Thermodynamics of Solubilization of Pentanol in Sodium Dodecyl Sulfate-Dodecyldimethylamine Oxide Mixed Micelles

✍ Scribed by S. Milioto; R. Crisantino; R. De Lisi

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 341 KB
• Volume: 166
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1994.1306

✦ Synopsis

Heat capacity and density measurements of pentanol ((\mathrm{PeOH})-) sodium dodecyl sulfate ( (\mathrm{NaDS}) )-dodecyldimethylamine oxidewatler mixtures were carricd out at (0.03 \mathrm{~m}) PeOH as a function of the total surfactants concentration (\left(m_{1}\right)) at different ratios ( (X_{\text {Nals }}) ). From experimental data, the apparent molar volumes ( (V_{\varangle, \mathrm{R}}) ) and heat capacities (\left(C_{\varangle, R}\right)) of (\mathrm{PeOH}) in the surfactants mixture solutions were calculated. As a general feature, at a given mixture composition, (V_{\phi, \mathrm{R}}) increases monotonically with (m_{\mathrm{t}}) as observed in pure surfactants. In the cases of (X_{\mathrm{NaDS}}=0.1) and (0.3, V_{\phi, R}) drops at about 0.1 and (0.15 \mathrm{~m}), respectively. The decreasing (C_{\phi, R}) vs (m_{1}) curve shows peculiarities which were ascribed to the presence of a liquid crystalline phase for (X_{\mathrm{NaDS}}=) 0.1 and 0.3 and of a structural micellar transition for (X_{\mathrm{NaDS}}=) 0.6 and 0.9 . At a given (X_{\mathrm{NaDS}}), the dependence of the apparent molar property of (\mathrm{PeOH}) on (\boldsymbol{m}{1}) was rationalized in terms of the distribution constant of alcohol between the aqueous and the micellar phases ( (K) ) and its partial molar property in the aqueous and the micellar phases. The standard free energy, calculated from the (K) values, and the partial molar properties of (\mathrm{PeOH}) in the surfactant-surfactant micelles change linearly with (X{\mathrm{NaDS}}) according to the ideal behavior. (1994 Academic Press. Inc.