| Abstract: | Liquid crystalline solutions of poly (p-phenylene benzoxazole) (PBO) in polyphosphoric acid (PPA) were prepared and studied. The typical banded texture and disclination of sheared PBO/PPA solution were observed by polarizing optical microscopy (POM), and the microstructure of the periodic aligned polymer chain that induced the texture was investigated by scanning electron microscopy (SEM). Spherulite structure was found in the PBO/PPA system with little shearing. Differential scanning calorimeter (DSC) analysis on the system revealed the existence and melting behavior of two ordered phases. An exothermic peak at 85°C was interpreted as the enhancement of the interaction between PBO molecules and PPA solvent, and the endothermic peaks at 140 to 150°C and 180 to 200°C are explained as the melting of the ordered phases. The changes of small-angle light scattering (SALS) patterns of PBO/PPA solution at different temperature further supported these results. |
