SURFACE-INDUCED ORIENTATIONAL ORDER IN THE ISOTROPIC-PHASE OF A LIQUID-CRYSTAL MATERIAL

Orientational order in the isotropic phase of liquid crystals confined to 0.2-mu-m-diam cylindrical channels of Anopore membranes is measured by deuterium nuclear magnetic resonance. At temperatures deep in the isotropic phase, the measurements reveal the order of the first molecular layer at the cavity wall, while at temperatures near the isotropic-nematic transition the measurements are primarily sensitive to order penetrating into the cavity in a manner described by the Landau-de Gennes theory. The degree of order S0 at the cavity wall is measured and the surface coupling constant determined for various treatments of the cavity wall. Wide variations of S0 are found for different surface treatments. Treatments that yield both perpendicular and parallel molecular anchoring are explored. The angular dependence of the surface-induced nematic order is investigated following the P2(cos-theta) expression independent of molecular anchoring at the surface.