Calculation of the Dielectric Constant of a Ferroelectric Liquid Crystal From a Mean Field Model

Abstract

The static dielectric constant epsilon(perpendicular to) of the ferroelectric liquid crystal 4-(3-methyl-2-chlorobutanoyloxy)-4'--heptyloxybiphenyl (A7) with high spontaneous polarization is calculated as a function of temperature using a mean field model. This calculation is performed close to the smectic A-isotropic liquid (SmA-I) transition for pure optically active compound (T-c = 81.6 degrees C). For this calculation of epsilon(perpendicular to), the free energy of the SmA phase is expanded in terms of the orientational order parameter. and spontaneous polarization P with P-2 psi(2). It is shown here that our model describes adequately the observed behaviour of the temperature dependence of epsilon(perpendicular to) close to the SmA-I transition for A7.