Polyphenylene‐1,3,4‐oxadiazoles have been prepared from benzenedicarboxylic acids or their derivatives and hydrazine by solution polycondensation in fuming sulfuric acid or polyphosphoric acid. These polymers were characterized by good thermal stability, and the molecular weights attained were high enough for the products to exhibit fiber‐or‐film‐forming properties. Concentrated sulfuric acid and polyphosphoric acid were the only solvents for these polymers.
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Iwakura et al. (1965) studied this question.
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