Optic and electro-optic investigations on SmQ, SmCA* and L phases in highly chiral compounds

Chiral molecules give rise to a large variety of mesophases. Well-known examples are cholesteric or ferroelectric smectic phases where the chirality tends to favor a macroscopic twist. Furthermore, the molecular core length (l) plays an important rôle on the range of the mesophases and on the temperature (TNI) for the onset of orientational order. The tendency for TNI is to increase (going over 200∘C for some compounds) with increasing l. We report in this paper on a selection of compounds which have been designed in order to favor an anticlinic smectic ordering together with high chirality. As a common feature, they have a long rigid core with four benzene rings and a chiral chain (usually the same) at each end. They display a locally anisotropic liquid phase referred to as “L phase” in a large temperature range between TNI and the low temperature SmQ or SmCA* phase. Optical rotatory power (ORP), birefringence and electro-optic studies have been performed with these compounds.