Universal law for the rotational viscosity of nematic liquid crystals

Abstract

The rotational viscosity ${\ensuremath{\gamma}}_{1}(T)$ of a nematic is of dominant importance for wide operating temperature display applications. In this paper we show that ${\ensuremath{\gamma}}_{1}(T)$ is, except for a small prefactor variation, a universal function of $T\ensuremath{-}{T}_{g}$ where ${T}_{g}$ is the glass transition temperature. In a mixture ${T}_{g}$ is a linear function of the component mole fractions and ${T}_{g}$ of a component can be predicted from molecular structure by a simple phenomenological model. ${\ensuremath{\gamma}}_{1}(T)$ of a mixture can thus be predicted from the molecular structures and concentrations of the components.