title: Self-association of bis-dendritic organogelators: the effect of dendritic architecture on multivalent cooperative interactions.
abstract: A series of bis-dendritic gelators consisting of a benzamide dendron and an alkyl dendron were synthesized to investigate the dendritic effect on self-assembly. The gelators with a first-generation benzamide (benzamide-G1) dendron or a first-generation alkyl (alkyl-G1) dendron formed stable gels in most aromatic solvents, and their self-assembled fibrillar networks were imaged by electron microscopy. The unbranched molecule (G0-G0) or the molecule possessing a second-generation benzamide (benzamide-G2) dendron did not form gels. Differential scanning calorimetry, powder X-ray diffraction, and Fourier transform IR studies revealed that introduction of a dendritic branch strongly affected the molecular packing as well as the strength of intermolecular interactions. Furthermore, concentration-dependent diffusion coefficient measurements and the evaluation of association constants by (1)H NMR spectroscopy indicated that bis-dendritic gelators with a benzamide-G1 dendron possessed high association constants and formed large aggregates, whereas molecules with a single benzamide formed dimers in chloroform. The formation of self-assembled fibrillar networks was driven by the multivalent and cooperative hydrogen bonding observed in the benzamide-G1 dendrons. Pi-pi stacking of aromatic groups and van der Waals interactions between alkyl chains also played roles in the self-assembly process, thus indicating that a spatial balance between two dendrons is important.
authors.affiliation: Department of Chemistry, KAIST, Gwahangno 335, Yuseong-gu, Daejeon 305-701, Korea.
authors.forename: Myungeun
authors.initials: M
authors.lastname: Seo
authors.forename: Jung Hak
authors.initials: JH
authors.lastname: Kim
authors.forename: Jisung
authors.initials: J
authors.lastname: Kim
authors.forename: Nojin
authors.initials: N
authors.lastname: Park
authors.forename: Jeyoung
authors.initials: J
authors.lastname: Park
authors.forename: Sang Youl
authors.initials: SY
authors.lastname: Kim