MICROSCOPIC ORDERING IN SMECTIC PHASES OF LIQUID-CRYSTALS

Orientational order in smectic phases of a ferroelectric liquid-crystalline material 4′-(2S, 3S)-2″-chloro-3″-methylpentanoyloxyphenyl-4-decyloxy thiobenzoate, abbreviated 10̄.S.C1Isoleu, was examined by IR absorption spectroscopy. Oriented samples were prepared in both bookshelf and homeotropic alignment geometry. Several stronger IR vibrations were selected characterizing different parts and orientations of the molecules. Results show that the molecular tilt of the core parts of the molecules changes very little from the SA to the SC phase implying that the core parts of the molecules are already tilted in the SA phase. Axes of the core parts, that are disordered on a cone in the SA phase, start to align with each other but remain on this cone on lowering the temperature into the SC phase. The model agrees with some previous results.