Phase decomposition in poly-p-phenylene benzobisoxazole/amorphous nylon molecular composites

Abstract

Abstract Miscibility characteristics of poly-p-phenylene benzobisoxazole (PPBO)/amorphous nylon (AN) molecular composites were studied by means of differential scanning calorimetry (DSC), dielectric relaxation, wide-angle x-ray diffraction (WAXD), and light scattering. The solution-mixed PPBO/AN exhibited a systematic movement of a single glass transition temperature (T g) with composition in DSC and dielectric measurements, implying an entrapped single phase of the molecular composites. In the WAXD studies of the 50/50 mixture, two very weak reflection peaks of the PPBO phase and a small amorphous halo of AN were discerned. Light scattering studies showed no detectable level of orientation fluctuations. Upon heating, thermally induced phase separation occurred, with a cloud point phase diagram reminiscent of a lower critical solution temperature (LCST). As typical for entrapped single-phase blends, the phase diagram of LCP blends is irreversible. Nevertheless, several temperature jump experiments were un...