Structure and transport properties of a charged spherical microemulsion system

Alex Evilevitch, Vladimir Lobaskin, Ulf Olsson, Per Linse, Peter Schurtenberger

Research output: Contribution to journalArticle

Abstract

Structure and transport properties of an oil-in-water microemulsion of weakly charged spherical micelles were studied experimentally using viscosity, NMR self-diffusion, and static and dynamic light scattering as well as theoretically by Brownian dynamics and Monte Carlo simulations and the Poisson-Boltzmann equation. The micelles contain decane covered by the nonionic surfactant pentaethylene glycol dodecyl ether (C12E5) and the ionic surfactant sodium dodecyl sulfate. The system has a constant surfactant-to-oil ratio, and the total volume fraction of surfactant and oil, Φ, is varied between 0.01 ≤ Φ ≤ 0.46. The micelles were made weakly charged by replacing a small fraction (0.01, 0.04, and 0.06) of the nonionic surfactant with ionic surfactant, retaining the micellar size. Comparison between self-diffusion and viscosity coefficients measured as a function of concentration showed that the system obeys the generalized Stokes-Einstein relation at lower micellar concentrations. At higher micellar concentrations, a slightly modified equation can be used upon the addition of an extra frictional factor due to stronger interactions. The collective diffusion coefficient shows a maximum as a function of the volume fraction. This result is in good agreement with predictions based on a charged hard-sphere model with hydrodynamic interactions. Other static and dynamic properties such as osmotic pressure, osmotic compressibility, and self-diffusion coefficient were obtained theoretically from simulations based on a charged-sphere model. The static and dynamic properties of the charged hard-sphere model qualitatively describe the behavior of the charged microemulsion micelles. At high volume fractions, Φ > 0.1, the agreement is quantitative, but at Φ < 0.1 the effect of the charge is smaller than what is predicted from the model.

Original languageEnglish (US)
Pages (from-to)1043-1053
Number of pages11
JournalLangmuir
Volume17
Issue number4
DOIs
StatePublished - Feb 20 2001
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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  • Cite this

    Evilevitch, A., Lobaskin, V., Olsson, U., Linse, P., & Schurtenberger, P. (2001). Structure and transport properties of a charged spherical microemulsion system. Langmuir, 17(4), 1043-1053. https://doi.org/10.1021/la0011883