Dielectric Regime of Electrohydrodynamic Instability in Nematic Liquid Crystals

Abstract

The frequency dependencies of the threshold voltage of electrohydrodynamic instability in nematic liquid crystals were investigated as functions of the dielectric anisotropy (-1.5 < σ < + 10), electric conductivity (10⁻¹¹ < σ < 5.10⁻⁹ ohm⁻¹ cm⁻¹) and anisotropy of the conductivity (1.1 < [sgrave]∥/[sgrave]σ < 1.8). Three types of the instability have been considered: a) for ε _a < O and the planar orientation at the frequencies above the critical one (“chevron” or dielectric regime); b) for ε_a > O and the homeotropic orientation at all the frequencies (the circular and fingerprint-type domains); c) in the isotropic phase. The threshold voltage in the nemataic phase was shown to be independent of the anisotropy parameters and the orientation of a liquid crystal and to coincide with the threshold of the instability in the isotropic phase. Thus, we came to the conclusion that the instability has the isotropic character in all the cases investigated.