Formation of columnar liquid crystals on the basis of unconventional triazine-based dendrimers by the C _3-symmetric approach

摘要

Two series of unconventional triazine-based dendrimers with C _2 symmetry and C _3 symmetry were prepared. The newly prepared C _3-symmetrical dendrimers were characterized by ~1H and ~(13)C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD showed that the C _3-symmetrical dendrimers display columnar liquid-crystalline phases during thermal treatment, but the C _2-symmetrical dendrimers were not observed to behave correspondingly. The molecular conformations of C _3- and C _2-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 C _3- and C _2-symmetric dendrimers. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks for displaying columnar liquid-crystalline behavior.