Europhys. Lett.
Volume 76, Number 2, October 2006
Page(s) 243 - 249
Section Condensed matter: structural, mechanical and thermal properties
Published online 22 September 2006
Europhys. Lett., 76 (2), pp. 243-249 (2006)
DOI: 10.1209/epl/i2006-10248-8

Bistable anchoring of nematics on rough substrates

F. Schmid1 and D. Cheung2

1  Fakultät für Physik, Universität Bielefeld - D-33615 Bielefeld, Germany
2  Department of Physics, University of Warwick - Coventry, CV4 7AL, UK

received 3 April 2006; accepted in final form 18 August 2006
published online 22 September 2006

We analyze the interplay between wetting and anchoring of nematic liquid crystals on disordering, e.g., rough substrates in the framework of the Landau-de Gennes theory, in situations of competing homeotropic and planar easy axes on the substrate and the nematic-isotropic (NI) interface. The phase diagram for azimuthally symmetric substrates is calculated. We identify two regimes -a strongly coupled regime, where the wetting transition coincides with an anchoring transition, and a weakly coupled regime, where the two are separated. The anchoring transition is first order and switches between homeotropic and planar anchoring. The two competing orientations are metastable over a broad parameter range. Hence such surfaces can be used to generate bistable surfaces.

61.30.Dk - Continuum models and theories of liquid crystal structure.
61.30.Hn - Liquid crystals: Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions.
68.08.Bc - Wetting.

© EDP Sciences 2006