SURFACE TREATMENTS FOR LYOTROPIC LIQUID CRYSTALS ALIGNMENT

For nematic lyotropic liquid crystals it has been experimentally observed that in nontreated glass cells the director in the surface layer can be reoriented by a magnetic field in any direction parallel to the surface, and the filial state is stable. In this paper we will focus on the equilibrium configuration of the director in the surface layer in the presence of a magnetic field, using cells with treated surfaces to introduce an easy axis. ne surface treatments employed in this study are: rubbing of glass plates coated with polymer (PMMA), rubbing of bare glass plates, and unidirectional deposition of Teflon. All these surface treatments induce a preferential orientation to the liquid crystal. From AFM analysis we observe microchannels in the polymer films that are more homogeneous for the Teflon film. The experimental results indicate that the anchoring energy depends on the surface treatment and is larger for the rubbed glass plates.