Tilt angle, polarization, susceptibility and landau expansion coefficients for multicomponent ferroelectric liquid crystal mixtures

Two multicomponent liquid crystal mixtures showing the second order smectic A-ferroelectric smectic C* phase transition and high spontaneous polarization in the chiral smectic C* phase have been studied with an aim to figure out whether the Landau expansion may be applicable to multicomponent mixtures. The electro-optical and pyroelectric techniques were used for measurements of the tilt angle and polarization, respectively. The tilt-polarization coupling constants were determined for a wide temperature range in both the smectic A and C* phases. The first coefficient of the Landau expansion has been calculated from the temperature dependence of the soft mode susceptibility and the second one has been found from the spontaneous tilt angle (order parameter) in the smectic C* phase. The parameters measured are compared with those known for classical single component ferroelectric liquid crystals.