Abstrato

Electrical excitation of ferroelectric liquid crystal studied by infrared spectra

M.M.Jamshidi*, F.Akkari

The behaviour of molecular orientation for a homogenously aligned cell of a ferroelectric liquid crystal mixture in Smectic C* (SmC*) phase is investigated using FTIR spectroscopy. This paper studies the main molecular mechanismand structure of the mixture. For this, the polarisation dependence of the absorbance for the core carbonyl (C=O) and phenyl (C=C) stretching bands for various stages of the electrically induced transformation of the sample structure is analysed until the complete unwinding of helix is formed. The angular shift of the absorbance profile for core carbonyl and phenyl bands is found to be dependent on the applied field and its value is found as the dc voltage is altered across the liquid crystal cell. The effects of ionic separation and hysteresis are found to be the cause for the existence of a non-zero value in apparent tilt angle at zero applied voltage. The value of the dichroic ratio and polarisation angle for both the core carbonyl and phenyl groups are calculated and the key results are explained and discussed.