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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 R2 values around 0.90 throughout. A further model for the simultaneous calculation of CMC for anionic and non‐ionic 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 © 2004 John Wiley & Sons, Ltd.

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Linear free energy relationship (LFER) methods were used to construct a model for the solubility of a species in supercritical CO2. The final model was based on 64 molecules and 782 data points, employing a modified version of the Abraham LFER equation incorporating π1, the dipolarity/polarizability of the CO2 at a given density. This allowed us to model data ranging from 308 to 435 K and 74.3 to 410 bar, with an accuracy of ±0.65 log mole fraction units. The model shows that solubility in supercritical CO2 is favoured by the presence of π and n electron pairs and hydrogen‐bond basicity. Solute size and hydrogen‐bond acidity are less important, whereas polarity/polarizability is statistically insignificant. Copyright © 2001 John Wiley & Sons, Ltd.