Dielectric properties of ferroelectric liquid crystals

Abstract

We performed dielectric- and electrooptical measurements of a ferroelectric liquid crystal film as a function of temperature, frequency and bias field. Starting with the homeotropic texture, obtained with a silane coating, we measured the dielectric properties in the direction of the helical axis. After realigning to a bookshelf texture¹ we measured the collective modes for the director fluctuations (soft- and Goldstone modes) perpendicular to the helical axis. With additional measurements of the spontaneous polarization, the director tilt angle and the helical pitch we determined the rotational viscosity of the Goldstone mode and the twist elastic constant² for different temperatures. The dielectric biaxiality is negative over a wide temperature range, but the in-plane anisotropy is smaller and changes it's sign.