Dynamic light scattering as a probe of orientational dynamics in confined liquid crystals

The eigenmodes of director orientational fluctuations in nematic liquid cry stals in confined geometries were studied both theoretically and experiment ally by dynamic light-scattering tehnique. The fundamental mode of the orie ntational fluctuations shows a crossover from bulk behavior, dominated by b ulk elastic constant K, to surface dominated one, in which the relaxation r ate is determined by the ratio of surface anchoring strength W and Viscosit y eta. The contribution of surface viscosity zeta is also significant when its characteristic length zeta/eta becomes comparable to the size of the co nfined system. It was measured in nematic liquid crystal in cylindrical por es of polycarbonate (Nuclepore) membranes to be of the order of 10 nm.