Novel discotic liquid crystal oligomers: 1,3,5-triazine-based triphenylene dimer and trimer with wide mesophase

Series of novel 1,3,5-triazine-based triphenylene oligomers 7, 10 and 12 with large bridging polyaromatic core were designed and synthesised by simple procedures in high yields. Their structures were confirmed by FTIR, 1H NMR, ESI-MS and elemental analyses. Their mesomorphic behaviours were studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. 1,3,5-triazine-based triphenylene monomer 7 has no mesomorphic property, but 1,3,5-triazine-based triphenylene dimer 10 and 1,3,5-triazine-based triphenylene trimer 12 possess excellent mesomorphic properties. The mesomorphic temperature range of compound 12 was as wide as 180°C. These studies indicated that the mesomorphic properties were determined by the numbers of triphenylene units. More units of triphenylene in the oligomers resulted in better mesomorphic properties.