Abstract
Abstract Phase relationships in concentrated solution and in the bulk of a solvent/rigid-rod/flexible-coil system were investigated. The solvent was a mixture of two strong acids. The rigid-rod polymer was poly-p-phenylenebenzobisthiazole (PBT). The flexible-coil polymer was poly-2,5(6)benzimidazole (ABPBI). The concentrated solution and bulk morphologies were investigated by means of polarized optical microscopy, small-angle light scattering, scanning electron microscopy, and wide-angle x-ray diffraction techniques. Above a critical concentration, Ccr, the pseudo ternary solution separated into two coexisting phases, one optically anisotropic (liquid crystalline) and the other isotropic. The anisotropic domains were highly birefringent. They contained primarily the PBT macromolecules oriented perferentially along a domain axis. Numerical values of Ccr, determined experimentally, were in good agreement with calculated predictions. Aggregates composed of PBT molecules were observed to be dispersed in a con...
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