ORDERING AND MOBILITY OF FERROELECTRIC LIQUID-CRYSTAL DIMER AS STUDIED BY FT-IR SPECTROSCOPY WITH 2D-IR CORRELATION-ANALYSIS

Both a conservative rapid-scan FT-IR technique and a novel step-scan F T-IR technique with 2D correlation analysis were used to study the ori entation and the mobility of a ferroelectric liquid crystal dimer duri ng switching under an electric field. The detailed mutual arrangements of different molecular segments (mesogen, poly(methylene) chain, poly siloxane chain) in a smectic C phase were derived from the static spe ctra. It was shown that the long mesogen axis, the average poly(methyl ene) and the average polysiloxane chain axes do not coincide with each other. The hindered rotation of the carbonyl group is confirmed. Time -resolved FT-IR technique was used to follow the segmental motion with a time resolution of 5 mu s. The temperature and electric field stren gth dependencies of the mobility of these segments are discussed. 2D c orrelation analysis of time-resolved data reveals small differences in the behavior of the carbonyl and the benzoic rings in the mesogen moi eties, that can be explained as differences in the orientation distrib ution functions of these moieties.