Nematic liquid crystal in the wedge and edge geometry in the case of homeotropic alignment
Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland
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Revised: 16 December 2009
Published online: 1 March 2010
Nematic liquid crystal confined to a wedge or edge is studied on the assumption that the confining surfaces provide strong and weak homeotropic anchorings, respectively. Both infinite and finite systems are considered. The model based on the Frank-Oseen and Rapini-Papoular formalisms predicts two textures of opposite rotations of the director as in the case of strong anchoring on both surfaces. However, the presence of weak anchoring results in a length scale λ which characterizes the crossover between the regions close to the apex and far from it. The ratio λ/b , where b is the extrapolation length, is a function of the opening angle α. Both stable and metastable textures are considered and the mechanism by which a texture loses its stability is found. It is related to the formation of a defect-like structure at the surface of weak anchoring whose distance from the apex is λ(α) and the loss of stability is signalled by the divergence of λ. Only in the limit α → 2τ, the defect-like structure transforms into a defect of strength -1/2 located at a finite distance from the apex.
© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg, 2010