Surface tensions and anchoring transitions of nematic liquid crystals on gradually oxidized substrates

Abstract

Intermediate anchorings of nematic liquid crystals onto substrates are now intensively studied essentially because of their potential display applications. Here, we use the active oxygen gas arising from a plasma reactor to realize progressive chemical modifications of glass substrates covered with silane. In this manner, the dispersive and nondispersive surface tensions of the substrate are gradually modified involving a continuous change in the differential wetting properties of the substrate with both parts of the liquid crystal molecules, and in the anchoring energy. Intermediate anchorings with tilted angles are thus obtained in the vicinity of an anchoring transition from the pseudohomeotropic to the planar alignment, where symmetry is broken.