Polyaromatic amphoteric polymer, preparation method thereof and ion exchange membrane

Abstract

The invention provides a polyaromatic amphoteric polymer, a preparation method thereof and an ion exchange membrane. The polyaromatic amphoteric polymer is composed of a polyaromatic main chain, a long side chain quaternary ammonium salt structure with positive charges and a sulfonate radical structure with long side chains with negative charges. The structure of the polyaromatic amphoteric polymer is shown as a formula 1: # imgabs0 #. The invention also provides a preparation method of the polyaromatic amphoteric polymer and an ion exchange membrane prepared from the polyaromatic amphoteric polymer. The ion exchange membrane has high ionic conductivity, mechanical strength and stability.

Description

Technical Field

[0001] The present invention relates to a polyaromatic amphoteric polymer, a preparation method thereof, and an ion exchange membrane, belonging to the field of preparation of polymer materials. Background Art

[0002] With the gradual increase in social requirements for low-carbon environmental protection in recent years, new green and clean energy technologies such as hydrogen production by electrolyzing water, fuel cells, and energy storage batteries have become research hotspots. Among them, the ion exchange membrane, as a core component widely used in devices such as fuel cells, hydrogen production by electrolyzing water, and flow batteries, its performance directly affects the performance of the overall device. Currently, one of the commercially mature ion exchange membranes is the perfluorosulfonic acid membrane, which has advantages such as high ion conductivity and good chemical stability. However, due to its high price, it limits a more extensive commercialization process. Therefore, many types of ion exchange polymers have been developed by researchers. Among them, polymers with a polyaromatic backbone (Adv. Funct. Mater. 2017, 1702758) have higher stability compared to traditional polyethers or polysulfones because their main chain does not contain electron-withdrawing ether or sulfone bonds. However, due to the different application fields of ion exchange membranes, the structure needs to be reasonably and precisely regulated to meet different requirements.

[0003] CN113817197A discloses an amphoteric polyether ether ketone ion exchange membrane and a preparation method thereof. The main chain structure of this polyether ether ketone contains aryl ether bonds, which is not conducive to the long-term stability of the polymer. At the same time, its ionic groups are close to the polymer main chain, which will more easily attract free radicals to approach, making the main chain vulnerable to free radical attack. At the same time, the structure with ionic groups close to the main chain makes the free volume of the polymer smaller, and its stability and ion transport ability need to be further improved.

[0004] CN115819734A discloses an anion exchange membrane with an amphoteric ionic side chain structure. This anion exchange membrane is an anion exchange membrane prepared by introducing a negatively charged group on the positively charged side chain. However, in this method, the quaternary ammonium positive charge is close to the main chain, attacking the main chain, which is not conducive to the stability of the main chain. Secondly, the presence of negatively charged sulfonate groups in this membrane must rely on positively charged groups. The positive and negative charge side chains are interdependent and have the same content, and are not independent of each other. The content of a certain type of charge cannot be controlled alone. Therefore, the performance of the polymer cannot be precisely regulated.

[0005] CN109880138A and CN112898539A respectively disclose a polyindigoarene with a long side chain ammonium salt and its anion exchange membrane. The lactam structure connecting the functional group side chain in the main chain of this polyindigoarene will undergo hydrolysis and ring opening in an aqueous solution, which is not conducive to the stability of the main chain and the lifespan of the membrane.

[0006] In summary, although the current ion exchange membranes have good ionic conductivity, their stability, mechanical strength, and comprehensive performance still need to be further improved. It is necessary to develop an ion exchange membrane that combines high ionic conductivity, high mechanical strength, and high stability to meet the application requirements in different fields. Summary of the Invention

[0007] To solve the above technical problems, the purpose of the present invention is to provide a polyaromatic amphoteric polymer and a preparation method thereof. Using this polyaromatic amphoteric polymer to prepare an ion exchange membrane can improve the ionic conductivity, chemical stability, and mechanical properties of the ion exchange membrane.

[0008] To achieve the above purpose, the present invention provides a polyaromatic amphoteric polymer, wherein the polyaromatic amphoteric polymer is composed of a polyaromatic main chain, a long side chain quaternary ammonium salt structure with a positive charge, and a sulfonate structure of a long side chain with a negative charge;

[0009] The structure of the polyaromatic amphoteric polymer is shown in Formula 1:

[0010]

[0011] In Formula 1, x, y, and z are the molar ratios of each block, and 0 < x < 1, 0 < y < 1, 0 ≤ z < 1, x + y + z = 1; n is 1 - 8, m is 1 - 8, M is a ketone-containing monomer structure, and Ar is an aromatic monomer structure.

[0012] In the above polyaromatic amphoteric polymer, preferably, the quaternary ammonium salt side chain structure is selected from the cyclic quaternary ammonium salt shown in Formula 2 or the alkyl quaternary ammonium salt shown in Formula 3:

[0013]

[0014] In the above polyaromatic amphoteric polymer, preferably, the polyaromatic main chain structure is obtained by reacting carbazole and a ketone-containing monomer, and preferably further contains an aromatic monomer, that is, the polyaromatic main chain structure can be composed of carbazole and a ketone-containing monomer structure, or composed of carbazole, a ketone-containing monomer structure, and an aromatic monomer structure.

[0015] In the above polyaromatic amphoteric polymer, preferably, the ketone-containing monomer is selected from one or a combination of two or more of the following structures:

[0016]

[0017] In the above polyaromatic amphoteric polymer, preferably, the aromatic monomer is selected from one or a combination of two or more of the following structures:

[0018]

[0019] Among them, R 1- R 6 Each independently selected from hydrogen, fluorine, methyl or ethyl.

[0020] In the above polyaromatic amphoteric polymer, preferably, the value of x is 0.1 - 0.9, the value of y is 0.1 - 0.8, the value of z is 0 - 0.1, and n is an integer from 1 to 3.

[0021] In the above polyaromatic amphoteric polymer, preferably, the polyaromatic amphoteric polymer is one of the following polymers:

[0022]

[0023]

[0024] The present invention also provides a preparation method of the above polyaromatic amphoteric polymer, which includes the following steps:

[0025] Dissolve carbazole, a ketone-containing monomer and an aromatic monomer in solvent A, and carry out a polymerization reaction under the catalysis of catalyst S. After the reaction is completed, pour the product into solvent B to precipitate the polyaromatic main chain; wherein, the molar ratio of the carbazole, the aromatic monomer and the ketone-containing monomer is 1:0 - 0.5:(1 - 1.5);

[0026] After dissolving the polyaromatic main chain in solvent C, add a sulfonating reagent and a quaternizing reagent, and react the mixed solution at 20 - 80°C. After the reaction is completed, pour the mixed solution into water and filter to obtain the polyaromatic amphoteric polymer.

[0027] In the above preparation method, preferably, the catalyst S is one or a combination of two or more of methanesulfonic acid, trifluoromethanesulfonic acid, and trifluoroacetic acid.

[0028] In the above preparation method, preferably, the molar ratio of the catalyst S to the ketone-containing monomer is 1:(1 - 20).

[0029] In the above preparation method, preferably, the solvent A is one or a combination of two or more of dichloromethane, chloroform, and toluene.

[0030] In the above preparation method, preferably, the temperature of the reaction is -10°C to 35°C, such as -10°C, 0°C, 20°C, etc.

[0031] In the above preparation method, preferably, the reaction time is 1 - 24 h, such as 1 h, 10 h, 24 h, etc.

[0032] In the above preparation method, preferably, the solvent B is one or a combination of two or more of water, methanol, and ethanol.

[0033] In the above preparation method, preferably, the quaternization reagent is a halogenated trimethylammonium salt, a halogenated methylpiperidinium salt or a halogenated methylpyrrolidinium salt with a carbon chain length of 3-10.

[0034] In the above preparation method, preferably, the sulfonation reagent is a halogenated sulfonate X-(CH 2 )y 2 -SO 3 M, where X represents a halogen and y 2 represents the carbon chain length.

[0035] In the above preparation method, the ratio of the sulfonation reagent to the quaternization reagent can be arbitrary.

[0036] In the above preparation method, preferably, the solvent C is one or a combination of two or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0037] The present invention also provides an ion exchange membrane prepared using the above polyaromatic amphoteric polymer.

[0038] According to a specific embodiment of the present invention, preferably, the process for preparing the ion exchange membrane using the above polyaromatic amphoteric polymer includes the following steps:

[0039] Dissolve the polyaromatic amphoteric polymer in solvent D to obtain a casting solution, coat the casting solution on the surface of a substrate, and then dry it to obtain the ion exchange membrane.

[0040] According to a specific embodiment of the present invention, preferably, the mass fraction of the casting solution is 1%-30%.

[0041] According to a specific embodiment of the present invention, preferably, the drying conditions are drying at 60-90°C for 6-24 h.

[0042] According to a specific embodiment of the present invention, preferably, the solvent D is one or a combination of two or more of N’,N’-dimethylformamide, N’,N’-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, n-propanol, isopropanol, ethylene glycol, glycerol, n-butanol, isobutanol, or water.

[0043] According to a specific embodiment of the present invention, preferably, the substrate is a glass plate.

[0044] The ion exchange membrane provided by the present invention can be used in fields such as fuel cells, hydrogen production by electrolysis of water, and flow batteries.

[0045] The technical solution of the present invention has the following technical effects:

[0046] (1) The functional groups of the polyaromatic amphoteric polymer of the present invention are composed of two independent long side chain units with opposite charges, and the contents of anionic and cationic groups can be controlled separately, realizing precise regulation of membrane performance; among them, the long side chains make the polymer segments more likely to entangle, and at the same time, the strong electrostatic interaction between positive and negative charges forms an ionic cross-linked structure, improving the mechanical strength of the polymer.

[0047] (2) The main chain of the polyaromatic amphoteric polymer of the present invention is composed of polyaromatic groups without ether bonds, and there are no ionic groups or lactam structures prone to hydrolysis near the main chain. The ionic groups are far from the main chain, making the main chain less vulnerable to radical attacks and having stronger chemical stability.

[0048] (3) The long side chain structure of the polyaromatic amphoteric polymer of the present invention gives the polymer a larger free volume, improves the degree of hydration of the polymer, and enhances the ionic conductivity. It can be used as a separator for fuel cells, water electrolysis or flow batteries. When used as a separator for flow batteries, due to the Donnan effect, the vanadium ion permeability can be reduced. Description of the Drawings

[0049] Figure 1 It is the NMR chart of the polymer main chain of Example 1.

[0050] Figure 2 It is the physical picture of the ion exchange membrane of Example 1. Detailed Embodiments

[0051] For a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will be described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0052] Example 1

[0053] This example provides a polyaromatic amphoteric polymer, which is prepared by the following steps:

[0054] Add 1 g of carbazole and 0.57 g of 2,3-butanedione into a dry flask, and then add 20 mL of dichloromethane to dissolve; add 9.2 mL of trifluoroacetic acid to the solution at 0 °C to obtain a mixed solution; after the mixed solution is stirred at room temperature for 12 h, pour it into a mixed solution of ethanol and water to precipitate, and wash with water to obtain the polymer main chain. The NMR chart of this polymer main chain is as Figure 1 shown.

[0055] Dissolve 1 g of the polymer main chain in 25 mL of N’,N’-dimethylformamide, add 0.97 g of sodium 5-bromopentanesulfonate and 0.12 g of (5-bromopentyl)trimethylammonium bromide. React the reaction system at 80 °C for 36 h. Pour the product into an aqueous solution to precipitate, and wash and filter with deionized water to obtain the polyaromatic amphoteric polymer, whose structure is shown below:

[0056]

[0057] Dissolve the obtained polyaromatic amphoteric polymer in dimethyl sulfoxide to obtain a casting solution with a concentration of 10 wt.%. Coat the casting solution on a glass substrate and dry it at 85 °C for 12 hours to obtain an ion exchange membrane, as Figure 2 shown.

[0058] Example 2

[0059] This example provides a polyaromatic amphoteric polymer, which is prepared by the following steps:

[0060] Add 1 g of carbazole, 0.5 g of 2,3-butanedione and 0.1 g of biphenyl into a dry flask, then add 20 mL of dichloromethane to dissolve. Add 9.2 mL of trifluoroacetic acid to the solution at 0 °C to obtain a mixed solution. After stirring and reacting the mixed solution at room temperature for 12 h, pour it into a mixed solution of ethanol and water to precipitate and wash with water to obtain the polymer main chain.

[0061] Dissolve 1 g of the polymer main chain in 25 mL of N’,N’-dimethylformamide, add 0.83 g of sodium 5-bromopentanesulfonate and 0.09 g of (5-bromopentyl)trimethylammonium bromide. React the reaction system at 80 °C for 36 h. Pour the product into an aqueous solution to precipitate, and wash and filter with deionized water to obtain the polyaromatic amphoteric polymer, whose structure is shown below:

[0062]

[0063] Dissolve the obtained polyaromatic amphoteric polymer in dimethyl sulfoxide to obtain a casting solution with a concentration of 10 wt.%. Coat the casting solution on a glass substrate and dry it to obtain an ion exchange membrane.

[0064] Example 3

[0065] This example provides a polyaromatic amphoteric polymer, which is prepared by the following steps:

[0066] Add 2 g of carbazole, 0.24 g of bibenzyl, and 2.31 g of 2,2,2-trifluoroacetophenone to a dry flask, then add 20 mL of dichloromethane to dissolve. Add 15 mL of trifluoroacetic acid and 16 mL of trifluoromethanesulfonic acid to the solution at 0 °C to obtain a mixed solution. After stirring and reacting the mixed solution at room temperature for 8 h, pour it into methanol to precipitate, and wash with methanol and water to obtain the polymer backbone.

[0067] Dissolve 2 g of the polymer backbone in 50 mL of N-methylpyrrolidone, and add 1.13 g of 3-bromopropylsulfonate sodium and 0.15 g of 3-bromopropyltrimethylammonium bromide. React the reaction system at 80 °C for 24 h. Pour the product into an aqueous solution to precipitate, and wash and filter with deionized water to obtain the polyaromatic amphoteric polymer, and its structure is as follows:

[0068]

[0069] Dissolve the obtained polyaromatic amphoteric polymer in dimethyl sulfoxide to obtain a casting solution with a concentration of 10 wt.%, and coat and dry the casting solution on a glass substrate to obtain an ion exchange membrane.

[0070] Example 4

[0071] The difference between this example and Example 3 is that 1.13 g of 3-bromopropylsulfonate sodium and 0.15 g of 3-bromopropyltrimethylammonium bromide are replaced with 1.23 g of 5-bromopentylsulfonate sodium and 0.18 g of 5-bromopentyltrimethylammonium bromide, and other conditions are exactly the same as those in Example 3. The obtained polyaromatic amphoteric polymer, and its structure is as follows:

[0072]

[0073] Example 5

[0074] This example provides a polyaromatic amphoteric polymer, which is prepared by the following steps:

[0075] Add 1 g of carbazole and 0.75 g of 3,4-hexanedione to a dry flask, then add 20 mL of dichloromethane to dissolve. Add 9.2 mL of trifluoroacetic acid to the solution at 0 °C to obtain a mixed solution. After stirring and reacting the mixed solution at room temperature for 12 h, pour it into a mixed solution of ethanol and water to precipitate, and wash with water to obtain the polymer backbone.

[0076] Dissolve 1 g of the polymer main chain in 25 mL of N’,N’-dimethylformamide, add 0.86 g of sodium 5-bromopentanesulfonate and 0.13 g of 1-(5-bromopentyl)-1-methylpiperidinium bromide, and react the reaction system at 80 °C for 36 h. Pour the product into an aqueous solution to precipitate, and wash and filter with deionized water to obtain a polyaromatic amphoteric polymer, the structure of which is shown below:

[0077]

[0078] Dissolve the obtained polyaromatic amphoteric polymer in dimethyl sulfoxide to obtain a casting solution with a concentration of 10 wt.%, and coat and dry the casting solution on a glass substrate to obtain an ion exchange membrane.

[0079] Comparative Example

[0080] The difference between the comparative example and Example 1 is that 0.97 g of sodium 5-bromopentanesulfonate and 0.12 g of (5-bromopentyl)trimethylammonium bromide are replaced with 1.08 g of sodium 5-bromopentanesulfonate, and other conditions are exactly the same as those in Example 1.

[0081] Testing method:

[0082] 1. Detect the ion conductivity of the ion exchange membranes obtained in the examples and comparative examples according to the following method, and the results are shown in Table 1.

[0083] Detection method: Use the alternating current impedance method to test with a two-electrode on an electrochemical workstation, and the test frequency is 100 Hz - 1 MHz; the test is carried out under the conditions of 80 °C and 100% relative humidity.

[0084] 2. Use a universal material testing machine to test the mechanical strength performance.

[0085] 3. Water absorption test method: Weigh the weight of the membrane in the dry state to obtain W_dry. Take out the membrane after soaking it in deionized water for 24 h, quickly blot the surface water droplets with filter paper, and weigh to obtain the wet weight W_wet. Repeat the process three times. The water absorption rate of the membrane = (W_wet - W_dry) / W_dry × 100%.

[0086] 4. Dimensional stability: Dry the membrane at 80 °C for 12 hours, measure the length and width of the membrane, and then soak the membrane in deionized water at 60 °C for 2 h, and measure the length and width L after water absorption. The swelling degree of the membrane = (L 吸水后 -L 吸水前 ) / L 吸水前 × 100%.

[0087] Table 1 Performance comparison between examples and comparative examples

[0088]

[0089]

[0090] It can be seen from the experimental results recorded in Table 1 that the ion exchange membranes prepared in Examples 1-5 have high ion conductivity, mechanical strength and dimensional stability.

Claims

1. A polyaromatic amphoteric polymer, wherein, the polyaromatic amphoteric polymer is composed of a polyaromatic main chain, a long side chain quaternary ammonium salt structure with a positive charge, and a sulfonate structure of a long side chain with a negative charge; the structure of the polyaromatic amphoteric polymer is shown in Formula 1: In Formula 1, x, y, and z are the molar ratios of each block, and 0 < x < 1, 0 < y < 1, 0 ≤ z < 1, x + y + z = 1; n is 1 - 8, m is 1 - 8, M is a ketone-containing monomer structure, and Ar is an aromatic monomer structure.

2. The polyaromatic amphoteric polymer according to claim 1, wherein, the quaternary ammonium salt side chain structure is selected from the cyclic quaternary ammonium salt shown in Formula 2 or the alkyl quaternary ammonium salt shown in Formula 3:

3. The polyaromatic amphoteric polymer according to claim 1, wherein, the polyaromatic main chain structure is obtained by reacting carbazole and a ketone-containing monomer, and preferably further contains an aromatic monomer.

4. The polyaromatic amphoteric polymer according to claim 3, wherein, the ketone-containing monomer is selected from one or a combination of two or more of the following structures:

5. The polyaromatic amphoteric polymer according to claim 3, wherein, the aromatic monomer is selected from one or a combination of two or more of the following structures: wherein, R 1 -R 6 each independently selected from hydrogen, fluorine, methyl or ethyl.

6. The polyaromatic amphoteric polymer according to claim 1, wherein, the value of x is 0.1 - 0.9, the value of y is 0.1 - 0.8, the value of z is 0 - 0.1, and n is an integer from 1 to 3.

7. The polyaromatic amphoteric polymer according to claim 1, wherein, the polyaromatic amphoteric polymer is one of the following polymers:

8. A preparation method of the polyaromatic amphoteric polymer according to any one of claims 1 - 7, which comprises the following steps: Dissolve carbazole, a ketone-containing monomer, and an aromatic monomer in solvent A, and carry out a polymerization reaction under the catalysis of catalyst S. After the reaction, pour the product into solvent B to precipitate the polyaromatic main chain; wherein, the molar ratio of carbazole, the aromatic monomer, and the ketone-containing monomer is 1:0 - 0.5:(1 - 1.5); After dissolving the polyaromatic main chain in solvent C, add a sulfonation reagent and a quaternization reagent, and react the mixed solution at 20 - 80 °C. After the reaction, pour the mixed solution into water and filter to obtain the polyaromatic amphoteric polymer.

9. The preparation method according to claim 8, wherein, the catalyst S is one or a combination of two or more of methanesulfonic acid, trifluoromethanesulfonic acid, and trifluoroacetic acid; the molar ratio of the catalyst S to the ketone-containing monomer is 1:(1 - 20); the solvent A is one or a combination of two or more of dichloromethane, chloroform, and toluene; the temperature of the reaction is -10 °C to 35 °C, and the time of the reaction is 1 - 24 h; the solvent B is one or a combination of two or more of water, methanol, and ethanol.

10. The preparation method according to claim 8, wherein, the quaternization reagent is a halogenated trimethylammonium salt, a halogenated methylpiperidinium salt, or a halogenated methylpyrrolidinium salt with a carbon chain length of 3 - 10; The sulfonation reagent is a halogenated sulfonate X-(CH 2 )y 2 -SO 3 M, where X represents a halogen and y 2 represents the carbon chain length; The solvent C is one or a combination of two or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

11. An ion exchange membrane, which is prepared from the polyaromatic amphoteric polymer according to any one of claims 1-7; Preferably, the preparation process comprises the following steps: Dissolve the polyaromatic amphoteric polymer in solvent D to obtain a casting solution, coat the casting solution on the surface of a substrate, and then dry it to obtain the ion exchange membrane; Preferably, the solvent D is one or a combination of two or more of N',N'-dimethylformamide, N',N'-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, n-propanol, isopropanol, ethylene glycol, glycerol, n-butanol, isobutanol, or water.

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