Transient Behavior of Domains in Liquid Crystals

Using an optical technique the formation and decay of domains in high applied electric fields has been studied for two nematic liquid crystals, p-azoxyanisole and p-butoxybenzoic acid. The decay time was found to be independent of the applied field but proportional to the sample thickness over the range studied. The rise time exhibited a d2/V type dependence on sample thickness (d) and applied voltage (V). This behavior is also found in solid ferroelectrics at high fields where domain propagation is the limiting switching factor. A phenomenological theory of domain kinetics was structed in the spirit of the Debye relaxation theory which accounts for the essential features of the experimental data. A justification for this approach was also found in its ability to account for the very low-frequency (<500 cps), large signal-dispersion data for these materials which featured a thickness dependence of the relaxation time.