Energetics of sodium dodecylsulfate-dodecyldimethylamine oxide mixed micelle formation |
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Authors: | R Crisantino R De Lisi S Milioto |
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Institution: | (1) Dipartimento di Chimica fisica, Università di Palermo, via Archirafi 26, 90123 Palermo, Italy |
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Abstract: | Enthalpies of dilution and osmotic coefficients of the sodium dodecyl-sulfate (NaDS)-dodecyldimethylamine oxide (DDAO) mixtures in water have been measured at 25 and 37°C, respectively. From the enthalpies of dilution the apparent molar relative enthalpies L were calculated. The change of the L vs. total molality mt profiles with the mole fraction reflects the variation of the ionic character of the mixed micelles. From the osmotic coefficients the nonideal free energy G
2
ni
were calculated. By combining G
2
ni
with the partial molar relative enthalpies, the nonideal entropies TS
2
ni
were determined. At a given mole fraction, G
2
ni
and TS
2
ni
values are decreasing and increasing respectively, tending to become constant at high mt. The excess properties for the mixed micelle formation were evaluated as a function of the mixture composition at some mt. The profiles are compared with those obtained from thermodynamics of binary liquid mixtures and the regular solution theory. |
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Keywords: | Sodium dodecylsulfate dodecyldimethylamine oxide mixed micelles surfactant mixtures enthalpies of dilution osmotic coefficients partial molar relative enthalpies of mixed micelles nonideal free energies of mixed micelles nonideal entropies of mixed micelles |
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