Understanding the mechanism of gelation and stimuli-responsive nature of a class of metallo-supramolecular gels

Wengui Weng, J. Benjamin Beck, Alex M. Jamieson, Stuart J. Rowan

Research output: Contribution to journalArticle

416 Citations (Scopus)

Abstract

Utilizing metal-ligand binding as the driving force for self-assembly of a ditopic ligand, which consists of a 2,6-bis-(1′-methylbenzimidazolyl)-4- oxypyridine moiety attached to either end of a penta(ethylene glycol) core, in the presence of a transition metal ion (ZnII) and a lanthanide metal ion (LaIII), we have achieved formation of stimuli-responsive metallo-supramolecular gels. We describe herein a series of experimental studies, including optical and confocal microscopy, dynamic light scattering, wide-angle X-ray diffraction, and rheology, to explore the properties of such gels, as well as the nature of the gelation mechanism. Morphological and X-ray diffraction observations suggest gelation occurs via the flocculation of semicrystalline colloidal particles, which results in the gels exhibiting pronounced yielding and thixotropic behavior. Application of mechanical stress results in a decrease in the particle size, which is accompanied by an increase in gel strength after removal of the stress. Moreover, studies show that the presence of lanthanide(III) perchlorate increases the mechano-responsiveness of the gels, as a consequence of reduced crystallinity of the colloidal particles, presumably due to the different coordination ability of lanthanide(III) and zinc(II), which changes the nature of the self-assembly in these materials.

Original languageEnglish
Pages (from-to)11663-11672
Number of pages10
JournalJournal of the American Chemical Society
Volume128
Issue number35
DOIs
Publication statusPublished - 2006 Sep 6
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)

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