Effects of long-chain alcohols on the micellar properties of anionic surfactants in non-aqueous solutions by titration microcalorimetry

The power–time curves of micellar formation of two anionic surfactants, sodium laurate (SLA) and sodium dodecyl sulfate (SDS), in N,N-dimethyl acetamide (DMA) in the presence of various long-chain alcohols (1-heptanol, 1-octanol, 1-nonanol and 1-decanol) were measured by titration microcalorimetry at 298 K. The critical micelle concentrations (CMCs) of SLA and SDS under various conditions at 298 K were obtained based on the power–time curves. Thermodynamic parameters (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Updelta H^\circ_{\text{mic}} $$\end{document}, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Updelta S^\circ_{\text{mic}} $$\end{document} and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Updelta G^\circ_{\text{mic}} $$\end{document}) for micellar systems at 298 K were evaluated according to the power–time curves and the mass action model. The influences of the number of carbon-atom and the concentration of alcohol were investigated. Moreover, combined the thermodynamic parameters at 303, 308 and 313 K in our previous work and those of 298 K in the present work for SLA and SDS in DMA in the presence of long-chain alcohols, an enthalpy–entropy compensation effect was observed. The values of the enthalpy of micellization calculated by direct and indirect methods were made a comparison.