Phase Transition and Rheological Behavior of a Side-Chain-Type Liquid Crystalline Polysiloxane

Abstract

Temperature dependence of the viscosity for a neat sample of a side-chain-type liquid crystalline polysiloxane (LCS) was measured from the isotropic phase to the liquid crystalline phase. At temperatures much higher than the isotropic - liquid crystalline phase transition temperature (Tc) measured by a polarized optical microscope, the viscosity was almost independent of the shear rate, and it increased as the temperature decreased. At temperatures slightly higher than Tc the viscosity measured at shear rates of 3Os^-1 and 5Os^-1 decreased steeply as the temperature decreased. These results were discussed in terms of the shear-induced ordering of mesogens of the LCS even at the temperatures above Tc.