Isotropic liquid–ferrielectric smectic C phase transition observed in a chiral nonsymmetric dimer

Abstract

Ferrielectric smectic C phases are sub-phases intermediate between the ferroelectric and antiferroelectric phases. Their temperature range is narrow and depends on optical purity. We have recently reported a chiral nonsymmetric dimer exhibiting two ferrielectric phases with a wide temperature range. Ferrielectric-like ordering was observed, even in a racemic mixture of the enantiomers. We have now prepared a modified version possessing an alkoxy tail, (R)-1-methylheptyl 4′-{8-[4-(5-octyloxypyrimidin-2-yl)phenyloxy]octanoyloxy}biphenyl-4-carboxylate, and have investigated its physical properties using optical microscopy and differential scanning calorimetry. This nonsymmetric dimer was found to exhibit a direct transition from isotropic liquid to the ferrielectric chiral smectic C phase. Two ferrielectric smectic C phases, the antiferroelectric phase and chiral smectic I phase were present. The temperature range of the enantiotropic ferrielectric phases of the compound was about 28 K. The stabilisation of the ferrielectric phases is discussed in terms of chiral recognition and electrostatic interaction between molecules in adjacent layers.