Synthesis and mesomorphic properties of two series of new azine-type liquid crystals

Two series of symmetrical azine-type liquid crystals were synthesised and their chemical structures identified by FTIR, H-1 NMR and elemental analysis. Their mesomorphic properties were investigated by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. The characteristic of these liquid crystals is that they have a high clearing point ( most were higher than 320 degrees C) and a broad thermal range in the mesophase. The end groups of the liquid crystals had an effect on their mesomorphic properties. The series with alkoxy end groups all exhibited both smectic A (SmA) and a nematic phase, whereas the series with alkyl end groups showed only nematic phase at their lower analogues and showed both SmA and nematic properties at their higher analogues.