Liquid-crystal orientation induced by polymeric surfaces

Abstract

Orientation induced on liquid crystals by plane polymeric surfaces has been investigated. Thin polymerized films were prepared from hexamethyl disiloxane, methyl methacrylate, and isobutylene by a glow-discharge process; from γ glycidoxy-propyl-trimethoxy silane by dip coating; from polytetrafluoroethylene by sputtering. Critical surface tension γC of each film and surface tension γLV of various pure nematic compounds were measured, and orientation induced by the former on the latter was tested. When γC is very low, in front of γLV, very good homeotropic structure is observed. Conversely, high-energy surfaces seem to induce homogeneous structure.