Interfacial Effects on the Viscosity of a Nematic Mesophase

Abstract

Abstract The effects of interfacial orientation on the viscosity of nematic p-azoxyanisole have been studied. Viscosity was measured in four glass capillary tube viscometers with diameters ranging from 78μ to 516μ. The surfaces of the capillaries were subjected to two standardized pretreatmenta—acid cleaning or acid cleaning followed by rubbing with a fiber—in order to produce different interfacial orientations. Both treatments resulted in non-Newtonian viscosity behavior and a dependence of viscosity on tube diameter not in agreement with that predicted for a homogeneous fluid. However, it was found that the treatment of the interface had a profound effect on viscosity. Non-Newtonian viscosity and diameter effects were much more striking in the caw of interfaces subjected to acid cleaning only. The significance and implications of these findings is discussed.