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

The eigenmodes of director orientational fluctuations in nematic liquid crystals in confined geometries were studied both theoretically and experimentally by dynamic light-scattering tehnique. The fundamental mode of the orientational fluctuations shows a crossover from bulk behavior, dominated by bulk elastic constant K, to surface dominated one, in which the relaxation rate is determined by the ratio of surface anchoring strength W and viscosity eta. The contribution of surface viscosity zeta is also significant when its characteristic length zeta/eta becomes comparable to the size of the confined system. It was measured in nematic liquid crystal in cylindrical pores of polycarbonate (Nuclepore) membranes to be of the order of 10 nm.