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 (C 12 mimBr-Brij35) were studied and compared based on the mass and the number of moles of the surfactants, respectively. As X C 12 mimBr (mole fractions of C 12 mimBr in C 12 mimBr-Brij35 mixture) increases, the total masses of the surfactants ( m S s ) decrease, whereas the total number of moles of surfactants ( n S S ) increases in the interfacial layer. This opposite pattern of change between m S s and n S S against X C 12 mimBr is due to the significant difference in the molecular mass between the two surfactants. The mass solubilization parameter of the microemulsions, SP m ∗ , increases and follows a curve that concaves downward as X C 12 mimBr values increase. However, the molar solubilization parameter, SP n ∗ , would decrease as X C 12 mimBr increases. The physicochemical properties of the microemulsions are less sensitive to both temperature and salinity. Graphical abstract ᅟ