Alignment of nematic liquid crystals on mixed Langmuir-Blodgett monolayers

Monolayers of stearic and behenic acids and mixtures of them in different proportions, deposited with the Langmuir-Blodgett (LB) technique, were used to study the alignment and the alignment dynamics in nematic liquid crystal cells. A relaxation process from a splay-bend how-induced metastable orientation to the homeotropic one occurs. The lifetime of the metastable state was found to depend on the monolayer composition. The transition between the homeotropic and the conical anchoring was found to be irreversible in the case of the mixed aligning monolayers: on cooling from the isotropic phase a quasi-planar nematic state (schlieren texture) appears. It is stable in a range of a few degrees below the clearing point and, on decreasing the temperature, relaxes to the homeotropic state in the form of expanding domains. (C) 1998 Elsevier Science S.A. All rights reserved.