Dielectric study of a ferroelectric liquid crystal at high pressure

Abstract

We report the effect of hydrostatic pressure on the transverse static dielectric constant €1 of a ferroelectric liquid crystal. The measurements performed in the frequency range 0.05-40 kHz show that at constant temperature, ει increases with increasing pressure. However, at any given relative tempera- ture with respect to the smectic A - smectic C' (A - C*) phase boundary, the value decreases drastically with increasing pressure. Furthermore, the profile of the temperature dependence of €1 also undergoes considerable change at high pressures. The results indicate this behaviour to be due to a decrease in the Goldstone mode and soft mode relaxation frequencies with increasing pressure. The rotational viscosity associated with the azimuthal rotation of the molecule increases with increasing pressure and appears to be responsible for the ob- served Goldstone mode behaviour. Analysis of the data in the A phase enable the determination of the parameters controlling the soft mode relaxation.