Non-symmetric liquid crystal dimers containing the 4-nitrobenzohydrazide group: synthesis and mesomorphic behaviour

The synthesis and mesomorphic behaviour are reported of a new series of dimers containing 4-nitrobenzohydrazide and azobenzene groups as the mesogenic units. These non-symmetric liquid crystal dimers are found to exhibit a monolayer smectic A phase (SmA(1)). Lateral hydrogen bonding and strong dipole-dipole interactions are shown to be the major driving forces for the formation of the SmA1 phase. The present study indicates that the intermolecular interactions and thus the mesophase morphology of the liquid crystal dimers can be controlled by the appropriate selection of the molecular fragments capable of forming H-bonds.