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

Abstract

Dendrons Gn-Cl and Gn-NH (n = 2-4) and novel dendrimers Gn-N approximately N-Gn (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. G4-Cl shows a monotropic columnar phase in a narrow range with a coexisting crystalline phase. Dendron G4-NH shows a rectangular column-phase, and dendrimer G4-N approximately N-G4 exhibits a monotropic hexagonal columnar phase. These identifications were supported by the polarizing optical scope and powder XRD studies.

Design of a Peripheral Building Block for H-Bonded Dendritic Frameworks and Analysis of the Void Space in the Bulk Dendrimers

“…The dendrons with tert -butyl amide groups on peripheral benzene were prepared according to our previous procedure (Figure S1) 71–76 . Dendrimers ( t - Bu - G 2 N ) 2 , CC ( t - Bu - G 1 N ) 3 and ( t - Bu - G 1 N ) 2 were synthesized as summarized in Fig.…”

“…t - Bu - G n Cl (1 mmol; n = 1 or 2) and t - Bu - G n NH (1 mmol; n = 1 or 2), prepared according to our previous procedure 71–75 , were dissolved in dry THF (20 mL) in a sealed tube. Potassium carbonate (0.5 g, 5 mmol) was then added and sealed.…”

Advances in Metal‐Free Heterocycle‐Based Columnar Liquid Crystals

“…The approach by Li and co-workers to the step-economic synthesis of triazine-based dendrons and dendrimers. [46] line phase, R 4 -NH shows a rectangular columnar phase, and dendrimer R 4 -N~N-R 4 exhibits monotropic hexagonal columnar phase. Geometrically optimized structures of both R 4 -Cl and R 4 -NH showed an elliptical shape; however, their phase behaviors are different.…”

“…Li and co-workers reported the step-economic synthesis of triazine-based dendrons and dendrimers in high yields. [46] This synthetic strategy is very interesting as it did not involve any protection or de-protection steps. Addition of diluted dioctylamine (in CH 2 Cl 2 ) to the diluted solution of cyanuric chloride (in CH 2 Cl 2 ) in the presence of triethylamine under ice-cold condition followed by stirring the reaction mixture at 258C for 24 h furnished the disubstituted triazine chloride (R 1 -Cl) 16 a (Scheme 8).…”

Trimesic Acid-Based Star Mesogens with Flexible Spacer: Synthesis and Mesophase Characterization

“…[10,11] However, the recent upsurge has been more on non-conventional mesogens which essentially deviate from a rod-like or disk-like shape and have molecular shapes like V or bent-core, [12] T, [13] H, [14] l, [15] AE, [16] c, [17] and dendrimers. [18,19] Among the nonconventional liquid crystals, star mesogens have drawn considerable attention in view of their structural similarity with dendrimers. [20,21] Moreover, the C 3 symmetry of these molecular systems provides greater opportunity to investigate their shape dependent properties in the mesophase.…”