Masakatsu Ukon

Alignment behaviour of the discotic nematic phase of 2,3,6,7,10,11-hexa(4-n-octyloxybenzoyloxy)triphenylene on polyimide and cetyltrimethylammonium bromide coated substrates

The orientational behaviour of the nematic discotic phase of 2,3,6,7,10,11-hexa(4-n-octyloxybenzoyloxy)triphenylene (C8OBT) on substrates coated with a polyimide or cetyltrimethylammonium bromide (CTAB) was investigated by polarizing optical microscopy. The averaged order parameters and directions of the triphenylene core and the carbonyl groups of C8OBT were evaluated by an infrared dichroic method. The discotic nematic (ND) phase of C8OBT exhibits a homeotropic alignment on a polyimide film, a typical nematic schlieren texture on a glass substrate, and a tilted or planar homogeneous alignment on a CTAB-coated substrate. The order parameter of the triphenylene core is higher on a polyimide film (S = 0.6) than on a CTAB-coated substrate (S = 0.2), whereas that of the carbonyl groups remains roughly constant at 0.2 to 0.3 independent of the substrate for the ND phase.

Photopolymerization and Molecular Orientational Order of the Discotic Nematic Phase in 2,3,6,7,10,11-Hexakis(4-(8-acryloyloxyoctyloxy)benzoyloxy)triphenylene

A triphenylene-based discotic liquid crystal, 2,3,6,7,10,11-hexakis(4-(8-acryloyloxyoctyloxy)benzoyloxy)triphenylene (6ABTP) was investigated on the behavior of local order parameters for the discotic nematic (N D ) phase from the viewpoint of change of the molecular orientational order by photopolymerization. The local order parameters of the aromatic C = C, C-H and two C = O bonds of the acryloyl and benzoyl C = O groups were evaluated by an infrared dichroic method of Vij et al. It was found that 6ABTP tends to show a homeotropic alignement in the N D phase on a polyimide film spin-coated on BaF 2 and the triphenylene core shows a large order parameter (ca. 0.4-1.0), while the C = O moieties have a quite lower one (< 0.3). In order to investigate the disordering of molecular alignement due to crosslinking by photopolymerization, the behavior of local order parameters in photopolymerization was also evaluated. It was found that the order parameter of the aromatic core in the N D phase remarkably decreases at the early stage of photopolymerization, but only about 20% of decrease in the order parameter could be attained at the end of polymerization.

The positive effect on hole transport behaviour in anisotropic gels consisting of discotic liquid crystals and hydrogen-bonded fibres

The hole mobility of a discotic liquid-crystalline triphenylene compound is enhanced by the gelation with hydrogen-bonded fibrous aggregates.

Effect of Photopolymerization on Photoconductive Behavior in Triphenylene Discotic Liquid Crystals

Abstract Photoconductivity of the polymerized triphenylene film and monomer liquid crystal were evaluated for the nematic order. For the polymerized triphenylene film with a cross-linked network, which was derived from the monomers with six acrylate groups, the observed photocurrent was undetectable (<10−10A, 50kV·cm−1) though the monomer film before polymerization showed it in the detectable level. On the other hand, the photocurrent of the polymer film from the monomer with two acrylate groups was sufficiently detectable (>10−9A, 30kV·cm−1). Furthermore, the temperature range where the photocurrent is obtained was extended up to 200°C for the polymer film.

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).