Ternary block polybenzimidazole and preparation method thereof

Abstract

The invention discloses ternary block polybenzimidazole and a preparation method thereof, and particularly discloses ternary block polybenzimidazole which is obtained by copolymerization of quaternary amine and two different types of carboxylic acid monomers. The prepared ternary block polybenzimidazole has a flexible PBI fragment (which is beneficial to ion conduction) and a rigid PBI fragment (which is good in mechanical property and chemical stability). Different fragments have different physical and chemical properties, and a phase separation structure forms a nano channel to construct an ion transmission channel. According to the preparation method disclosed by the invention, after the viscous solution is prepared by the polycondensation reaction, the ternary block polybenzimidazole primary pulp is prepared by the electrochemical reduction reaction, and unreacted monomers in the polycondensation reaction and oligomers generated by the polycondensation reaction can be reacted by the electrochemical reduction reaction; therefore, the yield of the ternary block polybenzimidazole is improved, the molecular weight distribution of the polybenzimidazole is reduced, and the molecular weight of the ternary block polybenzimidazole is improved.

Description

Technical Field

[0001] The invention relates to the field of block copolymers, and in particular to a ternary block polybenzimidazole and a preparation method thereof. Background Art

[0002] Polybenzimidazole (PBI) has good thermal stability, mechanical strength and flame retardant properties, and can be used in high temperature resistant fabrics, fire retardant materials, ion conduction membranes, etc.

[0003] As an ion-conducting membrane, it can be used in high-temperature fuel cells, water electrolysis to produce hydrogen and its CO2 conversion. However, PBI ion-conducting membranes have problems such as low ion conductivity and poor alkali stability in practical applications. The existing technology mainly introduces ionic groups into polybenzimidazole to increase the density of ionic groups in the membrane, form efficient ion transmission channels, and obtain ion exchange membranes with higher ion exchange capacity. However, this method will increase the water absorption and swelling rate of the membrane and reduce the dimensional stability and mechanical properties of the membrane.

[0004] Block copolymerization is a method of designing and modifying the main chain of molecules and is often used in the modification of new polymer materials. It can bring out the advantages of each polymer in the block copolymer and effectively improve the various properties of the polymer. The different physical and chemical properties of different blocks of the block copolymer can form a nanophase separation structure in the membrane, thereby forming a continuous ion nanochannel, which is conducive to the transmission of ions.

[0005] ZL202010990281.5 discloses a polybenzimidazole-polysiloxane block copolymer and its preparation method and application. PBI and PDMS can form a chemical bond to improve the compatibility of the two. The formed block copolymer has amphiphilicity, forming a soft-hard, affinity-repellency phase separation structure, promoting the formation of proton transmission channels.

[0006] 202310179941.5 discloses a ternary block copolymer polybenzimidazole, a high-temperature proton exchange membrane and a preparation method thereof, using an OPBI prepolymer with a carboxyl terminal group, an F6-PBI prepolymer with a carboxyl terminal group and an m-PBI prepolymer with a diamino terminal group for polymerization reaction, and the obtained ternary block copolymer has easy solubility, high film-forming property, high thermal stability, high oxidation resistance, etc.

[0007] Both block polybenzimidazole copolymers can undergo phase separation in microstructure, effectively promoting proton conduction and phosphoric acid retention. However, neither of them mentions the molecular weight control of the copolymers. Summary of the invention

[0008] In order to overcome the shortcomings of the prior art, the present invention provides a ternary block polybenzimidazole, which is obtained by copolymerizing a tetraamine and two different types of carboxylic acid monomers. The prepared ternary block polybenzimidazole has a flexible PBI segment (conducive to ion conduction) and a rigid PBI segment (good mechanical properties and chemical stability). Different segments have different physical and chemical properties, and the phase separation structure forms a nanochannel to construct an ion transmission channel.

[0009] Another object of the present invention is to provide a method for preparing a ternary block polybenzimidazole, comprising the following steps: S1: adding a protic solvent and a quaternary amine into a three-necked flask equipped with a reflux condenser, introducing an inert gas, heating, and stirring to dissolve the quaternary amine; S2: adding dicarboxylic acid A to step S1, heating to T1 and reacting; S3: Cool down to T2, add dicarboxylic acid B into step S2, wait for dicarboxylic acid B to dissolve, heat up to T3 to start prepolymerization, and then heat up to T4 to start polycondensation to obtain a viscous solution; S4: subjecting the viscous solution in step S3 to an electrochemical reduction reaction to obtain a ternary block polybenzimidazole stock paste; S5: pouring the ternary block polybenzimidazole slurry in step S4 into deionized water, and then washing with alkali solution and deionized water in sequence, and drying to obtain the product.

[0010] According to the present invention, the protic solvent in step S1 is polyphosphoric acid or Eaton's reagent.

[0011] Furthermore, the Eaton reagent is a mixture of phosphorus pentoxide and methanesulfonic acid.

[0012] Furthermore, the weight ratio of methanesulfonic acid to phosphorus pentoxide in the mixed reagent is 1:0.1-0.125.

[0013] According to the present invention, the structural formula of the tetraamine in step S1 is .

[0014] Further, the R1 represents: , , , or .

[0015] Further, the R2 represents: O, -CH2, C=O or CH(CH3) 2。

[0016] According to the present invention, the weight ratio of the protic solvent to the tetraamine in step S1 is 1:(0.01-0.1).

[0017] According to the present invention, the inert gas in step S1 is nitrogen, argon or helium.

[0018] According to the present invention, the heating temperature in step S1 is 40-80° C., and the stirring time is 2-4 hours.

[0019] According to the present invention, the dicarboxylic acid A in step S2 contains non-polar functional groups other than carboxyl groups.

[0020] According to the present invention, the dicarboxylic acid A in step S2 includes but is not limited to and .

[0021] Furthermore, the R3 represents: CF3-C-CF3 or CF2-C-CH3.

[0022] According to the present invention, the molar ratio of the dicarboxylic acid A in step S2 to the tetraamine in step S1 is 1:0.1-0.9.

[0023] According to the present invention, the temperature T1 in step S2 is 100-120°C.

[0024] According to the present invention, the reaction time in step S2 is 3 to 6 hours.

[0025] According to the present invention, the temperature T2 in step S3 is 70-90°C.

[0026] According to the present invention, the structural formula of the dicarboxylic acid B in step S3 is: , , , , or .

[0027] According to the present invention, the molar ratio of the dicarboxylic acid B in step S3 to the dicarboxylic acid A in step S2 is 1:1-9.

[0028] According to the present invention, the temperature T3 in step S3 is 90-110°C.

[0029] According to the present invention, the prepolymerization time in step S3 is 1 to 3 hours.

[0030] According to the present invention, the temperature T4 in step S3 is 140-160°C.

[0031] According to the present invention, the polycondensation reaction time in step S3 is 2 to 24 hours.

[0032] According to the present invention, the current of the electrochemical reduction reaction in step S4 is 0.01 to 1 A, and the time is 1 to 60 minutes.

[0033] According to the present invention, the alkali solution in step S5 is a sodium bicarbonate aqueous solution, a sodium carbonate aqueous solution, a potassium bicarbonate aqueous solution or a potassium carbonate aqueous solution.

[0034] According to the present invention, the weight concentration of the alkali solution in step S5 is 5-40%.

[0035] According to the present invention, the conditions for washing with alkaline solution in step S5 are: room temperature to 80° C., 1 to 24 hours.

[0036] According to the present invention, the number of times of washing with deionized water in step S5 is 3 to 10 times.

[0037] According to the present invention, the drying temperature in step S5 is 60-100° C., and the drying time is 5-24 hours.

[0038] Another object of the present invention is to provide a ternary block polybenzimidazole for use in high temperature resistant fabrics, fire retardant materials, ion conducting membranes, etc. Compared with the prior art, the present invention has the following advantages:

[0039] 1) The present invention uses tetraamine and two different types of dicarboxylic acids as monomers to obtain ternary block polybenzimidazole through polycondensation. The obtained block polybenzimidazole contains a flexible hydrophilic PBI segment (which is conducive to ion conduction) and a rigid PBI segment (which has good mechanical properties and chemical stability). The two segments have different physical and chemical properties. The obtained copolymer membrane can form nanochannels, greatly improving the ion conductivity.

[0040] 2) The present invention uses an electrochemical reduction reaction to obtain a ternary block polybenzimidazole stock after a viscous solution is obtained by a polycondensation reaction. The electrochemical reduction reaction can cause unreacted monomers in the polycondensation reaction and oligomers produced by the polycondensation reaction to react, thereby increasing the yield of the ternary block polybenzimidazole and reducing the molecular weight distribution of the polybenzimidazole, thereby increasing the molecular weight of the ternary block polybenzimidazole. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the infrared spectrum of the ternary block polybenzimidazole prepared in Example 1 of the present invention; Figure 2 This is the infrared spectrum of the ternary block polybenzimidazole prepared in Example 2 of the present invention; Figure 3 This is the infrared spectrum of the ternary block polybenzimidazole prepared in Example 3 of the present invention; Figure 4This is the infrared spectrum of the ternary block polybenzimidazole prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0042] A method for preparing a ternary block polybenzimidazole comprises the following steps: S1: adding a protic solvent and a quaternary amine into a three-necked flask equipped with a reflux condenser, introducing an inert gas, heating, and stirring to dissolve the quaternary amine; S2: adding dicarboxylic acid A to step S1, heating to T1 and reacting; S3: Cool down to T2, add dicarboxylic acid B into step S2, wait for dicarboxylic acid B to dissolve, heat up to T3 to start prepolymerization, and then heat up to T4 to start polycondensation to obtain a viscous solution; S4: subjecting the viscous solution in step S3 to an electrochemical reduction reaction to obtain a ternary block polybenzimidazole stock paste; S5: pouring the ternary block polybenzimidazole slurry in step S4 into deionized water, and then washing with alkali solution and deionized water in sequence, and drying to obtain the product.

[0043] According to the present invention, the polycondensation reaction time in step S3 is 2 to 24 hours.

[0044] Furthermore, the polycondensation reaction time is 4 to 12 hours.

[0045] The polycondensation reaction time affects the reaction degree of the ternary block copolymer and the molecular weight of the copolymer. When the reaction time is 4 to 12 hours, the obtained copolymer has good solubility and is easy to form a film.

[0046] According to the present invention, the current of the electrochemical reduction reaction in step S4 is 0.01 to 1 A, and the time is 1 to 60 minutes.

[0047] Furthermore, the current of the electrochemical reduction reaction is 0.1-0.5A, and the time is 5-30min.

[0048] Under the action of the electric field, the types and properties of unreacted monomers and oligomers in the viscous solution affect the effect of the electrochemical reduction reaction. When the current is 0.1-0.5A and the time is 5-30min, the yield of ternary block polybenzimidazole can be greatly improved, the molecular weight distribution of polybenzimidazole can be narrowed, and the molecular weight of ternary block polybenzimidazole can be increased.

[0049] Comparative Example 1 162 g MSA, 18 g P2O5 and 0.0264 mol 1,2,4,5-tetraaminobenzene were weighed and added to a three-necked flask equipped with a reflux condenser, argon was introduced, and the mixture was heated and stirred in an oil bath at 60 °C for 2 h; 0.00264 mol 2,2-bis(4-carboxyphenyl)hexafluoropropane was added to the above solution, stirred under argon protection, the temperature was raised to 100 °C and reacted for 4 h; the temperature was lowered to 70 °C, and 0.02376 mol Add terephthalic acid to the above solution, stir under argon protection, raise the temperature to 110°C for prepolymerization for 1 hour, then raise the temperature to 140°C for condensation reaction for 4 hours to obtain a viscous reaction solution; pour the solution into water for precipitation, soak the precipitate in 80°C, 5% sodium bicarbonate aqueous solution for 24 hours, then wash with deionized water 10 times, take out and dry at 80°C for 15 hours to obtain TB-PBI-1. The ternary block polybenzimidazole Mw = 412.05 KDa.

[0050] Example 1 162 g MSA, 18 g P2O5 and 0.0264 mol 1,2,4,5-tetraaminobenzene were weighed and added to a three-necked flask equipped with a reflux condenser, argon was introduced, and the mixture was heated and stirred in an oil bath at 60 °C for 2 h; 0.00264 mol 2,2-bis(4-carboxyphenyl)hexafluoropropane was added to the above solution, stirred under argon protection, the temperature was raised to 100 °C and reacted for 4 h; the temperature was lowered to 70 °C, and 0.02376 mol Add terephthalic acid to the above solution, stir under argon protection, raise the temperature to 110°C for prepolymerization for 1 hour, then raise the temperature to 140°C for condensation reaction for 4 hours to obtain a viscous reaction solution; electrochemically reduce the reaction solution (0.1A, 30 minutes) to obtain a ternary block polybenzimidazole solution; pour the solution into water for precipitation, soak the precipitate in 80°C, 5% sodium bicarbonate aqueous solution for 24 hours, then wash with deionized water 10 times, take out and dry at 80°C for 15 hours to obtain TB-PBI-1. The infrared spectrum of the synthetic product TB-PBI-1 is shown as follows Figure 1 As shown, at 1108 cm -1 The absorption peak at 927~969 cm- 1 and 1105~1274 cm -1 The broad peak is derived from the CF bond, which proves the synthesis of the ternary block polybenzimidazole. The ternary block polybenzimidazole has a Mw of 567.94 KDa.

[0051] Example 2 162 g MSA, 16.2 g P2O5 and 0.0264 mol 3,3-diaminobenzidine were weighed and added into a three-necked flask equipped with a reflux condenser, argon was introduced, and the mixture was heated and stirred in an oil bath at 50°C for 3 h; 0.00792 mol terephthalic acid was added to the above solution, stirred under argon protection, heated to 100°C and reacted for 6 h; when the temperature dropped to 80°C, 0.01848 mol 3,4'-dicarboxybiphenyl was added to the above solution, stirred under argon protection, heated to 100°C for prepolymerization reaction for 3 h, and then heated to 150°C for polycondensation reaction for 6 h to obtain a viscous reaction solution. The reaction solution was subjected to an electrochemical reduction reaction (0.3A, 15min) to obtain a ternary block polybenzimidazole stock paste; the stock paste was poured into water for precipitation, and then the precipitate was immersed in a 10% potassium bicarbonate aqueous solution at 60°C for 18h, then washed with deionized water for 8 times, and then taken out and dried at 100°C for 5h to obtain TB-PBI-2. The infrared spectrum of the synthetic product TB-PBI-2 is shown in Figure 2 As shown, at 1630 cm -1 The absorption peak at 700-900 cm- 1 The peak of is derived from the substitution of benzene ring, which proves the synthesis of ternary block polybenzimidazole. The ternary block polybenzimidazole has Mw = 729.97 KDa.

[0052] Example 3 162 g MSA, 18.2 g P2O5 and 0.0264 mol 1,2,6,7-phenyltetramine were weighed and added into a three-necked flask equipped with a reflux condenser, argon was introduced, and the mixture was heated and stirred in an oil bath at 40°C for 4 hours; 0.0132 mol terephthalic acid was added to the above solution, stirred under argon protection, heated to 120°C and reacted for 3 hours; when the temperature dropped to 90°C, 0.0132 mol 4,4-dicarboxydiphenyl ether was added, stirred under argon protection, the temperature was raised to 90°C for prepolymerization reaction for 3 hours, and the temperature was raised to 160°C for condensation reaction for 12 hours to obtain a viscous reaction solution. The reaction solution was subjected to an electrochemical reduction reaction (0.5A, 5min) to obtain a ternary block polybenzimidazole stock; the stock was poured into water for precipitation, and then the precipitate was immersed in a 20% potassium bicarbonate aqueous solution at 40°C for 24h, then washed with deionized water for 6 times, and dried at 60°C for 24h to obtain a block copolymer TB-PBI-3. The infrared spectrum of the synthetic product TB-PBI-3 is shown in Figure 3 As shown, at 1635 cm -1 The absorption peak at 880 cm- 1 , 800 cm -1 and 700 cm-1 The broad peak of is derived from the benzene ring substitution peak, which proves the synthesis of ternary block polybenzimidazole. The ternary block polybenzimidazole Mw = 1211.68 KDa.

[0053] Example 4 162 g MSA, 18 g P2O5 and 0.0264 mol 3,3,4,4-tetraaminodiphenyl ether were weighed and added into a three-necked flask equipped with a reflux condenser, argon was introduced, and the mixture was heated and stirred in an oil bath at 80°C for 2 h; 0.01848 mol 1,4-dicarboxycyclopentyl ether was added, and the mixture was stirred under argon protection, the temperature was raised to 120°C and reacted for 3 h; when the temperature dropped to 80°C, 0.00792 mol terephthalic acid was added to the above solution, and the mixture was stirred under argon protection, the temperature was raised to 100°C for prepolymerization reaction for 2 h, and then the temperature was raised to 150°C for condensation reaction for 10 h to obtain a viscous reaction solution. The reaction solution was subjected to an electrochemical reduction reaction (0.4A, 8min) to obtain a ternary block polybenzimidazole stock paste; the stock paste was poured into water for precipitation, and then the precipitate was immersed in a 40% sodium carbonate aqueous solution at room temperature for 24 hours, then washed with deionized water for 5 times, and then taken out and dried at 70°C for 12 hours to obtain TB-PBI-4. The infrared spectrum of the synthetic product TB-PBI-4 is shown in Figure 4 As shown, 2925 cm -1 and 2850cm -1 represents the presence of methylene; 1700 cm -1 The presence of an amide group without an imidazole ring; -1 The absorption peak at 1105~1274 cm belongs to the stretching vibration absorption peak of C=N, indicating the existence of imidazole ring; -1 The broad peak originates from the CO bond; 800 cm -1 The ternary block polybenzimidazole is synthesized with a Mw of 1007.44 KDa.

Claims

1. A method for preparing a ternary block polybenzimidazole, characterized in that: The following steps are involved: S1: adding a protic solvent and a quaternary amine into a three-necked flask equipped with a reflux condenser, introducing an inert gas, heating, and stirring to dissolve the quaternary amine; S2: adding dicarboxylic acid A to step S1, heating to T1 and reacting; S3: Cool down to T2, add dicarboxylic acid B into step S2, wait for dicarboxylic acid B to dissolve, heat up to T3 to start prepolymerization, and then heat up to T4 to start polycondensation to obtain a viscous solution; S4: subjecting the viscous solution in step S3 to an electrochemical reduction reaction to obtain a ternary block polybenzimidazole stock paste; S5: pouring the ternary block polybenzimidazole slurry in step S4 into deionized water, and then washing with alkali solution and deionized water in sequence, and drying to obtain the product.

2. The preparation method according to claim 1, characterized in that: In step S1, the protic solvent is polyphosphoric acid or Eaton's reagent; the Eaton's reagent is a mixture of phosphorus pentoxide and methane sulfonic acid; the weight ratio of methane sulfonic acid to phosphorus pentoxide in the mixed reagent is 1:0.1-0.

125.

3. The preparation method according to claim 1, characterized in that: The structural formula of the tetraamine in step S1 is ； Further, the R1 represents: , , , or ; Further, the R2 represents: O, -CH2, C=O or CH(CH3) 2。 4. The preparation method according to claim 1, characterized in that: The weight ratio of the protic solvent to the tetraamine in step S1 is 1:0.01-0.1; the inert gas in step S1 is nitrogen, argon or helium; the heating temperature in step S1 is 40-80° C., and the stirring time is 2-4 hours.

5. The preparation method according to claim 1, characterized in that: The dicarboxylic acid A in step S2 contains a non-polar functional group other than a carboxyl group; the dicarboxylic acid A is or ; Furthermore, the R3 represents: CF3-C-CF3 or CF2-C-CH3.

6. The preparation method according to claim 1, characterized in that: The molar ratio of the dicarboxylic acid A in step S2 to the tetraamine in step S1 is 1:0.1-0.9; T1 in step S2 is 100-120°C; the reaction time in step S2 is 3-6h; T2 in step S3 is 70-90°C.

7. The preparation method according to claim 1, characterized in that: The structural formula of the dicarboxylic acid B in step S3 is: , , , , or .

8. The preparation method according to claim 1, characterized in that: The molar ratio of the dicarboxylic acid B in step S3 to the dicarboxylic acid A in step S2 is 1:1-9; T3 in step S3 is 90-110°C; the prepolymerization time in step S3 is 1-3h; T4 in step S3 is 140-160°C; the polycondensation reaction time in step S3 is 2-24h; the current of the electrochemical reduction reaction in step S4 is 0.01-1A, and the time is 1-60min; the alkali solution in step S5 is a sodium bicarbonate aqueous solution, a sodium carbonate aqueous solution, a potassium bicarbonate aqueous solution or a potassium carbonate aqueous solution; the weight concentration of the alkali solution in step S5 is 5-40%; the conditions for alkali solution washing in step S5 are: room temperature-80°C, 1-24h; the number of deionized water washing in step S5 is 3-10 times; the drying temperature in step S5 is 60-100°C, and the drying time is 5-24h.

9. Ternary block polybenzimidazole prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the ternary block polybenzimidazole prepared by the preparation method according to any one of claims 1 to 8 in high temperature resistant fabrics, fire retardant materials and ion conducting membranes.

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