Pseudo-polar order in the tilted smectic phases of bent-core hockey stick shaped molecules

Abstract

We discuss the liquid crystal phases of a compound consisting of bent-core hockey-stick-shaped molecules. The compound exhibits two smectic phases with an in-plane pseudo-polar order in addition to the tilt order in the layers. The transverse shape anisotropy and dissimilar arm lengths of these bent-core molecules stabilise these pseudo-polar tilted smectic phases. The higher temperature smectic phase has an anti-clinic organisation of the molecules in successive layers. An intermediate organisation between the synclinic and anti-clinic structures is found in the lower temperature smectic phase. We have developed a simple phenomenological model to account for these phases. In the higher temperature smectic phase, a field-induced Freedericksz type transition is observed beyond a threshold electric field. We also account for this field-induced transition using our theoretical model.