Dynamic birefringence in solutions of polynaphthoileneimidobenzimidazole during hydrolytic thermal degradation

Dynamic birefringence in solutions of polynaphthoileneimidobenzimidazole subjected to hydrolytic thermal degradation in 96% sulfuric acid was studied. The polymer in solution was preliminarily heated at different temperatures between 65 and 120°C. It was then examined at 22°C using dynamic birefringence and viscometry. The intrinsic viscosity of solutions and the molecular mass of the fragments resulting from thermal degradation were both found to decrease with an increase in the treatment temperature. At the same time, the shear-optical coefficient first increased and then, at treatment temperatures exceeding 90°C, decreased in parallel with a decrease in intrinsic viscosity. Various causes of the discovered anomaly are discussed