Wholly-aromatic amino acid, 3-amino-4-hydroxybenzoic acid (34AHBA), was derived from the culture media of genetically-manipulated Streptomyces griseus. 34AHBA is an exotic amino acid and unused in industry but has a potential as a monomer for high-performance polymers with a rigid structure. We previsously prepared a thermotropic liquid crystalline polyesters by a thermal polycondensation of hydroxyl and carboxyl groups of 34AHBA and another hydroxyacid derivative. However the resulting polyesters were too brittle to extend the researches and then we here change the concenpt of macromolecular design derived from 34AHBA into polybenzazoles which generally exhibit super-high thermoresistance and mechanical perofrmances. If all the functional groups of hydroxyl, amine, and carboxyl in 34AHBA are used, poly(2,5-benzoxazole) should be formed (Scheme 1a). At first we tried to optimize the polymerization condition of 34AHBA to produce the poly(2,5-benzoxazole)s according to the literatureand got the films. However we failed to get tough film presumably due to too rigid structure. Next we converted hydroxyl group of 34AHBA into amine to get 3,4,-diaminobenzoic acid (34DABA), in order to use the product as a monomer of poly(2,5-benzimidazole) and its derivatives. For this purpose, we used 2-bromoisobutyramide which was easily reacted with hydroxyl of 34AHBA to form ether bond and the resultant showed Smiles rearrengent under a certain conditon. After hydrolysis, we susscessfully got 34AHBA (Scheme 1b). By using bio-based 34AHBA and 34DABA, we made macromolecular designs for polybenzazoles with ultra-high thermostability and good toughness.

Ultra-high thermostability in polybenzazoles from wholly-aromatic amino acid

253rd National Meeting (2017)

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