Effect of including extra phenylazo moiety on the mesophase behaviour of three-ring azo/ester molecules

Abstract

ABSTRACTFive homologous series of the four-ring 4-substituted phenylazo phenyl 4ʹ-(4ʹ-alkoxy phenylazo) benzoates (Ina–e) were prepared and their mesophase behaviour investigated by differential scanning calorimetry (DSC) and phases identified by polarised light microscopy (PLM). Compounds prepared were structurally characterised via infrared, 1H-NMR, mass spectroscopy, thermogravimetric and elemental analysis. Transition temperatures were first correlated with the alkoxy-chain length (n, that varies between 6, 8, 10, 14, and 16 carbons) within each homologous series, and again with the polarisability anisotropy (ΔαX) of the Ar-X bond, where X changes between CH3O, CH3, H, Br, and CN groups . Comparative studies were made to investigate the effect of introducing the extra phenyl azo moiety into the previously investigated three-ring compounds, 4-substituted phenyl 4′-(4″-alkoxyphenylazo) benzoates (IIna–e), 4-substituted phenylazo 4′-(4″- alkoxy phenyl) benzoates (IIIna–e), and 4-(4′-alkoxy phenylazo) phenyl 4″-substituted benzoates (IVna–e), each bear the same polar group, X, and the alkoxy group, n .