Alignment of liquid crystals on ultrathin organized molecular films

Liquid crystal (LC) alignment techniques based on various kinds of ultrathi n organized molecular films are reviewed. The mechanisms of LC alignment on the organized films are discussed. For the homeotropic alignment of LCs. t he main anchoring mechanism is due to the dipole-dipole interaction between polar groups of an aligning agent and LC molecules; while the homogeneous alignment is mainly attributed to the orientation of polymer chains or poly mer aggregates. An experimental system for an anchoring transition induced by a conformation change of aligning molecules is introduced. Finally, the AFM experimental observations on the rubbed polymer films, and its mechanis ms are summarized. (C) 1998 Elsevier Science Limited. All rights reserved.