Formation of Columnar Liquid Crystals on the Basis of Unconventional Triazine-Based Dendrimers by the C3-Symmetric Approach

Two series of unconventional triazine-based dendrimers with C2 symmetry and C3 symmetry were prepared. The newly prepared C3-symmetrical dendrimers were characterized by 1H and 13C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD showed that the C3-symmetrical dendrimers display columnar liquid-crystalline phases during thermal treatment, but the C2-symmetrical dendrimers were not observed to behave correspondingly. The molecular conformations of C3- and C2-symmetrical dendrimers were obtained by computer simulation with the MM2 model of the CaChe program in the gas phase. The simulation results reasonably explain the different mesogenicities of C3- and C2-symmetric dendrimers. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks for displaying columnar liquid-crystalline behavior.