Preparation And Characterization Of Imidazole-type Basic Anion Exchange Membrane

Imidazole anion exchange membranes have been extensively studied as an important component of alkaline fuel cells.This type of research is mainly divided into two categories,one is the imidazole group on the polymer backbone,the most representative of which is the anion exchange membrane of polybenzimidazoles.The other one is that the imidazole groups are grafted onto the polymer backbone through other chemical bonds.The main research direction in this category is the synthesis of more complex imidazole derivatives.The main problem with the above-mentioned in first type of anion exchange membrane is that the ion conductivity is low and the processing performance is poor.The problem with the second type of anion exchange membrane is the poor alkaline resistance of imidazole,which is easily decomposed by the attack of hydroxyl radicals under alkaline conditions.For these problems mentioned above,we synthesized two novel polybenzimidazole type anion exchange membrane materials and eight structurally stable imidazole derivative anion exchange membrane materials.The main conclusions are as follows:(1)Polybenzimidazole copolymer containing piperazine unit and its film properties.A PZDT monomer containing piperazine units was designed and synthesized.A series of polybenzimidazole anion exchange membranes were synthesized by block copolymerization with isophthalic acid and biphenyltetramine.The membranes were tested for ion conductivity and alkali resistance.With the increase of PZDT content,the ionic conductivity of the membrane also increased,reaching 44.6mS/cm at 80℃.After 120 days of immersion in 1M KOH at 60℃,the ion conductivity remained 67.87%.(2)Polybenzimidazole copolymers containing homopiperazine structural units and their membrane properties.A DMDB structural monomer containing a high piperazine structural unit was designed and synthesized.A series of anion exchange membranes containing homopiperazine were synthesized by block copolymerization with isophthalic acid and biphenyltetramine.The structures and performance of these films were tested.With the increase of DMDB content,the solubility of the series of polymers is improved,and the ionic conductivity also increases,and it can reach up to 45.5mS/cm at 80℃.The membrane was immersed in a 1 M KOH solution at 60℃.After 120 days,the ionic conductivity remained at 50%.(3)Study on polyphosphazene membrane materials containing imidazole derivatives.Eight different imidazole derivatives were synthesized by the Debus method.After quaternization,these functional groups were grafted onto the polyphosphazene backbone to prepare 8 kinds of imidazole derivative polyphosphazene anion exchange membranes.Structural characterization and performance testing of these films were performed.At 80℃,the ion conductivity can reach 56.63mS/cm.The membrane was immersed in a 1 M KOH solution at 60℃.After 120 days,the remaining ion conductivity was 97.03%.