Active and passive viscosities of a bent-core nematic liquid crystal

Abstract

We report the measurements of active and passive viscosities of a bent-core nematic liquid crystal. The active viscosity is measured using a rheometer and the passive viscosities are measured by measuring the self-diffusion coefficient of a microsphere in the aligned sample. The effective active viscosity is larger and the effect of presmectic fluctuations are observed much higher than the N–Sm-C transition temperature than commonly seen in calamitic liquid crystals. The temperature dependence of passive viscosities is stronger than that of active viscosities. The self-diffusion of the microsphere is reduced and appears to be non-Gaussian as the N–Sm-C transition is approached. The study of Brownian fluctuations is useful to understand the smectic fluctuations in bent-core nematic liquid crystals.