Stability of nematic liquid crystals under a temperature gradient. Calculations for PAA

Abstract

Abstract The aim of this article is to report the striking difference between the behavior of a classical fluid layer and a nematic liquid crystal layer under a temperature gradient: two critical temperature gradients, a positive and a negative, are found for the loss of stability in a nematic layer, corresponding respectively to a hotter bottom and a hotter top. This last case is impossible for classical isotropic fluids. Nematics are predicted to be less stable than isotropic fluids with comparable viscosity. Numerical results are predicted for PAA for the molecular axes being parallel and perpendicular to the layer and the latter case is found to be much less stable than the former, in accord with physical intuition.