Critical Behaviour of a Nematic-Liquid-Crystal Anchoring at a Monostable-Bistable Surface Transition

We study the 5CB nematic-liquid-crystal anchoring properties of a grazing SiO evaporated amorphous substrate, under the reorienting action of an electric field normal to the surface. Due to the low surface symmetry an anchoring anisotropy A can be defined. At constant temperature, by varying the evaporation parameters, we observe the critical behaviour of the anchoring strength W loc and the surface anisotropy A close to a planar monostable → bistable transition. We measure a W loc which goes to zero and an A which is maximum at the surface transition.