Interfacial composition and solubilization of microemulsion systems containing mixed surfactants C12mimBr and Brij35: effects of surfactant composition, temperature, and salinity

The composition of the interfacial layer and solubilization of the microemulsions containing mixed cationic and nonionic surfactants (C12mimBr-Brij35) were studied and compared based on the mass and the number of moles of the surfactants, respectively. As XC12mimBr\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {X}_{C_{12}\mathrm{mimBr}} $$\end{document} (mole fractions of C12mimBr in C12mimBr-Brij35 mixture) increases, the total masses of the surfactants (mSs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {m}_S^s $$\end{document}) decrease, whereas the total number of moles of surfactants (nSS\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {n}_S^S $$\end{document}) increases in the interfacial layer. This opposite pattern of change between mSs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {m}_S^s $$\end{document} and nSS\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {n}_S^S $$\end{document} against XC12mimBr\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {X}_{C_{12}\mathrm{mimBr}} $$\end{document} is due to the significant difference in the molecular mass between the two surfactants. The mass solubilization parameter of the microemulsions, SPm∗\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\mathrm{SP}}_m^{\ast } $$\end{document}, increases and follows a curve that concaves downward as XC12mimBr\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {X}_{C_{12}\mathrm{mimBr}} $$\end{document} values increase. However, the molar solubilization parameter, SPn∗\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\mathrm{SP}}_n^{\ast } $$\end{document}, would decrease as XC12mimBr\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {X}_{C_{12}\mathrm{mimBr}} $$\end{document} increases. The physicochemical properties of the microemulsions are less sensitive to both temperature and salinity.