Dielectric and electro-optical properties of a photosensitive liquid crystal

Abstract

The temperature dependencies of the dielectric and electro-optical properties of a pure photo-ferroelectric liquid crystal have been investigated, in the chiral smectic C (SmC*) phase, with and without ultraviolet (UV) illumination. The SmC* dielectric Goldstone mode characteristics, the spontaneous polarization, the tilt angle and the rotational viscosity are affected by UV irradiation. Under increasing UV light intensities the dielectric strength ΔϵG increases whereas the relaxation frequency fG , the spontaneous polarization P s, the electro-optical rotational viscosity γeo and the tilt angle θ decrease. The twist elastic constant K 3 and the Goldstone mode rotational viscosity γG of the studied compound are deduced from dielectric experimental results. Good agreement was found between both viscosities. The observed dielectric behaviours are controlled by the elastic constant and the rotational viscosity variations.