Mesomorphic behaviour of new azomethine liquid crystals having terminal bromo substituent

A homologous series of azomethine esters, 4-n-alkanoyloxybenzylidene-4′-bromoanilines possessing even number of carbon atoms at the terminal alkanoyloxy chain (Cn-1H2n-1COO-, n = 8, 10, 12, 14, 16, 18) was synthesized and characterized. Whilst n-octanoyloxy to n-dodecanoyloxy derivatives exhibited enantiotropic smectic A and smectic B phases, n-tetradecanoyloxy to n-octadecanoyloxy derivatives possessed enantiotropic smectic A and monotropic smectic B properties. n-Decanoyloxy derivatives demonstrated the optimum exhibition for both smectic A and smectic B phases. It was found that the length of terminal alkanoyloxy chain has an influence on mesomorphic properties.