Abstract: The invention is a condensation polymerization reaction in which functionally terminated polybenzazole ligomers are reacted in a solvent acid at a temperature of at least 150.degree. C. and a shear of at least about 10 sec..sup.-1 under conditions so that the desired molecular weight is reached in no more than about 4 hours. The oligomers may be, for example, derived from the reaction of 4,6-diaminoresorcinol bis(hydrochloride) and terephthalic acid. The concentration of oligomers is high enough so that the reaction mixture contains liquid crystalline domains.

Abstract: Polybenzazole polymers can be synthesized rapidly in large quantities at high molecular weight and high concentration by a two-step process of forming oligomers in a batch reactor and advancing the molecular weight of the polymer in an extruder.

Abstract: It is advantageous to prepare oligomers of polybenzazole polymers by reaction of AA-PBZ monomer with an excess of BB-PBZ monomer. The resulting oligomer dopes may be stored at a temperature at which they remain pumpable until such time as the dope can be advanced to higher molecular weight by adding additional AA-PBZ monomer. The molecular weight of the polymer may be adjusted by controlling the amount of chain extender and/or chain terminator added to oligomer mixtures as they are advanced to final molecular weight.

Abstract: Polybenzazole polymers can be advanced rapidly to high molecular weight at relatively high temperatures and high shear in a dehydrating solvent acid.