Studies of Some Heterocyclic Mesogens

Abstract New mesogens have been prepared and studied by differential thermal analysis and optical microscopy to elucidate the effects on mesomorphic properties of replacing a benzene ring by differnt hiterocyclic rings. Earlier workers have assessed the effects on nematic properties arising from such changes in the terminal groups of molecules of the type 4-MeO.C6H4.C6H4.N:CH.R4 (where R is phenyl, pyridyl or certain five-membered heterocylic rings). By studying, the corresponding n-octyl ethers, the relative effects of the different terminal rings on smectic properties have now been established. The compounds exhibit smectic polymorphism and the types of phase have been examined. Compounds of the type 4-R.CH:N.C6H4-C6H4-N:CH-R-4′ showed some differences in trends compared with those for compounds with only one terminal group, R. Other compounds, including two series of the type 4-X'C6H4-CO-O-C6H4-CH:CH.R-4′ (where X is methoxy or n-octyloxy and R is phenyl, pyridyl or diazinyl), have been examined and sh...