The stability of columns comprising alternating triphenylene and hexaphenyltriphenylene molecules: variations in the structure of the hexaphenyltriphenylene component

• Published in: Liquid crystals Vol. 33; no. 6; pp. 653 - 664
• Main Authors: Bushby, Richard J., Fisher, Julie, Lozman, Owen R., Lange, Stephan, Lydon, John E., McLaren, Sholto R.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 01.06.2006
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/02678290600682078

Previous investigations of complementary polytopic interaction (CPI) columnar mesophases, in which the columns are built up of alternating hexaalkoxytriphenylene (HAT) and hexaphenyltriphenylene (PTP) molecules, concentrated mainly on the effect of variations in the structure of the HAT component. This investigation is concerned with the effect of variations in the structure of the PTP component and, in particular, variations in the position of an alkoxy side chain in the phenyl ring. Stable columnar mesophases are obtained when a hexyloxy substituent is placed in the meta- or para-position but not in the ortho-position. In the case of the meta- and para-substituted systems, the two-component CPI columnar phases are stable over a considerably larger temperature range than the one-component HAT systems. The evidence suggests that unfavourable PTP/PTP stacking is as much a driving force for the formation of these mixed stacks as is favourable PTP/HAT stacking, but both need to be explained in terms of the sum of atomically dispersed van der Waals and coulombic interactions. On cooling from the isotropic into the Col h phase, the columnar phase based on a 1:1 mixture of hexakis(hexyloxy)tripenylene and the meta-hexyloxy-substituted PTP gives an unusual texture consisting of 'viking-axe'-shaped structures.