The smectic A-smectic C* phase transition in submicron confined geometry

Abstract

The influence of confined geometry on the smectic A-smectic C* phase transition in the ferroelectric liquid crystal CE8 has been analysed. Using an electro-optic response technique, the temperature dependence of elementary excitations in thin, homogeneously aligned, wedgetype cells of thickness from 0.25 to 4mum has been measured for different thicknesses of the aligning layer. In the case of a thin aligning layer (15nm), we observe in the smectic C* phase an increase of the relaxation rate of the phase excitations and a decrease of the phase transition temperature, both of which are proportional to the inverse of the cell thickness. For a thick aligning layer (50 nm), the relaxation frequency and the transition temperature are proportional to the inverse square of the cell thickness. This indicates that the surface anchoring energy depends on the thickness of the aligning layer. For CE8 on nylon, we obtain a surface anchoring energy W=10-4 Jm-2 for a thin aligning layer, and strong anchoring with W>5x10-4 Jm-2 for a thick aligning layer.