiment of the present invention, the soaking temperature is 65°C and the soaking time is 10 to 15 hours. The soaking alkali solution is 1M KOH solution. - The membrane was stored in deionized water with nitrogen.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) By adopting a one-pot method to polymerize polymer monomers under superacid conditions and innovatively introducing branched monomers, the problems of complex traditional polymer synthesis processes, long synthesis time, and low yield were solved, and large-scale preparation of polymer precursors with stable chemical composition was achieved.

[0050] (2) By introducing branched monomers, the problem of interconnection between the linear main chains of traditional polymers is solved, the formation of microphase separation structure inside the polymer is promoted, and high dimensional stability and high mechanical properties of the anion exchange membrane are achieved.

[0051] (3) By introducing high steric hindrance, high rigidity and hydrophobic branched monomers, the entanglement problem between the linear main chains of traditional polymers is solved, a larger free volume and spatial steric hindrance are provided, and high ionic conductivity and high alkaline stability of the anion exchange membrane are achieved, thereby further improving the water electrolysis performance of the anion exchange membrane electrolyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0053] Figure 1 is a process flow chart;

[0054] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the branched polyarylpiperidine polymer precursor prepared in Example 1;

[0055] Figure 3 This is the hydrogen nuclear magnetic resonance spectrum of the quaternized branched polyaromatic piperidine polymer prepared in Example 1;

[0056] Figure 4 The stress-strain curves of the anion exchange membranes prepared in Examples 1-2 and Comparative Example 1;

[0057] Figure 5 Ionic conductivity of the anion exchange membranes prepared in Examples 1-2 and Comparative Example 1 at different temperatures;

[0058] Figure 6 The electrochemical performance of branched polyarylpiperidine polymer anion exchange membrane prepared in Example 1 for oxygen evolution in electrolyzers (AEMWEs);

[0059] Figure 7 Long-term stability test of the branched polyarylpiperidine polymer anion exchange membrane prepared in Example 1 in electrolyzers (AEMWEs);

[0060] Figure 8 This is the hydrogen nuclear magnetic resonance spectrum of the branched polyarylpiperidine polymer precursor prepared in Example 2;

[0061] Figure 9 This is the hydrogen nuclear magnetic resonance spectrum of the quaternized branched polyaromatic piperidine polymer prepared in Example 2;

[0062] Figure 10 The electrochemical performance of branched polyarylpiperidine polymer anion exchange membrane prepared in Example 2 for oxygen evolution in electrolyzers (AEMWEs);

[0063] Figure 11 This is a long-term stability test of the branched polyarylpiperidine polymer anion exchange membrane prepared in Example 2 in electrolyzers (AEMWEs). DETAILED DESCRIPTION

[0064] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, provide detailed implementation methods and specific operating procedures, and will help those skilled in the art to further understand the present invention. It should be pointed out that the scope of protection of the present invention is not limited to the following embodiments, and a number of adjustments and improvements made under the premise of the concept of the present invention all fall within the scope of protection of the present invention.

[0065] The present invention relates to a branched polyarylpiperidine polymer and its preparation into anion exchange membrane. The preparation process is as follows: Figure 1 As shown, the preparation steps are as follows:

[0066] Step 1: Prepare a branched polyaryl piperidine polymer precursor: Add a predetermined amount of a linear phenyl monomer, a branched phenyl monomer, and N-methyl-4-piperidone to the resulting solution, adding organic solvent 1 to obtain a precursor polymer solution. Trifluoroacetic acid and trifluoromethanesulfonic acid are added dropwise to allow a reaction to proceed. After sufficient reaction, the solution is washed and dried to obtain a branched polyaryl piperidine polymer precursor.

[0067] Step 2, preparing a quaternized branched polyaryl piperidine polymer: dissolving the branched polyaryl piperidine polymer precursor obtained above in organic solvent 2, stirring, pouring a certain amount of iodomethane and potassium carbonate into the obtained solution, and after sufficient reaction, washing and drying to obtain a quaternized branched polyaryl piperidine polymer.

[0068] Step 3: Prepare an anion exchange membrane: Dissolve the quaternized branched polyarylpiperidine polymer in organic solvent 2, filter, spread, and dry to obtain a type I membrane. Soak the type I membrane in alkaline solution to obtain an anion exchange membrane.

[0069] In step 1, the precursor polymer solution is prepared as follows: a certain amount and a certain ratio of the aforementioned linear phenyl monomer, branched phenyl monomer, and N-methyl-4-piperidone are weighed, and the aforementioned dichloromethane is poured into the mixture, and the mixture is stirred thoroughly to obtain a precursor polymer solution containing different types of branched phenyl monomers;

[0070] In step 1, the preparation process of the branched polyarylpiperidine polymer precursor is as follows: a certain amount of trifluoroacetic acid and trifluoromethanesulfonic acid are added to the above-mentioned precursor polymer solution, and the mixture is stirred thoroughly during the process. The temperature of the mixed solution is controlled within a certain range to obtain a viscous precursor polymer mixture. The precursor polymer mixture is repeatedly washed with water three times, dried in a vacuum drying oven overnight, and the product is collected to obtain a branched polyarylpiperidine polymer precursor.

[0071] In step 2, the preparation process of the quaternized branched polyaryl piperidine polymer is as follows: the branched polyaryl piperidine polymer precursor obtained above is dissolved in the aforementioned dimethyl sulfoxide, and a certain amount of iodomethane and potassium carbonate are added, and the mixture is stirred thoroughly during the process. The reaction is protected from light to obtain a quaternized polymer mixture. The quaternized polymer mixture is repeatedly washed three times with ethyl acetate and water, dried in a vacuum drying oven overnight, and the product is collected to obtain a quaternized branched polyaryl piperidine polymer.

[0072] In step 3, the anion exchange membrane preparation process is as follows: the quaternized polyarylpiperidine polymer obtained above is dissolved in the aforementioned dimethyl sulfoxide, filtered, spread on a glass plate, and dried to obtain a type I membrane. The type I membrane is then soaked in an alkaline solution and washed to obtain an anion exchange membrane.

[0073] Example 1

[0074] (1) Dissolve terphenyl (5.745 g, 24.948 mmol), 1,2-diphenylethane (1.515 g, 8.316 mmol), 9,9-diphenylfluorene (0.636 g, 2 mmol) and N-methyl-4-piperidone (3.87 g, 34.2 mmol) in dichloromethane (24 ml) and stir at -3 °C for 30 min to obtain a light green mixed solution. TFA (3.6 ml) and TFSA (24 ml) are added dropwise thereto and stirred for 2.5 h until the color of the mixed solution changes from light green to dark brown. The mixed solution is poured into 500 ml of deionized water to precipitate a white polymer. Then wash with deionized water three times and vacuum dry at 80 °C for 24 h to obtain a branched polyaromatic piperidine polymer precursor. The nuclear magnetic resonance hydrogen spectrum is as follows: Figure 2 As shown;

[0075] (2) Dissolve the branched polyaromatic piperidine polymer precursor (1 g) in dimethyl sulfoxide (16 mL). Add iodomethane (2 ml) and potassium carbonate (2 g) under stirring at room temperature, and stir in the dark for 24 h at room temperature. After the reaction is completed, add it to excess ethyl acetate to obtain a white precipitate, wash it three times, filter it, wash it three times with deionized water, and dry it in a vacuum at 80°C for 24 h to obtain a quaternized branched polyaromatic piperidine polymer. The H NMR spectrum is as follows: Figure 3 As shown;

[0076] (3) The quaternized branched polyaromatic piperidine polymer (0.2 g) was dissolved in dimethyl sulfoxide (5 ml). The polymer solution was filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter and cast on a clean glass plate (6 cm*6 cm). The solution was dried at 80°C for 24 h to completely remove the residual solvent and obtain a 15 μm thick I - Type film;

[0077] (4) Will I - The OH-type membrane was peeled off from the glass plate and immersed in 1M KOH solution at 60℃ for 12h to obtain the OH-type membrane. It was washed with deionized water three times. In order to avoid CO2 contamination and carbonate formation, the OH - The membrane was stored in deionized water with nitrogen.

[0078] Example 2 (Preferred Scheme 1: Replacing the Type of Branched Phenyl Monomers)

[0079] (1) Dissolve terphenyl (5.745 g, 24.948 mmol), 1,2-diphenylethane (1.515 g, 8.316 mmol), 9-phenylcarbazole (0.487 g, 2 mmol) and N-methyl-4-piperidone (3.87 g, 34.2 mmol) in dichloromethane (24 ml) and stir at -3 °C for 30 min to obtain a light green mixed solution. TFA (3.6 ml) and TFSA (24 ml) are added dropwise thereto and stirred for 2.5 h until the color of the mixed solution changes from light green to dark green. The mixed solution is poured into 500 ml of deionized water to precipitate a white polymer. Then wash with deionized water three times and vacuum dry at 80 °C for 24 h to obtain a branched polyaromatic piperidine polymer precursor. The nuclear magnetic resonance hydrogen spectrum is as follows: Figure 8 As shown;

[0080] (2) Dissolve the branched polyaromatic piperidine polymer precursor (1 g) in dimethyl sulfoxide (16 mL). Add iodomethane (2 ml) and potassium carbonate (2 g) under stirring at room temperature, and stir in the dark for 24 h at room temperature. After the reaction is completed, add it to excess ethyl acetate to obtain a white precipitate, wash it three times, filter it, wash it three times with deionized water, and dry it in a vacuum at 80°C for 24 h to obtain a quaternized branched polyaromatic piperidine polymer. The H NMR spectrum is as follows: Figure 9 As shown;

[0081] (3) The quaternized branched polyaromatic piperidine polymer (0.2 g) was dissolved in dimethyl sulfoxide (5 ml). The polymer solution was filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter and cast on a clean glass plate (6 cm*6 cm). The solution was dried at 80°C for 24 h to completely remove the residual solvent and obtain a 15 μm thick I - Type film;

[0082] (4) Will I - The OH-type membrane was peeled off from the glass plate and immersed in 1M KOH solution at 60℃ for 12h to obtain the OH-type membrane. It was washed with deionized water three times. In order to avoid CO2 contamination and carbonate formation, the OH - The membrane was stored in deionized water with nitrogen.

[0083] Comparative Example 1 (phenyl monomer without branched structure)

[0084] The preparation method of the present invention is substantially the same as that of Example 2, except that 9-phenylcarbazole is not added.

[0085] (1) Dissolve terphenyl (5.745 g, 24.948 mmol), 1,2-diphenylethane (1.515 g, 8.316 mmol) and N-methyl-4-piperidone (3.87 g, 34.2 mmol) in dichloromethane (24 ml) and stir at -3 °C for 30 min to obtain a light green mixed solution. TFA (3.6 ml) and TFSA (24 ml) are added dropwise thereto and stirred for 2.5 h until the color of the mixed solution changes from light green to dark green. The mixed solution is poured into 500 ml of deionized water to precipitate a white polymer. The mixture is then washed three times with deionized water and dried in vacuum at 80 °C for 24 h to obtain a branched polyaromatic piperidine polymer precursor.

[0086] (2) Dissolve the branched polyaromatic piperidine polymer precursor (1 g) in dimethyl sulfoxide (16 mL). Add iodomethane (2 ml) and potassium carbonate (2 g) under stirring at room temperature, and stir in the dark for 24 h at room temperature. After the reaction is completed, add it to an excess of ethyl acetate to obtain a white precipitate, wash it three times, filter it, wash it three times with deionized water, and dry it in a vacuum at 80°C for 24 h to obtain a quaternized branched polyaromatic piperidine polymer;

[0087] (3) The quaternized branched polyaromatic piperidine polymer (0.2 g) was dissolved in dimethyl sulfoxide (5 ml). The polymer solution was filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter and cast on a clean glass plate (6 cm*6 cm). The solution was dried at 80°C for 24 h to completely remove the residual solvent and obtain a 15 μm thick I - Type film;

[0088] (4) Will I - The OH-type membrane was peeled off from the glass plate and immersed in 1M KOH solution at 60℃ for 12h to obtain the OH-type membrane. It was washed with deionized water three times. In order to avoid CO2 contamination and carbonate formation, the OH - The membrane was stored in deionized water with nitrogen.

[0089] Comparative Example 2

[0090] The preparation method of the present invention is substantially the same as that of Example 2, except that no 1,2-diphenylethane is added.

[0091] (1) Dissolve p-terphenyl (5.745 g, 24.948 mmol), 9-phenylcarbazole (0.487 g, 2 mmol) and N-methyl-4-piperidone (3.87 g, 34.2 mmol) in dichloromethane (24 ml) and stir at -3 °C for 30 min to obtain a light green mixed solution. TFA (3.6 ml) and TFSA (24 ml) are added dropwise thereto and stirred for 2.5 h until the color of the mixed solution changes from light green to dark green. The mixed solution is poured into 500 ml of deionized water to precipitate a white polymer. The mixture is then washed three times with deionized water and vacuum dried at 80 °C for 24 h to obtain a branched polyaromatic piperidine polymer precursor.

[0092] (2) Dissolve the branched polyaromatic piperidine polymer precursor (1 g) in dimethyl sulfoxide (16 mL). Add iodomethane (2 ml) and potassium carbonate (2 g) under stirring at room temperature, and stir in the dark for 24 h at room temperature. After the reaction is completed, add it to an excess of ethyl acetate to obtain a white precipitate, wash it three times, filter it, wash it three times with deionized water, and dry it in a vacuum at 80°C for 24 h to obtain a quaternized branched polyaromatic piperidine polymer;

[0093] (3) The quaternized branched polyaromatic piperidine polymer (0.2 g) was dissolved in dimethyl sulfoxide (5 ml). The polymer solution was filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter and cast on a clean glass plate (6 cm*6 cm). The solution was dried at 80°C for 24 h to completely remove the residual solvent and obtain a 15 μm thick I - Type film;

[0094] (4) Will I - The OH-type membrane was peeled off from the glass plate and immersed in 1M KOH solution at 60℃ for 12h to obtain the OH-type membrane. It was washed with deionized water three times. In order to avoid CO2 contamination and carbonate formation, the OH - The membrane was stored in deionized water with nitrogen.

[0095] The molecular weight of the polymer prepared by this method is too small, and a block solid cannot be precipitated during the first step of synthesis, which does not meet the subsequent film formation requirements.

[0096] Comparative Example 3

[0097] The preparation method of the present invention is basically the same as that of Example 2, except that 9-phenylcarbazole is replaced with an equal molar amount of 2,4,6-triphenyl-1,3,5-triazine; the structural formula is as follows:

[0098]

[0099] (1) Dissolve terphenyl (5.745 g, 24.948 mmol), 1,2-diphenylethane (1.515 g, 8.316 mmol), 2,4,6-triphenyl-1,3,5-triazine (0.487 g, 2 mmol) and N-methyl-4-piperidone (3.87 g, 34.2 mmol) in dichloromethane (24 ml) and stir at -3 °C for 30 min to obtain a light green mixed solution. TFA (3.6 ml) and TFSA (24 ml) are added dropwise thereto and stirred for 2.5 h until the color of the mixed solution changes from light green to dark green. The mixed solution is poured into 500 ml of deionized water to precipitate a white polymer. Then, the mixture is washed three times with deionized water and vacuum dried at 80 °C for 24 h to obtain a branched polyaromatic piperidine polymer precursor.

[0100] (2) Dissolve the branched polyaromatic piperidine polymer precursor (1 g) in dimethyl sulfoxide (16 mL). Add iodomethane (2 ml) and potassium carbonate (2 g) under stirring at room temperature, and stir in the dark for 24 h at room temperature. After the reaction is completed, add it to an excess of ethyl acetate to obtain a white precipitate, wash it three times, filter it, wash it three times with deionized water, and dry it in a vacuum at 80°C for 24 h to obtain a quaternized branched polyaromatic piperidine polymer;

[0101] (3) The quaternized branched polyaromatic piperidine polymer (0.2 g) was dissolved in dimethyl sulfoxide (5 ml). The polymer solution was filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter and cast on a clean glass plate (6 cm*6 cm). The solution was dried at 80°C for 24 h to completely remove the residual solvent and obtain a 15 μm thick I - Type film;

[0102] (4) Will I - The OH-type membrane was peeled off from the glass plate and immersed in 1M KOH solution at 60℃ for 12h to obtain the OH-type membrane. It was washed with deionized water three times. In order to avoid CO2 contamination and carbonate formation, the OH - The membrane was stored in deionized water with nitrogen.

[0103] Comparative Example 4

[0104] The preparation method of the present invention is substantially the same as that of Example 2, except that 1,2-diphenylethane is replaced by an equimolar amount of biphenyl.

[0105] Comparative Example 5

[0106] The preparation method of the present invention is substantially the same as that of Example 2, except that 1,2-diphenylethane is replaced by an equimolar amount of p-terphenyl.

[0107] Comparative Examples 4-5 are similar to Comparative Example 2. The molecular weight of the polymer prepared by this method is too small, and no bulk solid can be precipitated in the first step of synthesis, which does not meet the subsequent film formation requirements.

[0108] Performance testing method:

[0109] (1) Water absorption

[0110] (2) Swelling

[0111] The membrane sample was soaked in 1M NaOH for 48 hours for ion exchange, then washed several times with deionized water to remove excess alkali solution to obtain an OH-type AEM sample. The membrane sample was stored in deionized water for use. The membrane sample was cut into squares (2*2cm) and soaked in deionized water for 12 hours. The membrane sample was then removed, and the water droplets on the membrane surface were wiped dry with filter paper. The mass (M1) and length (L1) of the membrane sample were immediately tested. The wet membrane sample was then placed in a vacuum drying oven and vacuum dried to constant weight. Its dry weight (M2) and length (L2) were tested. The swelling ratio (Sr) and water absorption (Wu) of the membrane can be calculated using the following formula:

[0112] Sr (%) = (L1-L2) / L2

[0113] Wu (%) = (M1-M2) / M2

[0114] (3) Conductivity at 60°C

[0115] The ionic conductivity of the membrane was measured using a four-probe alternating current (AC) impedance analyzer over a frequency range of 0.1 to 100 kHz. Rectangular samples (1 × 3 cm) of the OH- form were placed on two platinum electrodes and then assembled in a homemade conductive mold. Before measurement, the cell was charged at a constant voltage for 4 hours at 50°C to eliminate the CO2 effect. The ohmic impedance of the membrane was recorded under a fully humidified N2 environment at different temperatures (30 to 80°C in 10°C increments) in a fuel cell test station.

[0116] (4) Intrinsic viscosity

[0117] The intrinsic viscosity of branched polymers was measured using an Ubbelohde viscometer in a DMSO solution at 25°C. First, the target sample was dissolved in DMSO to form a 3 mg mL -1 The polymer solution was then automatically diluted in sequence to five concentrations (3.0, 2.5, 2.0, 1.5, and 1.0 mg mL -1 ) and record the outflow time five times.

[0118] (5) Tensile strength

[0119] (6) Elongation at break

[0120] AEM samples were cut into dumbbell shapes (1 x 5 cm) using a specialized film cutter. The AEM samples were then secured in the slots of a tensile testing machine. The tensile strength and elongation at break of the AEM were measured at room temperature. The tensile speed was 10 mm / min.

[0121] The products obtained in Examples 1-2 were subjected to performance tests, and the performance is shown in Table 1 below:

[0122] Table 1 Performance test results

[0123]

[0124] The stress-strain curves of the anion exchange membranes prepared in Examples 1-2 and Comparative Example 1 are as follows: Figure 4 As shown; the ionic conductivity of the anion exchange membrane prepared in Example 1-2 and Comparative Example 1 at different temperatures is as shown Figure 5 shown.

[0125] (7) Electrolyzer test

[0126] The anode used uncatalyzed nickel felt, and the cathode used carbon paper loaded with a Pt / C catalyst. The anode and cathode, along with the membrane, were placed in a custom-made anion exchange membrane electrolyzer. Testing was performed using a Blue Electric test system.

[0127] The electrochemical performance of oxygen evolution of the anion exchange membrane prepared in Example 1 in the electrolyzer (AEMWEs) is as follows: Figure 6 、 Figure 10 As shown; long-term stability tests are as follows Figure 7 、 Figure 11 shown.

[0128] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A branched polyarylpiperidine polymer having the following structural formula: in, include Ar1-1 is One or more of the following; Ar1-2 is Ar2 is and / or 2. The method for preparing a branched polyarylpiperidine polymer according to claim 1, wherein In the structural formula, the molar ratio of Ar1-1, Ar2, and Ar1-2 is 12-18:0.4-2:2-8.

3. A method for preparing a branched polyarylpiperidine polymer according to claim 1, characterized in that: The steps include: S1, dissolving a linear phenyl monomer, a branched phenyl monomer, 1,2-diphenylethane and N-methyl-4-piperidone in an organic solvent 1, and stirring and mixing to obtain a precursor polymer solution; adding trifluoroacetic acid and trifluoromethanesulfonic acid dropwise to the precursor polymer solution, stirring and reacting, and obtaining a precipitate as a branched polyaromatic piperidine polymer precursor; S2. Dissolving the branched polyaromatic piperidine polymer precursor in organic solvent 2, adding methyl iodide and potassium carbonate, and stirring to react. The resulting precipitate is the quaternized branched polyaromatic piperidine polymer.

4. The method for preparing a branched polyarylpiperidine polymer according to claim 3, wherein In step S1, the linear structure phenyl monomer includes one or more of biphenyl, p-terphenyl, and fluorene; And / or, the branched structure phenyl monomer includes one or more of 9,9-diphenylfluorene and 9-phenylcarbazole.

5. The method for preparing a branched polyarylpiperidine polymer according to claim 3, wherein: In step S1, the molar ratio of the linear phenyl monomer, the branched phenyl monomer, and 1,2-diphenylethane is 12-18:0.4-2:2-8; and / or, the molar ratio of the linear phenyl monomer to N-methyl-4-piperidone is 22-26:32-36; And / or, the usage ratio of the linear phenyl monomer, N-methyl-4-piperidone, and the organic solvent 1 is 22-26 mmol: 32-36 mmol: 20-30 ml; And / or, the volume ratio of trifluoroacetic acid, trifluoromethanesulfonic acid and organic solvent 1 is 3-4:20-30:20-30.

6. The method for preparing a branched polyarylpiperidine polymer according to claim 3, wherein: In step S1, the stirring and mixing temperature is -5 to -2°C and the time is 10 to 40 minutes.

7. The method for preparing a branched polyarylpiperidine polymer according to claim 3, wherein: In step S2, the usage ratio of the branched polyaromatic piperidine polymer precursor, methyl iodide, and potassium carbonate is 1 g: 1.5-2.5 ml: 1.5-2.5 g.

8. Use of the branched polyarylpiperidine polymer according to claim 1 in preparing anion exchange membrane.

9. A method for preparing an anion exchange membrane, comprising the following steps: The branched polyaromatic piperidine polymer according to claim 1 is dissolved in an organic solvent 2, the filtered polymer solution is spread on a carrier, and dried to obtain 1 - Type membrane; - The membrane is peeled off and soaked in alkaline solution to obtain an anion exchange membrane.

10. The method for preparing an anion exchange membrane according to claim 9, characterized in that: The usage ratio of the branched polyaromatic piperidine polymer and the organic solvent 2 is 0.2 g: 3-8 ml; and / or, drying is performed at 70 to 90° C. for 20 to 30 hours; And / or, the obtained I - The thickness of the mold film is 10 to 30 μm; And / or, the soaking temperature is ∼65° C. and the soaking time is 10 to 15 hours.

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