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Soft Matter and Biological Physics
Eur. Phys. J. E 10, 163-170 (2003)
DOI: 10.1140/epje/e2003-00020-3

Orientational phase transition and the solvation force in a nematic liquid crystal confined between inhomogeneous substrates

S. Kondrat1, A. Poniewierski1 and L. Harnau2, 3

1  Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
2  Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany
3  Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany

(Received 12 November 2002 Published online: 16 April 2003 )

A nematic liquid crystal confined between two identical flat solid substrates, with an alternating stripe pattern of planar and homeotropic anchoring, is studied in the framework of the Frank-Oseen theory. By means of numerical minimization of the free energy functional we study the effect of the sample thickness  D on the location of the phase transition between a uniform alignment, either planar or homeotropic, and a distorted nematic texture. The solvation force f due to distortions of the nematic director is also studied. It is found that f is always attractive, and for D small compared to the periodicity of the surface structure it exhibits two distinct asymptotic behaviors: $f\sim -D^{-1/2}$ or $f\sim -D^{-1}$, depending on the relation between  D and the extrapolation lengths.

64.70.Md - Transitions in liquid crystals.
61.30.Cz - Molecular and microscopic models and theories of liquid crystal structure.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003