Liquid-crystalline properties of a chiral twin material possessing a remarkably flexible central spacer

Abstract

A novel chiral twin molecule, (R)-3-methyladipic acid bis{2-[4-(5-octyl-2-pyrimidinyl)phenyloxy]ethyl} ester (MAB-8-PYPOE), has been prepared and the effect of the spacer structure on the physical properties investigated. The phasetransition behaviour and helical twisting power of the molecule were compared with those of an analogous chiral twin molecule, (R)-3-methyladipic acid bis[4-(5-octyl-2-pyrimidinyl)phenyl] ester (MAB-8-PYP), which possesses a shorter central spacer. MAB-8-PYPOE shows a monotropic smectic A phase with a low melting point. Pitch measurements revealed that MAB-8-PYPOE induces a weaker helical structure in the cholesteric phase and particularly in the chiral smectic C phase than MAB-8-PYP. In binary mixtures between MAB-8-PYPOE and a smectic host liquid crystal, the transition behaviour induced by the twin molecule was found to be dependent on the structure of the host material.