QSPR study of the first and second critical micelle concentrations of cationic surfactants

In colloidal and surface chemistry, the critical micelle concentration (CMC) is defined as the concentration of surfactants above which micelles form and almost all additional surfactants added to the system go to micelles. The CMC is an important characteristic of a surfactant. Before reaching the CMC, the surface tension changes strongly with the concentration of the surfactant. After reaching the CMC, the surface tension remains relatively constant or changes with a lower slope. Linear and nonlinear predictive models are derived for 50 ammonium and quaternary pyridinium cationic surfactants. Multilinear models were developed for both the first and second critical micelle concentrations (CMCs). Additionally, a general ANN model was deduced for the first CMC of all 50 cationic surfactants. Most of the descriptors in these models are related to the size and charge of the hydrophobic tail and to the size of the head. The multilinear model for the second CMC was more closely related to the hydrophobic domain of the surfactant than that of the first CMC. The QSPR models (linear and nonlinear) for the first CMC in this work could provide useful predictions of the CMC of structurally similar cationic surfactants.

Keywords:

surfactant , CMC , QSAR