Flow birefringence of polystyrenes with narrow molecular weight distributions

Abstract

The samples investigated were three anionic polystyrenes with molecular weights of 0.388·106, 1.14·106 and 1.59·106. Flow birefringence and extinction angle were determined as functions of the velocity gradient for dilute solutions in monobromo-benzene. The results were plotted in terms of coil expansion according toA. Peterlin. At low velocity gradients, the obtained expansions are in good accordance with the expectation based on the perfectly flexible subchain model (B. H. Zimm). When the extension of the average end-to-end distance of the coil is greater than 5%, further expansion of the coil with increased velocity gradient occurs at a lower rate than predicted by the said theory. No agreement, however, was found with the theoretical results obtained byR. Cerf with respect to the kinetic stiffness of the chain molecules.