Hydrogen-bonded oxadiazole mesogens

Hydrogen-bonded analogues of recently reported biaxial nematic oxadiazoles have been prepared. These are obtained by having oxadiazole derivatized with either one or two pyridines, leading either to symmetric or unsymmetric materials complexed using several different benzoic acids. The new materials were studied by optical microscopy and DSC and were found to show N and SmA phases, i.e. mesomorphism characteristic of a calamitic rather than a bent-core mesogen. This mesomorphism is discussed in terms of the flexibility of the complexes and the bend angle at the centre of the complexes.