Temperature dependence of flow birefringence in some aromatic liquids

Abstract

The variation of flow birefringence with temperature in the range 10–50°C has been determined for the aromatic liquids benzene, p-xylene, n-butyl benzene, diphenyl ether, dibenzyl ether and disphenylmethane. The derived relationship between stress optical coefficient â–½ and reciprocal absolute temperature is anomalous for each liquid in the context of existing orientation theories, which predict linear â–½, 1/T dependence with positive slope. Experimentally, a definite curvature is obtained with in most cases a maximum in â–½. Benzene exhibits a negative slope throughout the temperature range studied. Non-Arrhenius viscosity of those liquids other than benzene and p-xylene form a basis for postulating molecular clusters. The Raman-Krishnan theory is modified accordingly and for diphenyl ether predicts a maximum for â–½ whose position is in reasonable agreement with that observed.