DYNAMIC BEHAVIOR AT A NEMATIC LIQUID-CRYSTAL RUBBED NYLON INTERFACE USING EVANESCENT-WAVE PHOTON-CORRELATION SPECTROSCOPY

Photon correlation spectroscopy of light scattered by director fluctua tions from an evanescent optical wave propagating in the nematic liqui d crystal 5CB is used to study the interfacial dynamic behaviour of th e liquid crystal. The intensity correlation function of light scattere d by interfacial orientation fluctuations is measured by illuminating to give a short optical penetration depth within the nematic. These su rface scattering correlation functions strongly differ from the bulk c orrelation function and are interpreted in terms of a nematic surface orientation mode arising from the coupling between the director field and the fluid velocity. It is shown that the analysis of the surface m ode gives a method for measuring anchoring energies in liquid crystals . The anchoring energy obtained for rotation of the director away from the rubbing direction about an axis normal to the surface for 5CB at a rubbed nylon surface is 7.14 +/- 0.7 x 10(-2) erg cm-2.