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Influence of Micellar Microenvironments on Redox and Kinetic Properties of Radical Ions

  • Gregory L. McIntire
  • Henry N. Blount

Abstract

The effects of micellar microenvironments on the redox properties of solubilized substrates and on the kinetic properties of their corresponding radical ions have been examined in anionic, cationic, and nonionic surfactant systems. Relative to the value observed in the absence of surfactants, the differential pulse voltammetric peak potential for the monoelectronic oxidation of 10-methylphenothiazine (MPTH) to the cation radical (MPTH) is not significantly altered by the presence of either cationic CTAB or nonionic Brij-35 micellar systems. In anionic SDS media, however, the formal potential for the oxidation of MPTH is shifted to less anodic values with increasing SDS concentration up to the CMC of this surfactant. This behavior is indicative of preferential stabilization of the cation radical by the anionic dodecylsulfate (DS) monomer. Analysis of the voltammetric data provides definitive evidence for the formation of an associated species involving one MPTH and one DS. The formation constant for this associate is found to be 2.0 × 103 M −1. Electron spin resonance (ESR) spectra of MPTH in SDS media show that above the CMC, the MPTH/DS associate is an integral part of the micelle assembly. UV spectral data indicate that the site of residence of the cation radical is in the Stern region of the micellar phase. While cationic and non-ionic micelles are found to catalyze the hydrolysis of MPTH, SDS micelles retard this process due to the strong associative interaction between the cation radical and the anionic surfactant.

Keywords

Electron Spin Resonance Electron Spin Resonance Spectrum Cation Radical Kinetic Property Micellar Phase 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1982

Authors and Affiliations

  • Gregory L. McIntire
    • 1
  • Henry N. Blount
    • 1
  1. 1.Brown Chemical LaboratoryThe University of DelawareNewarkUSA

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