Micropolarity of sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles prepared in supercritical ethane and near-critical propane |
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Authors: | Z Shervani Y Ikushima |
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Institution: | (1) Tohoku National Industrial Research Institute 4-2-1 Nigatake, Miyagino-ku 983 Sendai, Japan e-mail: zamir@tniri.go.jp Tel.: +81-22-237-5211 Fax: +81-22-237-5224, JP |
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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.
Received: 9 October 1998 Accepted in revised form: 12 February 1999 |
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Keywords: | Sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles Supercritical ethane Near-critical propane ET(30) values 2 6-diphenyl-4-(2 4 6-triphenylpyridinio)-phenolate |
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