Rheology and topological defects in dissipative structures in liquid crystals

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The apparent viscosity of nematic liquid crystals under the electro-hydrodynamic convection(EHC) has been investigated experimentally. When the EHC is induced, the apparent viscosity increases and then decreases as the increase of applied voltage. The peak voltage of viscosity does not depend on the transition voltage at which many topological defects appear and the decrease of viscosity happens in the second type of turbulent state. By adopting the Ericksen-Leslie theory, it is speculated that the anisotropy of turbulent state created by the shear field makes the shear stress relevant to the electric field negative, which reduces the apparent viscosity of the liquid crystal.