Investigation of the structure/property relationships in triphenylene discotic liquid crystals
This thesis presents a detailed investigation of the relationship that exists between the molecular structure and the mesomorphic behaviour in discotic liquid crystals. This was achieved by the systematic alteration of the molecular architecture of one class of discotic liquid crystals - the triphenylen-2,3,6,7,10,11-hexayl hexakis(4-alkoxybenzoate)s which were first studied in 1981. It was shown, by the systematic increase in the lateral substituents (from hydrogen through to tert-butyl, both mono- and di-substituted) in both the outer and inner regions of the peripheral phenyl rings of these triphenylene benzoates, that both the position and size of the substituents greatly affect the melting points, transition temperatures and phase morphology. Studies on lateral substitution were also conducted using polar units and these results were equally remarkable. Examination of the effects of lengthening the peripheral arms, without lateral substituents of the triphenylene benzoates was also performed and with the results obtained, it allowed at last, the construction of a complete theoretical model for the relationship that exists between the molecular structure of discotic liquid crystals and the mesophase behaviour.