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Self‐Association of Bis‐Dendritic Organogelators: The Effect of Dendritic Architecture on Multivalent Cooperative Interactions
Author(s) -
Seo Myungeun,
Kim Jung Hak,
Kim Jisung,
Park Nojin,
Park Jeyoung,
Kim Sang Youl
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902575
Subject(s) - dendrimer , benzamide , chemistry , alkyl , supramolecular chemistry , molecule , stacking , intermolecular force , hydrogen bond , hydrophobic effect , crystallography , stereochemistry , polymer chemistry , organic chemistry
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. π–π 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.