Viscometry of Nematic Liquid Crystals

Abstract

Viscometric experiments have played a significant part in establishing continuum theory for nematic liquid crystals. Such theory supports the hypothesis that observed non-Newtonian behaviour stems from competition between the aligning influences of flow and solid surfaces, and as a consequence predicts rather unusual scaling for the apparent viscosity. This paper first describes such scaling and its subsequent experimental confirmation emphasising the full implications of the latter. The relevance of the theory thus established, there follows a simple analysis of alignment in shear flow which leads to conditions on material coefficients necessary to ensure consistency with observations. Our discussion turns next to an account of solutions exhibiting non-Newtonian behaviour, and also mention of a recent stability analysis which attempts to discriminate between the different solutions that are possible. The final section considers oscillatory shear flow and presents an analysis of an instability which can occur in certain nematics.