Modifying the structure and flow behaviour of aqueous montmorillonite suspensions with surfactant

Yannan Cui, Claire L. Pizzey, Jeroen S. van Duijneveldt*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

10 Citations (Scopus)

Abstract

Colloidal suspensions of plate-like particles undergo a variety of phase transitions. The predicted isotropic/nematic transition is often pre-empted by a sol/gel transition, especially in suspensions of the most commonly used natural swelling clay montmorillonite (MMT). A number of factors, including charge interactions, flexibility and salt concentration, may contribute to this competition. In this study, the effect of surfactant adsorption on suspensions of MMT was studied using rheology, small-angle X-ray scattering, static light scattering and optical microscopy. The addition of a polyetheramine surfactant reduced the moduli of the system and shifted the sol/gel transition to a much higher clay concentration, compared with suspensions of bare clay particles. Yet, scattering data revealed no change in suspension structure on length scales up to around a micrometre. Primary aggregates remain at this length scale and no nematic phase is formed. There is, however, a change in structure at large length scales (of order 20 mu m) where light scattering indicates the presence of string-like aggregates that disappear on addition of surfactant. Microscope images of dried suspensions also revealed a string-like structure. The dried strings show strong birefringence and may consist of concentric cylinders, self-assembled from clay sheets.

Original languageEnglish
Article numberARTN 20120262
Number of pages13
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Volume371
Issue number1988
DOIs
Publication statusPublished - 13 Apr 2013

Keywords

  • clay
  • NEMATIC PHASE-TRANSITION
  • PLATE-LIKE PARTICLES
  • COLLOIDAL PLATELETS
  • scattering
  • SOL-GEL TRANSITIONS
  • LIQUID-CRYSTAL PHASES
  • liquid crystal
  • NONAQUEOUS SUSPENSIONS
  • surfactant
  • ELECTROSTATIC INTERACTIONS
  • rheology
  • CLAY SUSPENSIONS
  • THIN HARD PLATELETS
  • CAPPED POLY(ETHYLENE OXIDES)

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