Issue 7, 1997

Supramolecular dimeric liquid crystals. The liquid crystalline behaviour of mixtures ofα-(4-pyridyloxy)-ω -[4-(4-butylphenylazo)phenoxy]alkanes and 4-octyloxybenzoic acid

Abstract

The thermal behaviour of binary mixtures of 1-(4-pyridyloxy)-5-[4-(4-butylphenylazo)phenoxy]pentane (Bu-azo-5-Pyr) and 1-(4-pyridyloxy)-6-[4-(butylphenylazo)phenoxy]hexane (Bu-azo-6-Pyr) with 4-octyloxybenzoic acid is reported. Both systems are miscible over the complete composition range; this miscibility is attributed to the formation of a hydrogen bond between the unlike species, a view confirmed by IR spectroscopy. Bu-azo-5-Pyr and Bu-azo-6-Pyr do not exhibit liquid crystallinity but enhanced liquid crystal behaviour is observed for the mixtures with the acid. In particular, smectic A behaviour is injected into the phase diagrams of both systems. The clearing temperatures of the mixtures containing Bu-azo-6-Pyr are considerably higher than those for the analogous mixture containing Bu-azo-5-Pyr. In addition, the entropy change associated with the clearing transition for the equimolar mixture containing Bu-azo-6-Pyr is significantly higher than that for the analogous mixture containing Bu-azo-5-Pyr. These observations strongly suggest the formation of a supramolecular dimeric liquid crystal. For the Bu-azo-6-Pyr-based system the specific molecular interaction between the pyridyl and acid fragments has not only strongly enhanced the liquid crystalline behaviour but also increased the degree of molecular ordering.

Article information

Article type
Paper

J. Mater. Chem., 1997,7, 1163-1167

Supramolecular dimeric liquid crystals. The liquid crystalline behaviour of mixtures ofα-(4-pyridyloxy)-ω -[4-(4-butylphenylazo)phenoxy]alkanes and 4-octyloxybenzoic acid

M. J. Wallage and Corrie T. Imrie, J. Mater. Chem., 1997, 7, 1163 DOI: 10.1039/A700848A

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