Processable precursors .4. Synthesis and characterization of processable precursors to poly(phenylene bisbenzoxazoles)

Processable precursor polymers to poly(phenylene bisbenzoxazole)s (PBOs) have been prepared and studied. The precursor polymers were synthesized by the polycondensation of 1,4-bicyclo[2.2.2]octyl-2,5-diethanoate dicarboxylic acid or 1,4-bicyclo[2.2.2]octyl-2,5-diol dicarboxylic acid with 3,3'-dihydroxy-4,4'-diaminobiphenyl or 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in poly(phosphoric acid). The precursor polymers were characterized by solubility, viscosity, spectroscopy (infra-red, H-1 and C-13 nuclear magnetic resonance) and thermal analysis such as differential scanning calorimetry, thermogravimetric analysis and optical polarizing microscopy. Conversion of the more stable PBOs is achieved by pyrolysis in air or under argon atmosphere. (C) 1997 Elsevier Science Ltd.