WETTING AND LAYERING TRANSITIONS IN LIQUID-CRYSTALS

Interfacial structure in the isotropic phase of a liquid-crystalline m aterial near a wall is studied by a mean-field density-functional theo ry. With increasing strength of the wall anchoring potential, the theo ry predicts a first-order transition from incomplete to complete wetti ng by the smectic-A phase at bulk isotropic-smectic coexistence, with an associated prewetting transition occurring away from bulk coexisten ce. The incomplete wetting case is accompanied by a small number (betw een 0 and 2) of,discrete layer transitions, while an infinite number o f such transitions occurs at complete wetting. An analysis of the unde rlying physical mechanisms for layer transitions reveals that these tr ansitions tend to disappear as the system is moved both sufficiently c lose to and sufficiently far from the bulk isotropic-nematic-smectic-A triple point by varying the model coupling parameters. These results reconcile findings from previous theories and experiments.