Synthesis of disk-rod-disk liquid crystal trimers by using click chemistry

A series of disk-rod-disk liquid crystal trimers were synthesized. CuI-NEt3 catalyzed alkyne azide cycloaddition in toluene at room temperature connected two triphenylene discogens to a biphenyl rod-shaped mesogen. The trimers were characterized by using H-1 NMR, IR, and high resolution mass spectrometry. The mesomorphic properties were investigated using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction. The results showed that the trimers exhibited rectangular columnar mesophase (Col(r)). The length of the flexible spacer connecting the three segments has prominent influence on the phase transition temperatures of the trimers.