Structure-property relationships in non-conventional liquid crystalline materials
The aim of this thesis is to investigate structure-property relationships in several types of non-conventional liquid crystalline materials. First, supramolecular hydrogen bonded complexes involving either acid or phenol-based donors with pyridyl-based acceptors were studied using FT-IRM. These studies were made to investigate the nature and temperature dependence of the hydrogen bond between the donor and acceptor moieties. Second, a study of carbohydrate liquid crystals was undertaken. In this investigation two different types of carbohydrate-based materials were synthesised; (a) a homologous series of mono-tailed carbohydrates, the methyl-6-O-(n-acyl)-a-D-glucopyranosides were prepared to study the effect of alkyl chain length on phase behaviour and to elucidate how stereochemistry and the position of the alkyl chain affects liquid crystallinity; (b) a novel non-symmetric dimer containing a methoxyazobenzene moiety and a carbohydrate headgroup to study the behaviour of a dimer consisting of two incompatible mesogenic groups. Third, the effect of terminal alkyl chain branching on the molecular organisation in the intercalated smectic. A phase, was studied with a view to exploring the nature of the driving force for smectic phase formation in symmetric and non-symmetric liquid crystal dimers. The symmetric dimer chosen was 4.060.4, while the non-symmetric dimer was CB.060.4. In both systems the n-butyl terminal chains were replaced by either sec-butyl or tert-butyl chains. To establish how these structural changes effect smectic phase formation, binary phase diagrams of n-butyl-based compound with the corresponding branched material have been constructed. Finally, a comparison of the mesogenic properties of a series of monomers, dimers and side-chain liquid crystal polymers containing a methoxyazobenzene mesogenic unit was made. There data were used to examine the virtual trimer model as a means of rationalising the mesogenic behaviour of the polymers.