Modeling planar degenerate wetting and anchoring in nematic liquid crystalsJ.-B. Fournier1, 2 and P. Galatola1
1 Matière et Systèmes Complexes, UMR 7057 CNRS & Université Paris 7 2 place Jussieu, F-75251 Paris Cedex 05, France
2 Laboratoire de Physico-Chimie Théorique, UMR 7083 CNRS-ESPCI 10 rue Vauquelin, F-75231 Paris Cedex 05, France
received 17 June 2005; accepted 9 September 2005
published online 5 October 2005
We propose a simple surface potential favoring the planar degenerate anchoring of nematic liquid crystals, i.e., the tendency of the molecules to align parallel to one another along any direction parallel to the surface. We show that, at lowest order in the tensorial Landau-de Gennes order-parameter, fourth-order terms must be included. We analyze the anchoring and wetting properties of this surface potential. In the nematic phase, we find the desired degenerate planar anchoring, with positive scalar order-parameter and some surface biaxiality. In the isotropic phase, we find, in agreement with experiments, that the wetting layer may exhibit a uniaxial ordering with negative scalar order-parameter. For large enough anchoring strength, this negative ordering transits towards the planar degenerate state.
61.30.Hn - Surface phenomena: alignment, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions.
61.30.Dk - Continuum models and theories of liquid crystal structure.
64.70.Md - Transitions in liquid crystals.
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