Time-resolved infrared spectroscopic study of the orientation behavior of liquid crystalline molecules in the presence of an electric field

Time-resolved Fourier-transform infrared spectroscopy is used to follow the changes induced by electric field in molecular orientation of a 4-n-pentyl-4′-cyanobiphenyl (5CB) liquid crystal. At an electric field strength greater than 600 V cm^?1, the long axis of a 5CB molecule orientates to the direction of the electric field. The orientation function, however, saturates at a field strength greater than 1000 V cm^?1. The relaxation time of the rise amd decay processes was in the range of 0.04–0.24 s and a decreased with increasing field strength. The orientation/relaxation process is discussed on the basis of the motion of liquid crystal domains.