Polar phases in chiral thiobenzoate liquid crystals

By dielectric measurements, the temperature scan method and studies of optical hysteresis loops, the phase sequences have been elucidated for two new compounds from a series of homologues containing a thiobenzoate group with a fluoro substituent in the first benzene ring (denoted nFHTBBM7*). Both compounds (n = 11 and n = 12) exhibit antiferroelectric (S-CA*) ferroelectric (S-C*) and several ferrielectric (S-CFI) phases, as well as the (S-C alpha*) phase. Also, in the compound 11FHTBBM7*, a metastable ferrielectric phase may appear in the temperature range of the antiferroelectric phase. The dielectric relaxation study revealed contributions to the dielectric constant from several modes detected in the temperature range studied. The properties of the relaxation modes and the phase transition sequences of the two compounds have been compared with those of the homologues with n = 9 and n = 10 studied previously.