  The anchoring of nematic liquid crystals on surfaces with grafted liquid
crystalline chain molecules is studied by computer simulations and within a
mean field approach. The computer simulations show that a swollen layer of
collectively tilted chains may induce untilted homeotropic (perpendicular)
alignment in the nematic fluid. The results can be understood within a simple
theoretical model. The anchoring on a layer of mutually attractive chains is
determined by the structure of the interface between the layer of chain
molecules and the solvent. It is controlled by an interplay between the
attractive chain interactions, the translational entropy of the solvent and its
elasticity. A second order anchoring transition driven by the grafting density
from tilted to homeotropic alignment is predicted.
