Orientational Behavior of Discotic Nematic Phase for a Discotic Liquid Crystalline Triphenylene on Polyimide and Alkylammoniumbromide Coated Substrates

Abstract Orientational behavior of a discotic liquid crystalline triphenylene (C8OBT) on the substrates coated with a polyimide and a cetyltrimethylammoniumbromide (CTAB) was investigated by polarizing microscopy. The averaged direction and the order parameters of the triphenylene core plane and carbonyl groups of C8OBT were evaluated by an infrared dichroic method. C8OBT exhibits a homeotropic alignment on a polyimide film as for the discotic nematic (ND) phase, while it shows a tilt or homogeneous alignment on a CTAB-coated substrate. The order parameter of triphenylene ND phase is higher on the polyimide (S = 0.6) than a CTAB-coated substrate (0.2), in contrast to that of the carbonyl groups is comparable (0.2).