SUPRAMOLECULAR CHIRAL LIQUID-CRYSTALS - THE LIQUID-CRYSTALLINE BEHAVIOR OF MIXTURES OF 4,4'-BIPYRIDYL AND 4-[(S)-(-)-2-METHYLBUTOXY] BENZOIC-ACID

The thermal behaviour of binary mixtures of 4,4'-bipyridyl and 4-[(S)- (-)-2-methylbutoxy] benzoic acid has been investigated. The two compon ents are not liquid crystalline. By comparison, mixtures containing be tween 0.1 and 0.5 mole fraction of 4,4'-bipyridyl exhibit mesogenic be haviour; specifically, chiral nematic, blue and smectic A phases are o bserved. The induced mesogenic behaviour is attributed to the formatio n of elongated hydrogen bonded complexes and this view is supported by infrared spectroscopy. The crystal structure of the complex containin g 0.3 mole fraction of 4,4'-bipyridyl was determined using X-ray diffr action. This confirmed the formation of linear hydrogen bonded complex es in which two acid fragments are attached to a central 4,4'-bipyridy l core and supports the view that such complexes are responsible for t he liquid crystalline behaviour of these mixtures.