SURFACE ELASTIC PROPERTIES OF NEMATIC LIQUID-CRYSTALS

The Maier-Saupe model is used to investigate the surface elastic prope rties of nematic liquid crystals. It is shown that in a surface layer, whose thickness is of the order of the interaction range of the molec ular forces responsible for the nematic phase, the elastic constants a re position dependent. The theoretical analysis shows that the usual e lastic constants reduce a factor two passing from the bulk to the surf ace and in the expression of the free energy density new elastic terms , arising from the presence of the bounding surface, have to be taken into account. Furthermore it is demonstrated that in the surface layer the splay and twist elastic constants behave in a different manner th an the bend elastic constant. The consequences on the modelization of the surface anchoring energy are also discussed. All the calculations are performed by supposing an interaction volume of spherical shape.