THE INVESTIGATION OF THE RELAXATION PROCESSES IN ANTIFERROELECTRIC LIQUID-CRYSTALS BY BROAD-BAND DIELECTRIC AND ELECTROOPTIC SPECTROSCOPY

Wide band dielectric and electro-optic spectroscopy of an antiferroele ctric liquid crystal (AFLC) has been carried out over a range of frequ encies from 1 kHz to 1 GHz. The AFLC sample under investigation posses ses a variety of different ferri-, ferro-, and antiferro-electric phas es. Dielectric spectroscopy of the LC cells in the antiferroelectric p hases reveals both collective and individual dynamics of molecules. In the antiferroelectric SmCA phase, three dielectric relaxation process es are found in the absence of the bias and an additional relaxation p rocess appears under the bias field. A solution of the dynamical equat ion of the director subject to a weak alternating held for the anitfer roelectric helix has been found. A comparison of the results of electr o-optic and dielectric spectroscopy with a theoretical study enables a determination of the origin of the relaxation processes in antiferroe lectric phases. The mechanism for the distortion of the antiferroelect ric helix has been determined using dielectric spectroscopy and a non- linear electro-optic technique.