Mesomorphic studies of novel azomesogens having a benzothiazole core: Synthesis and characterisation

Novel liquid crystals, including 2-[4-(4-n-alkoxybenzoyloxy)phenylazo]-6-fluorobenzothiazoles (Series E) and 2-[4-(4-n-alkoxybenzoyloxy)naphtha-1-ylazo]-6-fluorobenzothiazoles (Series F), have been synthesised and characterised. Each series contains 13 homologous members differing by the length of the alkoxy chain. In series E the derivative with C-1 to C-7 chain length were found to exhibit enantiotropic smectic C (SmC) and nematic (N) mesophases. The C-8 homologue possessed enantiotropic SmC, smectic A (SmA) and N mesophases, while the longer chain homologues (C-10 to C-14) showed enantiotropic SmC and SmA mesophases. The C-16 and C-18 homologues possessed only SmA mesophases. In Series F all the compounds (C-1 to C-18) exhibited only the enantiotropic nematic mesophase.