Synthesis And Properties Of Sulfonated Polybenzoxazoles And Sulfonated Polybenzimidazoles

Sulfonated polybenzoxazoles and sulfonated polybenzimidazoles have goodheat resisting property, chemical stability and mechanical property. They can beused as the material for proton exchange membranes in fuel cells. As the core part ofproton exchange membrane fuel cells, the content of sulfonic acid groups is theguarantee to the electrical conductivity of proton exchange membrane fuel cells.However, a high degree of sulfonations will directly influence the thermal stabilityand solubility of the polymer. So, it will be difficult to make a ploymer menbrance.In this paper, by changing the content of sulfonic acid groups in sulfonatedpolybenzoxazoles and sulfonated polybenzimidazole, the influence on thesulfonation degree will be analyzed systematically.In this paper, by changing the ratio of the monomers, two series of variablesulfonated polybenzoxazoles and sulfonated polybenzimidazole polymer wassynthesized in the fixed concentration of poly phosphoric acid, and some methodssuch as Fu Liye transform infrared spectroscopy and1H NMR analysis test wereused to characterize the two series of sulfonated polymer, confirming the synthesisof the target product. The results of test show that the degree of sulfonation has acertain influence on the molecular weight of the polymer. Temperature of thepolymerization and the mass of fraction phosphorus pentoxide in poly phosphoricacid have a certain effect on sulfonated polymer of the two systems in preparation.This paper has studied the structure, thermal stability and molecular weight intwo kinds of sulfonated polymer, with the degree of sulfonation changing. Throughthe thermal analysis method,it can be finded, with the degree of sulfonationdecreasing, the thermal stability of polymer decreases, and the chain, group’sdistribution, crystallinity of the sulfonated polymer will change. The molecularweight of the sulfonated polybenzoxazole and the degree of reaction will decreasewith the degree of sulfonation decreasing. The preparation of sulfonatedpolybenzoxazole, weight retention rate is above58%in800oC. The preparation ofsulfonated polybenzimidazoles, weight retention rate was more than56%in800oC.Two kinds of polymerization has excellent thermal stability. With the increase oftemperature, proton conductivity increases. In the100oC, of which the degree ofsulfonatio is60%, the proton conductivity is0.14S/cm.