Ferroelectric and antiferroelectric modes in a new chiral thiobenzoate liquid crystal

This work concerns the dielectric relaxation study of a new compound containing a thiobenzoate group with a fluoro substituent, which presents a sequence of antiferro-, ferri-, ferroelectric and S-C alpha* phases. The polar character of these phases was confirmed by optical hysteresis loops. Three modes with a nearly monodispersive behaviour were identified: the soft mode, the Goldstone mode and a non-collective azimuthal mode. The soft mode softens above the S-A-S-C alpha* transition and triggers another mode within the S-C alpha* phase. Moreover, a collective anti-phase azimuthal mode appears and may be the origin of the onset of the antiferroelectric S-CA* phase. A strong influence of surface interactions on the thermal hysteresis and on the dielectric constant was evident in this work.