Preparation and Characterization of Fibers Based on Poly(p-Phenylene Benzobisoxazole)s Containing Trifunctional Moiety as Chain Extender

Abstract

A series of poly(p-phenylene benzobisoxazole) (PBO)-based copolymers containing a trifunctional moiety in their backbones were prepared via polymerization of 4,6-diaminoresorcinol dihydrochloride (DAR) with terephthaloyl chloride (TPC) and 1,3,5-benzenetricarbonyl trichloride (BTC) in poly(phosphoric acid) (PPA). The concentration of trifunctional BTC comonomer was controlled during polymerization to be 0.0-2.0 mol% of difunctional TPC concentration. The inherent viscosity and associated average molecular weight of PBO copolymers with different BTC contents were evaluated by using solution viscometry and the Mark-Houwink equation, respectively. In addition, single fibers based on neat PBO and its copolymers were prepared by in situ dry-jet wet spinning of anisotropic liquid crystalline polymerization products in PPA dopes. The molecular structure and morphology of the as-spun fibers were determined. The effects of BTC content on the thermal stability and tensile mechanical properties of the as-spun fibers were also investigated.