Alignment and phase transition induced by surface action in lyotropic nematic liquid crystals

The alignment properties of lyotropic nematic liquid crystals (LNLC) on treated substrates were studied. Hydrophobic vs hydrophilic surfaces as well as rubbed vs nonrubbed surfaces were used to investigate the influence of the boundary surfaces on the spontaneous alignment of LNLC. It was found that the nematic particles can follow the anchoring direction imposed by the surface only when the LNLC material is strongly confined. We also observed a phase transition induced by surface action in the case of strong confinement. The reorientation and relaxation processes of the nematic director at the treated boundary surfaces were also studied. The characteristic times of these processes were found to be dependent on the sample thickness and the surface properties.