Electrostatic Charging of Nonpolar Colloids by Reverse Micelles

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

Research output: Contribution to journalArticlepeer-review

Abstract

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.
Original languageEnglish
Pages (from-to)6530-6541
Number of pages11
JournalLangmuir
Volume24
DOIs
Publication statusPublished - 6 Jul 2008

Keywords

  • CHARGE
  • Colloid
  • MICELLES
  • OPTICAL TWEEZERS

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