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Electrostatic Charging of Nonpolar Colloids by Reverse Micelles

Research output: Contribution to journalArticle

  • Gregory Seth Roberts
  • Rodrigo Sanchez
  • Roger Kemp
  • Tiffany Wood
  • Paul Bartlett

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Original languageEnglish
Pages (from-to)6530-6541
Number of pages11
Publication statusPublished - 6 Jul 2008


Colloids dispersed in a nonpolar solvent become charged when reverse micelles are added. We study the charge
of individual sterically stabilized poly(methyl methacrylate) spheres dispersed in micellar solutions of the surfactants
sodium bis(2-ethyl 1-hexyl) sulfosuccinate [AOT], zirconyl 2-ethyl hexanoate [Zr(Oct)2], and a copolymer of poly(12-
hydroxystearic acid)-poly(methyl methacrylate) [PHSA-PMMA]. Although the sign of the particle charge is positive
for Zr(Oct)2, negative for AOT, and essentially neutral for PHSA-PMMA, the different micellar systems display a
number of common features. In particular, we demonstrate that over a wide range of concentrations the particle
potential is a constant, independent of the number of micelles added and independent of the colloid size. A simple
thermodynamic model, in which the particle charge is generated by the competitive adsorption of both positive and
negative micelles, is in good agreement with the experimental data.

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