Novel columnar liquid crystalline oligomers: Triphenylene tetramers with rigid aromatic Schiff-bases and hydrogen-bonding spacers via click chemistry

Three novel triphenylene tetramers with triazole bridges, rigid aromatic Schiff-bases and hydrogen-bonding spacers were designed and synthesized in yield of 73-78%. Their structures were confirmed by IR, NMR and MS. Their mesomorphic properties were studied by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. These novel triphenylene tetramers possessed the hexagonal columnar mesophase and exhibited excellent mesomorphic properties with melting points at 30-60 °C, which was first observed near room temperature for triphenylene tetramers. This study suggested that the mesomorphic properties of triphenylene oligomers could be tuned conveniently by the structures of spacers.