A novel class of proton exchange membrane materials, sulfonatedpoly(phthalazinones), were prepared by modification of poly(phthalazinone).Sulfonation reactions were conducted at room temperature using mixtures of 95-98%concentrated sulfuric acid and 27-33% fuming sulfuric acid with different acidratiosin order to get SPPEK with degree of sulfonation (DS) in the range of 0.6 to1Ø Thepresence of sulfonic acid groups was confirmed by FT-IR analysis, and the DSandstructures were characterized by NMR. The introduction of sulfonic groups intothepolymer chains led to an increase in the glass transition temperature and adecrease inthe decomposition temperature. Membrane films were cast from solution inN,N--dimethylformamide or N,N-dimethylacetamide. Water uptakes and swellingratios ofthe membrane films increased with DS and sulfonated polymers with DS 1.2werewater soluble at 80°C. Proton conductivity increased with DS andtemperature up to95°C, reaching 10 -2S/cm.
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