Effect of the incomplete interaction on the nematic-isotropic transition at the nematic-wall interface

摘要

The nematic-isotropic phase transition is investigated for a sample in the shape of a slab of thickness d, by means of a local self-consistent model. The effective interaction is written as the sum of the direct interaction of a given Dematic molecule with the substrate and of its incomplete interaction with the other nematic molecules due to the presence of the limiting surface. In the van der Waals approximation both contributions depends on the power -3 of the distance of the considered molecules from the substrate. In this framework we show the existence of a boundary layer in which the order parameter can be greater or smaller than the one in the bulk, according to the strength of the surface potential with respect to the nematic one. The model can provide a simple molecular framework to interpret characteristics of nematic liquid crystal confined in small-scale structures. (C) 2004 Elsevier B.V. All rights reserved.