Ferroelectric properties of liquid-crystalline S_C* phases induced by optically active cyanocyclohexylcyclohexanone derivatives

Abstract

Derivatives of optically active cyanocyclohexylcyclohexanone have been synthesized and used as dipolar chiral dopants to induce ferroelectric S_C* phases in an achiral host phase. The dopant molecules are the first examples in which the chiral centres are incorporated into a rigid core with transverse dipoles directly attached. The spontaneous polarization P _s and the tilt angle θ of the induced S_C* phases have been measured. P _s is strongly influenced by the relatively small changes of the molecular structure of the cyclohexanones, for example a change of the sign of P _s or a vanishing value of P _s. These effects are discussed in terms of a sterically hindered rotation of the dopant molecules around their long axes and explained by the assumption that the transverse dipole must not be necessarily parallel to P _s in the equilibrium state of rotation.