Volumes and heat capacities of anionic-nonionic surfactant mixtures |
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Authors: | S Milioto R Crisantino R De Lisi A Inglese |
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Institution: | (1) Dipartimento di Chimica Fisica, Università di Palermo, via Archirafi 26, 90123 Palermo, Italy;(2) Dipartimento di Chimica, Università di Bari, via Amendola 173, 70126 Bari, Italy |
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Abstract: | Density, heat capacity and surface tension measurements of sodium decylsulfate (NaDeS)-dodecyldimethylamine oxide (DDAO)-water mixtures were carried out as functions of the surfactants total molality mt at fixed stoichiometric mixture compositions XNaDeS. From the surface tension data, the critical micelle concentration of NaDeS-DDAO mixtures as a function of XNaDeS were obtained. From density and heat capacity data, the apparent molar volume V ,2 and heat capacity C ,2 of NaDeS-DDAO mixtures in water were calculated, respectively. At a given mole fraction, V ,2 and C ,2 monotonically increases and decreases, respectively, with increasing mt. However, anomalies were observed at XNaDeS=0.1 and 0.3 for both V ,2 and C ,2 vs. mt curves. The nonideal contributions to the thermodynamic properties for the formation of surfactant-surfactant mixed micelles in water by mixing aqueous solutions of pure NaDeS and DDAO micelles were calculated at 0.3 mol-kg–1 for the micellized surfactants mixture. The excess volume Vexc and heat capacity as functions of XNaDeS are concave and S-shaped curves, respectively. All the properties are compared to those for sodium dodecylsulfate-DDAO mixture. In addition, to clarify the effect of the change in the hydrophobicity of the surfactants mixtures Vexc for the dodecyltrimethylammonium bromide-decyltrimethylammonium bromide mixture were calculated from literature data. |
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Keywords: | Sodium decylsulfate dodecyldimethylamine oxide surfactants mixtures critical micelle concentrations surfactant-surfactant mixed micelles volume heat capacity excess volume of mixed micelles excess heat capacity of mixed micelles |
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