Comparison of shear-induced conductivity anisotropy in a micellar system in the isotropic and the nematic phase

Abstract

Conductivity measurements are presented in two isotropic micellar solutions and in the nematic phase of the sodium salicylate/cetylpyridimium chloride/H2O system under shear. For the isotropic solutions the concentrations studied correspond to the plateau behaviour in the flow curve for this system. The measured anisotropy in the shear-aligned isotropic solutions is at least one order of magnitude smaller than the anisotropy in the nematic phase. Time-resolved measurements show that the relaxation behaviour on shear start-up and on shear cessation is much faster in the isotropic solutions than in the nematic phase. The results suggest that the micelles in the shear-induced low viscosity phase are shorter than in the nematic phase.