Abstract
The micropolarity of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles prepared in supercritical ethane and near-critical propane has been determined in terms of a solvent polarity parameter, E T(30) values, by using absorption probes, 1-ethyl-4-methoxycarbonyl pyridinium iodide and 2,6-diphenyl-4-(2,4,6-triphenylpyridinio)-phenolate as a functions of pressure and the molar ratio of water to AOT, W 0, at a constant temperature of 310 K. The micropolarity comparable to that of ethanol was observed for reverse micelles containing water of W 0 = 2. The micropolarity increased with the water content and became independent of pressure after the system changed to a one-phase reverse micelle solution. For a given W 0 value, no difference in the micropolarity was noticed in the micelles prepared in ethane and propane. Phase behaviour investigations have revealed that complete dissolution of 50 mM AOT occurred at 20 MPa in supercritical ethane, while a much lower pressure of 1 MPa was required in near-critical propane. The amount of water solubilized in reverse micelles formed in supercritical ethane was relatively low, reaching a W 0 value of 7 at 36 MPa. In contrast, the amount of water solubilized in near-critical propane reverse micelles was W 0 = 11 at a much lower pressure of 6 MPa. A higher pressure was required to solubilize larger amount of water in reverse micelles prepared in both ethane and propane.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Received: 9 October 1998 Accepted in revised form: 12 February 1999
Rights and permissions
About this article
Cite this article
Shervani, Z., Ikushima, Y. Micropolarity of sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles prepared in supercritical ethane and near-critical propane. Colloid Polym Sci 277, 595–600 (1999). https://doi.org/10.1007/s003960050431
Issue Date:
DOI: https://doi.org/10.1007/s003960050431