Liquid crystalline behaviour of hydrazide derivatives containing alkoxyazobenzene

Two series of dissymmetric hydrazide derivatives containing alkoxyazobenzene with nitro terminal group and octyloxy terminal group, N-4-alkoxyphenyl-N-4-((4-nitrophenyl)azophenyl) benzohydrazide (Bn-NO2, n indicates the number of carbon atoms) and N-4-octyloxyphenyl-N-4-((4-octyloxyphenyl)azophenyl) benzohydrazide (B8-B8), were designed and synthesised, and their liquid crystalline properties were investigated by means of differential scanning calorimetry, polarised optical microscopy and wide-angle X-ray diffraction. It was found that B8-B8 with octyloxy terminal chains displayed monolayer smectic C phase, whereas Bn-NO2 with nitro terminal group displayed SmA(d) phase, and intermolecular hydrogen bonding was confirmed as the driving force. In addition, the effect of hydrogen bonding, dipole-dipole interactions and steric hindrance effect on the liquid crystalline structures were also discussed.