Journal of Surfactants and Detergents

, Volume 7, Issue 4, pp 387–395

The self-aggregation of sodium perfluorooctanoate in aqueous solution at different temperatures

  • Alfredo González-Pérez
  • Juan M. Ruso
  • Gerardo Prieto
  • Félix Sarmiento
Article

DOI: 10.1007/s11743-004-0323-9

Cite this article as:
González-Pérez, A., Ruso, J.M., Prieto, G. et al. J Surfact Deterg (2004) 7: 387. doi:10.1007/s11743-004-0323-9

Abstract

Electrical conductivities of sodium perfluorooctanoate (SPFO) in aqueous solutions were measured at different temperatures (range 294–328 K). Critical micelle concentrations (CMC) and the degree of ionization (α) of the micelles were derived from such data. The results revealed that temperature dependence of CMC is U-shaped with a minimum at 316 K. Gibbs free energies, enthalpies, and entropies of micelle formation as a function of temperature were estimated from the CMC and α values using the charged pseudo-phase separation model. To correlate the enthalpic and entropic contributions, the compensation phenomenon was studied, with a compensation temperature of 309 K and an intercept of −27.7 kJ·mol−1. Apparent molar volumes and adiabatic compressibilities of SPFO were determined from density and ultrasound velocity measurements in the same temperature range as conductivities. Positive deviation from the Debye-Hückel limiting law of the apparent molar volume in the range of temperatures studied evidenced hydrogen bonding-type interactions between monomers and the existence of dimers in the premicellar region. With micellization, the apparent molar volumes decrease with rising temperature, indicating that the structure of micelles is looser than that of monomers. The isentropic apparent molar adiabatic compressibilities following micellization were positive, indicating the predominant role of the decrease in hydrophobic hydration in the association process.

Key words

Apparent molar compressibilities apparent molar volumes conductivities critical micelle concentration perfluorooctanoate self-aggregation thermodynamics of self-aggregation 

Abbreviations

a

degree of ionization

CMC

critical micelle concentration

SPFO

sodium perfluorooctanoate

Copyright information

© AOCS 2004

Authors and Affiliations

  • Alfredo González-Pérez
    • 1
  • Juan M. Ruso
    • 1
  • Gerardo Prieto
    • 1
  • Félix Sarmiento
    • 1
  1. 1.Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of PhysicsUniversity of Santiago de CompostelaSantiago de CompostelaSpain

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