SURFACE EFFECTS ON ORIENTATION OF LIQUID-CRYSTALS

Optical second harmonic generation (SHG) is now being used to measure the orientations of mesogens adsorbed at a variety of polar organic su rfaces (e.g. rubbed films of polyimides). For some surfaces, at least, these measurements can be used to predict the anchoring of bulk liqui d crystals. Few rules exist, however, to guide the design of surfaces for manipulation of the orientations of adsorbed mesogens (and thus bu lk anchoring). These rules are difficult to establish on surfaces as c omplicated as those of rubbed polymers. Self-assembled monolayers form ed from functionalized alkanethiols on semi-transparent films of gold and silver do permit the synthesis of well defined surfaces, and these surfaces are now being used in studies of the anchoring of liquid cry stals. Orientations of liquid crystals on these surfaces differ substa ntially from orientations observed in the past on surfaces formed from organosilanes. (C) Current Chemistry Ltd.