Temperature Dependence of the Rotatory Power and Tilt Angle in a Ferroelectric Liquid Crystal with a Cholesteric-Chiral Smectic C Phase Sequence

Abstract

Recently it has been shown that the tilt angle in a S_c* phase can be determined from measurements of the optical rotatory power, birefringence and helical pitch. We have applied this procedure for studying the tilt behaviour of a ferroelectric liquid crystal which exhibits the phase sequence N*-S_c*. The tilt results are compared with those obtained for a planar sample from measurements of the angle between the dechiralization lines and buffing direction. A good agreement has been found between both sets of data, albeit the points obtained from the indirect method are much less scattered. In contrast to the tilt saturation commonly observed immediately on cooling through the N*-S_c* transition, we have clearly noticed a slight variation of this quantity within the S_c* phase, which cannot be appreciated from the direct angle measurements. It is argued that the apparent temperature independence of the tilt angle could be just a consequence of the wall anchoring effects in planar cells.