INTERFACIAL ENERGY FOR NEMATIC LIQUID-CRYSTALS - BEYOND THE SPHERICAL APPROXIMATION

By means of a simple pseudomolecular model the surface elastic properties of nematic liquid crystals are analysed. We show that in the Maier-Saupe approximation for the intermolecular interaction and supposing the interaction volume of ellipsoidal shape, the bulk elastic constants of splay and twist are expected to be equal and different from the bend one. The dependence of the bulk elastic constants on the eccentricity of the ellipsoid is studied. In the same framework it is shown that the number of phenomenological parameters necessary to describe the surface elastic behaviour of nematic liquid crystals is different from the one in the bulk. The position dependence of the surface elastic constants is evaluated and the anisotropic part of the surface tension is determined. The anchoring energy strength, in the Rapini-Papoular sense, versus the eccentricity of the ellipsoid representing the interaction volume is also estimated.