Density-functional theory of nematic and smectic-A order near surfaces

We present a density-functional theory for the growth of equilibrium nematic and smectic-A wetting layers near free surfaces. In the nematic case our theory predicts complete wetting, with the integrated order parameter diverging logarithmically as one approaches the ordering temperature from the isotropic phase. When a smectic phase is approached from the isotropic phase, we find a discrete series of metastable surface phases with integral numbers of layers of smectic order, and incomplete wetting with one or two first-order layering transitions among these surface phases. These results agree qualitatively with recent experiments.