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CN-121362328-B - Block polybenzimidazole copolymer containing hydroxyl and sulfonic acid groups and preparation method and application of proton exchange membrane of block polybenzimidazole copolymer

CN121362328BCN 121362328 BCN121362328 BCN 121362328BCN-121362328-B

Abstract

The invention provides a segmented polybenzimidazole copolymer containing hydroxyl and sulfonic groups, a preparation method of a proton exchange membrane and application of the segmented polybenzimidazole copolymer. In the preparation process, a multiple hydrogen bond network is constructed by simultaneously introducing sulfonic acid groups and hydroxyl groups and imidazole rings, the conductivity is improved, the excessive swelling of the membrane in water is inhibited, a good microphase separation structure is formed in the membrane by utilizing a block structure to provide a continuous and efficient channel for proton transmission, and meanwhile, a series of rigid sulfonated diacid monomers with large steric hindrance are selected to weaken the intermolecular acting force, destroy the close-packed structure of a polymer main chain and improve the solubility of a high molecular weight polymer.

Inventors

  • XU ZHI
  • WANG YIXING
  • YU HAOWEI
  • WU YULIN

Assignees

  • 华东理工大学

Dates

Publication Date
20260512
Application Date
20251219

Claims (10)

  1. 1. A preparation method of a segmented polybenzimidazole copolymer containing hydroxyl and sulfonic acid groups is characterized by comprising the following steps: Adding an Eton reagent and 3,3' -diaminobenzidine into a reaction kettle in inert gas atmosphere, setting the rotating speed of a stirring paddle to be n 1 , heating the reaction kettle to be t 1 to dissolve the 3, 5-dihydroxyterephthalic acid, then adding the 2, 5-dihydroxyterephthalic acid into the reaction kettle, adjusting the rotating speed of the stirring paddle to be n 2 , heating the reaction temperature to t 2 for prepolymerization after the reaction kettle is completely dissolved, then reducing the temperature to t 1 , adding dicarboxylic acid monomer with sulfonic group into the reaction kettle, heating to t 2 for prepolymerization after the reaction kettle is completely dissolved, then rotating the stirring paddle to be n 3 , heating to t 3 for polymerization, Wherein the dicarboxylic acid monomer with sulfonic acid group is selected from 3,3' -disulfo- [1,1' -biphenyl ] -4,4' -dicarboxylic acid or 4, 8-disulfonic acid-2, 6-naphthalene dicarboxylic acid, The molar ratio of 3,3' -diaminobenzidine to 2, 5-dihydroxyterephthalic acid to dicarboxylic acid monomer with sulfonic acid group is 2:1:1, The rotation speed of the stirring paddle is 150-170 rpm, n 2 is 90-110 rpm, n 3 is 70-90 rpm, the dissolution temperature t 1 is 70-90 ℃, the pre-polymerization temperature t 2 is 110-130 ℃, and the polymerization temperature t 3 is 130-150 ℃; And (2) after the reaction is finished, cooling the reaction kettle to t 1 , pouring the viscous solution into ice water for precipitation, adding alkali liquor for washing to neutralize residual acid in the product, washing with water and ethanol for several times, and finally drying in a vacuum oven at 120 ℃ to obtain the block polybenzimidazole copolymer.
  2. 2. The method for preparing the hydroxyl-and sulfonic acid group-containing block polybenzimidazole copolymer according to claim 1, wherein the method comprises the following steps: wherein in the step (1), the Eton reagent is a mixture of phosphorus pentoxide and methane sulfonic acid, wherein the mass fraction of the phosphorus pentoxide is 7.2-8.2 wt%; the two times of prepolymerization are 2-3 hours, and the polymerization time is 3-4 hours.
  3. 3. The method for preparing the hydroxyl-and sulfonic acid group-containing block polybenzimidazole copolymer according to claim 1, wherein the method comprises the following steps: In the step (2), the kinematic viscosity of the viscous solution is 35000 cp-40000 cp; the alkali liquor is selected from any one of saturated sodium bicarbonate solution, saturated sodium carbonate solution, saturated potassium bicarbonate solution and saturated potassium carbonate solution; Washing the solution with alkali lye, water and ethanol to ph=7.0; the drying time was 24h.
  4. 4. A segmented polybenzimidazole copolymer containing hydroxyl groups and sulfonic acid groups, which is characterized in that the copolymer is prepared by the method of any one of claims 1 to 3 and is selected from any one of the following structural formulas: , m:n=3~7:3~7。
  5. 5. The segmented polybenzimidazole copolymer containing hydroxyl groups and sulfonic acid groups according to claim 4, where the intrinsic viscosity is not less than 3.0 dL/g, the weight average molecular weight is 150000-200000 g/mol, and the polydispersity index is 1.5-2.0.
  6. 6. A preparation method of a proton membrane is characterized by comprising the steps of dissolving the block polybenzimidazole copolymer containing hydroxyl and sulfonic acid groups in an aprotic polar organic solvent to obtain a membrane building solution containing the block polybenzimidazole copolymer with the concentration of 10-20wt%, pouring the membrane building solution on a smooth and flat membrane-forming plate, placing the membrane-forming plate into an 80 ℃ oven for solvent evaporation, drying, removing the membrane from a glass plate, soaking the membrane in an acid solution for proton exchange, washing the acid remained on the surface with deionized water, and placing the membrane-building solution into a 100 ℃ oven for drying to obtain the proton membrane of the block polybenzimidazole copolymer containing hydroxyl and sulfonic acid groups.
  7. 7. The method for preparing a proton membrane according to claim 6, wherein: Wherein the aprotic polar organic solvent is selected from any one of N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and tetrahydrofuran; the concentration of the block polybenzimidazole copolymer in the film building liquid is 15 wt%; The film-forming plate is selected from glass plates; the acid solution is 1.0 mol/L sulfuric acid; The thickness of the segmented polybenzimidazole copolymer proton membrane containing hydroxyl and sulfonic acid groups is 20-30 mu m; The solvent was volatilized for 24 hours, the proton exchange was carried out for 24 hours, and the drying in the oven was also carried out for 24 hours.
  8. 8. A proton membrane prepared by the preparation method of claim 6 or 7.
  9. 9. An energy storage battery diaphragm, characterized in that the segmented polybenzimidazole copolymer containing hydroxyl and sulfonic acid groups according to claim 4 or 5 is adopted, or the proton membrane according to claim 8 is used as the energy storage battery diaphragm.
  10. 10. An energy storage battery comprising the energy storage battery separator of claim 9.

Description

Block polybenzimidazole copolymer containing hydroxyl and sulfonic acid groups and preparation method and application of proton exchange membrane of block polybenzimidazole copolymer Technical Field The invention belongs to the technical field of preparation of proton exchange membranes of batteries, and particularly relates to a segmented polybenzimidazole copolymer containing hydroxyl and sulfonic groups, a preparation method of the proton exchange membrane and application of the segmented polybenzimidazole copolymer. Background Polybenzimidazole (PBI) is taken as a typical non-fluorine aromatic polymer material, has excellent mechanical strength and chemical stability, and is widely applied to the field of energy storage battery diaphragms. Most of PBI materials are prepared by polycondensation and cyclization of corresponding diamine and carboxylic acid, and have strong molecular chain rigidity and large inter-chain interaction force so as to ensure that the PBI materials have enough mechanical properties. But high molecular weight PBI polymers are often difficult to dissolve in common organic solvents, which not only results in the inability to synthesize ultra high molecular weight PBI by solution methods to enhance the mechanical properties of the film, but also makes it exceptionally difficult to produce large area, defect free high quality films. Commercial m-PBI, such as that prepared from 3,3' -Diaminobenzidine (DAB) and isophthalic acid (IPA), has high rigidity of molecular chains and strong inter-chain interaction, although excellent in thermal stability and mechanical strength, resulting in decrease of solubility in organic solvents with increase of molecular weight, which severely limits the feasibility of processing into films through solutions. In addition, the PBI material lacks an ion exchange group and combines a self compact structure, so that the intrinsic conductivity of the traditional PBI membrane is extremely low, the operation requirement of a battery is difficult to meet, and the PBI material can be used as a flow battery diaphragm after being doped with strong acid (such as phosphoric acid). Although acid doping can increase conductivity, it can result in a serious decrease in mechanical strength and stability of the membrane, thereby affecting the overall performance, service life, and long-term stability of the battery. In order to prepare PBI polymers of high molecular weight, good solubility and high conductivity, researchers have developed various synthetic strategies and modification methods such as modification of monomer structure, modification of main and side chain structure, construction of crosslinked network, blending of organic and inorganic materials, and porosification treatment, among which sulfonation treatment is one of effective means. The existing Sulfonated PBI (SPBI) improves the hydrophilicity and proton conductivity of the PBI membrane by introducing sulfonic acid groups into the main chain, but is mostly limited to introducing sulfonic acid groups which are a hydrophilic group, and proton and hydrogen bond sites provided by the sulfonic acid groups are limited, so that the proton conduction efficiency is not high. In addition, the sulfonated PBI is usually synthesized by adopting a random copolymerization mode, sulfonic acid groups are distributed irregularly, and the local hydrophilic areas are easy to be too dense to swell or even dissolve in operation, or the local hydrophobic areas are too large to prevent proton transmission. Meanwhile, the traditional sulfonated monomer (such as isophthalic acid-5-sodium sulfonate) has limited steric hindrance, has insufficient effect of damaging the regular accumulation of molecular chains and improving the solubility, and is difficult to synthesize a polymer material with ultrahigh molecular weight, excellent solubility, high proton conductivity and excellent mechanical strength and stability. Disclosure of Invention Aiming at the defects of the existing sulfonated PBI modification scheme, the invention aims to provide a brand new block polybenzimidazole copolymer, which fundamentally solves the problems, and the technical principle is that a multiple hydrogen bond network is constructed with imidazole rings by introducing sulfonic acid groups and hydroxyl groups simultaneously, so that the conductivity is improved and the excessive swelling of the membrane in water is inhibited; the block structure is utilized to induce the formation of a good microphase separation structure in the membrane, a continuous and efficient channel is provided for proton transmission, a series of rigid sulfonated diacid monomers with large steric hindrance are selected, intermolecular acting force is weakened, a close-packed structure of a polymer main chain is damaged, and the solubility of a high molecular weight polymer is improved. The first aim of the invention is to provide a segmented polybenzimidazole copolymer containing hyd