Anchoring transition in confined discotic columnar liquid crystal films
Centre de Recherche Paul-Pascal, CNRS-Université de Bordeaux - 115 Avenue Schweitzer, 33600 Pessac, France, EU
Accepted: 22 December 2010
We report the achievement of ultrathin films (down to 25 nm thick) of thermotropic columnar liquid crystals in homeotropic alignment (columns normal to the interface) confined between a glass slide and a thin metallic electrode (about 150 nm thick). The face-on orientation of the discotic compound is obtained by anchoring transition of a columnar liquid crystalline phase from a degenerate planar orientation to the homeotropic alignment without any phase transition to the isotropic liquid phase. The kinetic dependence on temperature of such anchoring transition is investigated revealing various diffusive growth regimes of the homeotropic domains. Finally, confining effects are also considered by varying the thickness of the columnar liquid crystal film to reach the typical value required in organic solar cells thus demonstrating the reliability of such alignment process in a photovoltaic context.
PACS: 61.30.Hn – Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions / 64.70.mj – Experimental studies of liquid crystal transitions / 68.55.-a – Thin film structure and morphology
© EPLA, 2011