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 degrees 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. (C) 2017 Elsevier B.V. All rights reserved.