Characterization and stability of catanionic vesicles formed by pseudo-tetraalkyl surfactant mixtures

Pucci, Carlotta
Pérez, Lourdes
La Mesa, Camillo
Pons Pons, Ramon

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Publication date

December 2014

DOI

10.1039/c4sm01575d

Publisher

Royal Society of Chemistry (RSC)

ISSN

1744-683X

Abstract

The phase behavior of an ad hoc synthesized surfactant, sodium 8-hexadecylsulfate (8-SHS), and its mixtures with didecyldimethylammonium bromide (DiDAB) in water is reported. We dealt with dilute concentration regimes, at a total surfactant content of <30 mmol kg-1 where vesicular aggregates may be formed. The high synergistic behavior of such catanionic mixtures is concomitant with strongly negative interaction parameters, β (≈-18 kBT), significant gain in the free energy of association, ΔGagg, and much lower association concentration compared to the pure surfactants. Vesicle size and ζ-potential depend on the mixture composition. Hydrodynamic diameters increase by progressive addition of oppositely charged surfactants to the one in excess...