Abstract
The orientational behavior of hexagonal columnar (Col_h) mesophase for the triphenylene compounds having fluoroalkylated side chains was investigated on the polyimide-, cetyltrimethylammonium bromide (CTAB) - and Indium-SnO_2 (ITO) - coated glass substrates by polarizing optical microscopy. It was found that 2, 3, 6, 7, 10, 11-hexakis (1H, 1H, 2H, 2H, 3H, 3H-perfluoroheptyloxy) triphenylene (F4) exhibits a spontaneous homeotropic alignment on all substrates, while the corresponding hydrocarbon mesogen does not. In Col_p mesophase of the non-fluorinated butyloxy derivative (C1) tends to show a planar alignment on all these substrates, while 4, 4, 4-trifluorobutyloxy derivative (F1) shows neither a homeotropic nor a planar alignment in Col_h, phase. These indicate that the homeotropic alignment of Col_h, phase for triphenylene mesogens could be easily attained by the introduction of an appropriate length of the fluoromethylene group into the peripheral chains.
