Unsteady Characteristics and Orientational Distributions of Polymeric Liquid Crystalline Flows.

Abstract

The molecular theory of Doi is employed to analyze numerically the unsteady simple shear flow of polymeric liquid crystals. Both the shear stress and the first normal stress difference exhibit an overshoot during the transient behavior. The order parameter also shows an overshoot phenomenon, which is almost the same as that for the first normal stress difference. Contrary to these quantities, the preferred angle of molecules does not express an overshoot but decreases monotonically with time. The overshoot rate decreases remarkably with the mean field potential, which implies that an overshoot phenomenon is not observed for strongly oriented polymeric liquid crystals. While the orientational distribution function under equilibrium conditions takes a symmetric form, it is sharpened and its symmetry is broken in the shear flow. Less molecules exist above the angular position, where the orientational distribution function is maximum, than below the angular position.