Effect of cations on the structure of sodium bis(2-ethylhexyl)sulfosuccinate water-in-oil microemulsion

• Published in: Journal of applied crystallography Vol. 40; no. s1; pp. s274 - s278
• Main Authors: Kawai-Hirai, Rika, Hirai, Mitsuhiro
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England Blackwell Publishing Ltd 01.04.2007
• Subjects: AOT; cations; Crystal structure; Crystallography; Microemulsions; Salt; salts; sodium bis(2-ethylhexyl)sulfosuccinate
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S0021889807008151

We have characterized the structure of water/sodium bis(2‐ethylhexyl)sulfosuccinate (AOT)/isooctane water‐in‐oil microemulsion depending on the concentrations of monovalent and divalent cations (Na+, K+, Ca2+) in the water pool. We have found that the presence of salts affects the microemulsion structures differently at low and high water contents. Increasing the salt concentration suppresses the oligomerization of the microemulsions at low water content, whereas it reduces the microemulsion radius at high water content. The present results clearly indicate that not only electrostatic repulsion between AOT headgroups but also negative or positive hydration effects by salts dominate the structure and dynamics of AOT microemulsions, as suggested by a recent molecular dynamics simulation.