Use of Quantitative Structure Activity Relationships in Prediction of CMC of Nonionic Surfactants

The CMC of a set of 51 alkylpolyoxyethylene glycol ethers, R(EO)m, and alkylphenol (ethylene oxide) ethers, Rϕ(EO)m, was related to topological, electronic and molecular structure parameters using a stepwise regression method. In development of the models linear and quadratic terms were used without the use of cross terms. Different strategies including Akaike Information Criterion (AIC) were used for choosing the best model. Specification of the best model in agreement with the experiment indicates that volume of the hydrophobic group and surface area of the molecule play a major role in the mechanism of micellization of nonionic surfactants. It was demonstrated that the CMC of these compounds depend upon the orientation of carbon atoms at the interface of two phases. The predicted values of CMC using the best model for R(EO)m molecules containing even number of EO groups are better than that for the molecules with odd number of EOs.