Star-Shaped Mesogens of Triazine-Based Dendrons and Dendrimers as Unconventional Columnar Liquid Crystals

Dendrons G n -Cl and G n -NH (n = 2−4) and novel dendrimers G n -N∼N-G n (n = 2−4) based on triazine and piperazine units were efficiently prepared in good yields without employing the protection and deprotection processes and are fully characterized by 1H NMR and 13C NMR spectroscopies, elemental analysis, and mass spectroscopy. These compounds are transparent and possess good thermal stability. G 4 -Cl shows a monotropic columnar phase in a narrow range with a coexisting crystalline phase. Dendron G 4 -NH shows a rectangular column-phase, and dendrimer G 4 -N∼N-G 4 exhibits a monotropic hexagonal columnar phase. These identifications were supported by the polarizing optical scope and powder XRD studies.