Deformations of a Planar Nematic-Isotropic Interface in Uniform and Nonuniform Electric Fields

Abstract

The electric field-induced deformations of a planar nematic(N)-isotropic(I) interface were studied, using a surface-nucleated N film prepared in a usual sandwich-type cell. When the applied AC voltage (10 Hz-100 kHz) was small, a uniform elastic distortion of the director was observed. But. at higher voltages, the planar interface became unstable and a striped pattern. having periodicity of a few hundred micrometers. appeared mostly along the rubbing direction of the substrate. The striped pattern was essentially static and was found to correspond to the undulation of the interface. The instability is interpreted in terms of the hydrostatics of nematics, and coupling between the N-I interface and the director is shown to be large responsible. The deformation of the interface in an intentionally nonuniform electric field was also observed. Based on a simple estimate of the interface profile, the N-I interfacial tension was evaluated to be 2.1 × 10-2 erg/cm2.