Structural origin of the thixotropic behavior of a class of metallosupramolecular gels

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

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

Complexation, between a ditopic ligand, consisting of a 2,6-bis-(1′-methylbenzimidazolyl)-4-oxypyridine moiety (O-Mebip) attached to either end of a penta(ethylene glycol) core, with transition metal and lanthanide ions, results in the formation of metallosupramolecular polymers, soluble in acetonitrile at high temperatures. Cooling the hot sol to room temperature causes phase separation and crystallization, and produces mechanically-strong gels, which exhibit a highly thixotropic behavior. Optical microscopy indicates that the gel morphology consists of spherulitic particles, which are easily broken by mechanical shear. Reproducible gel properties are produced when the gel is formed by cooling in a sonication bath, which produces a finely-divided globular morphology, and increases the modulus of the gels. Wide angle X-ray diffraction study shows that the crystalline structures of the gels are strongly dependent on the thermal history of gel formation and the nature of the metal ion. The gel properties are a result of the interactions between the colloidal particles produced by the phase separation and crystallization process. These interactions, which may reflect electrostatic forces and possibly metal-ligand binding, in addition to the usual van der Waals interactions, give rise to the formation of a network structure. The disruption of this network by mechanical shear, and its facile reformation when shear is removed, are the origin of the pronounced thixotropic behavior of the gels.

Original languageEnglish
Pages (from-to)7419-7431
Number of pages13
JournalTetrahedron
Volume63
Issue number31
DOIs
Publication statusPublished - 2007 Jul 30
Externally publishedYes

Fingerprint

Gels
Metals
Crystallization
Phase separation
Ions
Ligands
Cooling
Lanthanoid Series Elements
Rubiaceae
Sonication
Temperature
Ethylene Glycol
Electrostatic force
Polymethyl Methacrylate
Complexation
Static Electricity
Baths
X-Ray Diffraction
Optical microscopy
Transition metals

Keywords

  • Colloidal gel
  • Crystallization
  • Rheological
  • Supramolecular polymer

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry
  • Drug Discovery

Cite this

Structural origin of the thixotropic behavior of a class of metallosupramolecular gels. / Weng, Wengui; Jamieson, Alex M.; Rowan, Stuart J.

In: Tetrahedron, Vol. 63, No. 31, 30.07.2007, p. 7419-7431.

Research output: Contribution to journalArticle

Weng, Wengui ; Jamieson, Alex M. ; Rowan, Stuart J. / Structural origin of the thixotropic behavior of a class of metallosupramolecular gels. In: Tetrahedron. 2007 ; Vol. 63, No. 31. pp. 7419-7431.
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