Time-resolved polarized FTIR-spectroscopy on structure and mobility in banana-shaped liquid crystal molecules

By use of time-resolved polarized Fourier-transform infrared (FTIR-) spectr oscopy the molecular structure and mobility of B2 phase LC banana-shape mol ecules is investigated. Two samples are investigated: an achiral banana-sha ped (B14) system and a mixture of achiral (B14) and chiral (B7*) banana-sha ped molecules. The molecules are oriented by shearing the substance between ITO-coated CaF2 windows. The measurements give detailed information about a) the average orientation, b) the orientational order, c) the reorientatio n time, d) the reorientation angle and e) the phase relation between the di fferent segments for the different molecular moieties. The experiments are performed in dependence on frequency and strength of the external electric field. The corresponding molecular response of the different moieties is re corded by means of step-scan FTIR spectroscopy with a time resolution of 5 microseconds.