ANALYSIS OF DIELECTRIC-RELAXATION PHENOMENA WITH MOLECULAR ORIENTATIONAL ORDERING IN MONOLAYERS AT THE LIQUID-AIR INTERFACE

Starting from the Debye theory of rotational Brownian motion, we analy zed the dielectric relaxation phenomena with molecular orientational o rdering in Langmuir film on a water surface, assuming that the orienta tional distribution of the constituent rodlike polar molecules is rule d by Boltzmann statistics. The transient behavior of the polar molecul es induced by the application of step compression at the molecular are a A=A(i)(<A(c)) is discussed with taking account of the friction const ant of monolayer xi, and the dielectric relaxation time tau. Here A(c) is the critical molecular area defined as pi l(2) (l: the length of r odlike polar molecule). The orientational order parameter S of monolay ers and Maxwell displacement current (MDC) at the dielectric relaxatio n process were obtained, for the first time, with the consideration of xi and tau. On the basis of the analysis developed here, we examined the generation of MDC across 4-cyano-4'-5-alkyl-biphenyl (5CB) Langmui r film by monolayer compression.