Preparation of liquid crystals containing Azobenzene and Alkyl Chains as terminal group

Liquid crystals have long dominated in the display devices, due to their large optical anisotropies and ability to undergo electric-field induced switching. In particular, liquid crystals containing azobenzene offers faster switching times than electric-field induced switching. The synthesis of liquid crystals containing azobenzene and alkyl chains as terminal groups is studied. The target compounds of ethyl-4-{ 4- hexyloxyphenylazo )benzoate (compound 2), ethyl-4-{ 4-decyloxyphenylazo )benzoate (compound 3), and ethyl-4-(4-hexadecyloxyphenylazo)benzoate (compound 4) were prepared. These liquid crystals were prepared through several organic syntheses steps which are diazonium coupling and Williamson ether synthesis reactions. The yield obtained for all the compounds synthesized was in the range 70-80010. Infrared spectroscopy was used to identify the functional groups of all the intermediates and target compounds. IH NMR spectroscopy was carried out only for compound 2 in order to confirm its molecular structure. The mesomorphic behaviours of the target compounds were investigated using differential scanning calorimetry (DSC). The DSC thermograms reveal that only compound 2 is a liquid crystalline molecule as it exhibited mesophase. As for compounds 3 and 4, they are crystalline solids because no mesophase was discovered. The transition temperatures of these compounds were influenced by different lengths ofthe alkyl chains