Correlation and prediction of critical micelle concentration using polar surface area and LFER methods

Models of critical micelle concentration (CMC) using two separate methods, the linear free energy relationship of Abraham and a modified polar surface area approach, are reported. Individual models are developed for anionic, non-ionic and structurally diverse molecules, the last including many commercially important drugs such as analgesics, anaesthetics and antibiotics. Statistical analysis demonstrates the predictive accuracy of both methods, with R-2 values around 0.90 throughout. A further model for the simultaneous calculation of CMC for anionic and nonionic surfactants was developed, giving reasonable correlations of observed vs calculated CMC. Both methods show similar patterns in regression coefficients; the most significant factor affecting a molecule's CMC is its size, with larger surfactants giving lower CMC. Strong H-bond acidic surfactants form micelles at lower concentrations, and increasing the H-bond basicity of a surfactant acts to raise the CMC. Copyright (C) 2004 John Wiley Sons, Ltd.