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Issue 48, 2015
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Influence of additives on the structure of surfactant-free microemulsions

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Abstract

We study the addition of electrolytes to surfactant-free microemulsions in the domain where polydisperse pre-Ouzo aggregates are present. As in previous studies, the microemulsion is the ternary system water/ethanol/1-octanol, where ethanol acts as co-solvent. Addition of electrolytes modifies the static X-ray and neutron scattering, and dynamic light scattering patterns, as well as the position of the miscibility gap, where spontaneous emulsification occurs upon dilution with water. All observations can be rationalized considering that electrolytes are either “salting out” the ethanol, which is the main component of the interface stabilizing the aggregates, or producing charge separation via the antagonistic ion effect discovered by Onuki et al. Amphiphilic electrolytes, such as sodium dodecylsulfate or sodium dietheylhexylphosphate, induce a gradual transition towards monodisperse ionic micelles with their characteristic broad scattering “peak”. In these micelles the ethanol plays then the role of a cosurfactant. Dynamic light scattering can only be understood by combination of fluctuations of aggregate concentration due to the vicinity of a critical point and in-out fluctuations of ethanol.

Graphical abstract: Influence of additives on the structure of surfactant-free microemulsions

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Supplementary files

Article information


Submitted
20 Oct 2015
Accepted
18 Nov 2015
First published
18 Nov 2015

This article is Open Access

Phys. Chem. Chem. Phys., 2015,17, 32528-32538
Article type
Paper
Author version available

Influence of additives on the structure of surfactant-free microemulsions

J. Marcus, D. Touraud, S. Prévost, O. Diat, T. Zemb and W. Kunz, Phys. Chem. Chem. Phys., 2015, 17, 32528
DOI: 10.1039/C5CP06364G

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