Ferroelectric-like behaviour of the SmCP phase in liquid crystalline compounds with asymmetrical bent-core molecules

Abstract

A new series of asymmetrical bent-shaped mesogens has been synthesised and their mesomorphic properties studied. All compounds exhibit the B₂ (SmCP) phase. For some compounds we found a very low coercive field for switching to the saturated ferroelectric state and only one peak in the switching current. Due to the lack of SHG signal in the zero field state and the behaviour of the relaxation mode we cannot unambiguously assign ferroelectric or antiferroelectric character to the B₂ phase observed. The observation of planar samples revealed a striped texture. Large optically active domains appear on very slow cooling, which are attributed to a non-homogeneous (twisted) in-plane structure imposed by surfaces. The twisted domains are suppressed under a critical electric field. A simple model of such a structure and its behavior in the electric field is proposed. The low temperature phase detected on further cooling is attributed to a crystalline-like smectic phase.