The effects of a second branched alkyl chain and double chiral centres on the phase transition and spontaneous polarization of a chiral smectic liquid crystal

Abstract

The effects of a second branched alkyl chain, lateral substitution, and double chiral centres on the phase transition and spontaneous polarization of the ferroelectric liquid crystal having a 2-methylalkanoyl group have been investigated. The introduction of another branched alkyl chain away from the 2-methylalkanoyl group causes a sharp S_C∗-S_A transition peak and also enhances the ferroelectric properties in the S_C∗ phase. Since the order within the layers is liquid-like in the S_C∗ phase, the alkyl chain branching away from both the chiral centre and a polar group affects the overall motion of the molecule in the S_C∗ phase. In the system of a compound with double chiral centres, the existence of the chiral centre in the 2-methylalkanoyl group affects the phase transition temperatures and the magnitude of the spontaneous polarization in the S_C∗ phase. On the other hand, the existence of the chiral centre in the 2-methylbutyl group only affects the stability of a more highly ordered smectic phase appearing below the S_C∗ phase.