Understanding the Mechanism of Gelation and Stimuli-Responsive Nature of a Class of Metallo-Supramolecular Gels
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 (...
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Published in | Journal of the American Chemical Society Vol. 128; no. 35; pp. 11663 - 11672 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Washington, DC
American Chemical Society
06.09.2006
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Subjects | |
Online Access | Get full text |
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Summary: | 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. |
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Bibliography: | istex:5D4971896AE1150AEE5CEB4E1987B47593AD3004 ark:/67375/TPS-XLST23LD-W ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0002-7863 1520-5126 |
DOI: | 10.1021/ja063408q |