Microstructural study of as-extruded and heat-treated ribbons of poly(p-phenylene benzobisthiazole)

Abstract

Ribbons of poly(p-phenylene benzobisthiazole) (PBT) prepared by extrusion from methane sulphonic acid solution into acid-water coagulation baths, were examined by electron microscopy, wide-angle X-ray scattering and small angle X-ray scattering. Electron diffraction patterns and corresponding dark-field images of as-extruded ribbons suggest that the chains are well oriented in the extrusion direction, with laterally-ordered regions averaging 2 nm in width. Upon heat treatment, the equatorial reflections sharpen and dark-field imaging indicates an increase in lateral order to about 15 nm. Small-angle X-ray scattering patterns show very little scattered intensity except for strong equatorial scattering attributed to voids elongated parallel to the extrusion direction. The absence of distinct crystalline images in 0 0l dark-field is supporting evidence for axial shift of the molecules along the chain axis, as suggested by previous diffraction studies.