P.D.T. Huibers(1), V.S. Lobanov(2), A.R. Katritzky(2), D.O. Shah(1), M. Karelson(3)
(1) Dept. of Chemical Engineering, Center for Surface Science and Engineering, U. of
Florida, Gainesville, FL 32611-6005
(2) Dept. of Chemistry, Center for Heterocyclic Chemistry, U. of Florida, Gainesville,
FL 32611-7200
(3) Dept. of Chemistry, U. of Tartu, 2 Jakobi Str., Tartu EE 2400, Estonia
Relationships between the molecular structure and the critical micelle concentration (cmc) of anionic surfactants were investigated using a quantitative structure- property relationship (QSPR) approach. Measured cmc values for 119 anionic structures were considered, representing sodium alkyl sulfates and sodium sulfonates with a wide variety of hydrophobic and hydrophilic structures. The best multiple linear regression model involved three terms (descriptors) and had a correlation coefficient of R2 = 0.940. Very good correlations (R2 = 0.988) were obtained using three descriptors for a subset of 68 structures, with structural variation only in the hydrophobic domain. From the descriptors used in these regressions, one can conclude that the cmc is primarily dependent on the size (volume or surface area) of the hydrophobic domain, and to a lesser extent on the structural complexity of the surfactant molecule.
Key Words: critical micelle concentration; cmc; anionic surfactants; quantitative structure-property relationships; QSPR; molecular connectivity; dipole moment; topology; property prediction; CODESSA; MOPAC.