COLLECTIVE FLUCTUATIONS AND WETTING IN NEMATIC LIQUID-CRYSTALS

The role of wetting in the dynamics of collective orientational fluctu ations in confined nematic liquid crystals is examined by analyzing th e spectrum of normal modes in planar geometry bounded either by disord ering or ordering substrates. The heterophase nature of the equilibriu m configurations occurring in the vicinity of the nematic-isotropic ph ase transition gives rise to a localized slow mode, which corresponds to fluctuations of thickness of the (dis)ordered boundary layer and be comes soft if the wetting is complete. In addition, a few modes restri cted to the boundary layer-director modes in case of ordering substrat e, and biaxial modes in case of disordering substrate-also exhibit pre transitional slowdown provided that the surface interaction is strong enough. Analogous behavior of fluctuations is expected in other wettin g geometries, e.g., in the case of a substrate-stabilized smectic boun dary layer in nematic and isotropic samples.