THERMAL RELAXATION MODEL OF SURFACE DIRECTOR GLIDING IN LYOTROPIC LIQUID-CRYSTALS

The gliding of the nematic director at an isotropic surface in a lyotr opic liquid crystal, induced by a magnetic field, is theoretically ana lyzed by means of a thermal relaxation model. We formulate a master-eq uation describing the process and we derive a Fokker-Planck approximat ion from which simple analytical results are obtained. The relaxation time is found to be inversely proportional to the square of the magnet ic field, in agreement with recent experimental measurements. The obse rved temperature dependence of the relaxation time is explained in the framework of a simple mean-field model in which the surface energy is supposed to be proportional to the bulk nematic order parameter.