Electroclinic measurement of the coefficients of Landau expansion of some ferroelectric liquid crystals

Abstract

The electroclinic effect in the smectic A phase of ferroelectric liquid crystals is a sensitive probe for measuring the soft mode response near the A-C^∗ transition point. It is possible to evaluate several coefficients of the Landau theory describing the A-C^∗ transition by simultaneously measuring the frequency dependence of both the optical signal and the current through the sample. We have made such measurements on a couple of homologous series [2S,3S]-4'-(2-chloro-3-methyl pentanoyloxy) phenyl-trans-4"-n alkoxy cinnamates synthesized in our labortory. The results show that the Landau meanfield theory is adequate to describe the A-C^∗ phase transition in these compounds.