Effect of orientation of lateral fluorine atom on the mesophase behaviour of azo/ester molecules with terminal naphthyl group.

Two homologous series of the three-ring 4ʹ-(4"-alkoxy-2"-(or 3")fluoro phenylazo) benzoates terminated with 2-(or 1-) naphthyl groups (Ind&e or IInd&e), respectively, were prepared and their mesophase behaviour investigated via differential scanning calorimetry, whereas the type of the mesophase identified by polarised light microscopy. Molecular structures of compounds prepared were first characterised via infrared, 1H-NMR and elemental analyses. Transition temperatures were correlated with the alkoxy chain length (n) that varies between 6, 8, 10, 12, 14 and 16 carbons. Comparative studies were made to investigate the effect of including the lateral fluorine atom, and its orientation, into the previously investigated fluorine-free analogues, namely, 2-(or 1-) naphthyl 4ʹ-(4"-alkoxyphenylazo) benzoates (Ina and IIna). The study was extended to investigate the effect of replacing the methyl group in the previously prepared 2"- and 3"-methyl analogues (Inb&c or IInb&c) with the fluorine atoms on their mesophase behaviour. [ABSTRACT FROM AUTHOR]