MORPHOLOGY AND MECHANICAL-PROPERTIES OF A PHASE SEPARATED AND A MOLECULAR COMPOSITE 30-PERCENT PBT 70-PERCENT ABPBI TRIBLOCK COPOLYMER

The morphology of a triblock copolymer of 30% rigid-rod poly(p-phenylene benzobisthiazole) (PBT) and 70% semi-flexible coil poly(2,5(6)benzimidazole) (ABPBI) was examined by wide angle X-ray scattering and scanning and transmission electron microscopy. Samples that were vacuum cast from a solution formed a microphase separated film with 0. 1 mu m particles and platelets of well-oriented 10 nm PBT crystallites in a ductile ABPBI matrix. Fibers were dry-jet/wet-spun from an optically homogeneous solution into a water coagulation bath to inhibit large scale phase separation. Heat-treated fiber contained crystallites of PBT and ABPBI with lateral dimensions no larger than 3 nm, demonstrating that PBT molecular segments were well dispersed and that a rigid-rod, molecular level composite had been achieved.