Supramolecular self-assembly of dimeric dendrons with aromatic bridge units

The dimeric dendrons with amide branch units, alkyl periphery, and the aromatic bridging units such as naphthyl, biphenyl, or isopropylidenebiphenyl were synthesized via a convergent method. The self-assembly characteristics of these dimeric dendrons were investigated not only in organic media but also at the solid-liquid interface. The gel formation behavior of the dimeric dendrons in organic media and their nanostructures were highly dependent on the bridging moiety. The dendrons with naphthyl and biphenyl bridges form immobile gel in organic media such as n-octanol, while those with isopropylidenebiphenyl unit did not form gel. The dry gel obtained via self-assembly formed either lamellae or columnar hexagonal arrays depending on the structure of the bridge moiety. The dendron dimer with the 1,5-naphthoxy bridging unit which formed a lamella structure in a dry gel state also self-assembled at the solid-liquid interface in 0.1% n-octanol solution to exhibit well-defined nanoribbons extending to several micrometers. In addition to hydrogen bonding of the dendritic branches and van der Waals interactions of the alkyl periphery, the architecture of the bridging moiety of the dimeric dendrons played a key role in the packing process of the self-assembly of dimeric dendron.