An empirical model to represent the CMC behavior of aqueous solutions of homologous series of nonionic surfactants, related to its chemical constitution

Abstract

• The Critical Micelle Concentration (CMC) is a fundamental property of surfactants. • An empirical model is presented based on the thermodynamics of micellization of a given homologous series of surfactants. • The reason for the observed increase and decrease in CMC value is explained. • The proposed model is compared with other empirical models and its quality to estimate the CMC is superior. Critical Micelle Concentration (CMC) is a fundamental property of surfactants in (aqueous) solution. The importance of defining the CMC of an aqueous surfactant solution is related to the different behavior and performance of the given system below and above its CMC, which has impact on the usage of this type of systems for different industrial applications. In this work, an empirical model is presented, based on the fundamental equation for the thermodynamics of micellization of a given homologous series of surfactants with the same chemical nature, to estimate the corresponding CMC. This simple model contains three adjustable parameters and allows predicting the log[CMC] of the nonionic surfactants polyoxyethylene alkyl ethers (C n E m ) in aqueous solution. The analysis of the three parameters showed that the hydrophobic characteristics play the major role in micelle formation. The polarity of the molecules is also important, but its effect is less pronounced. The proposed model is compared with other empirical models and its quality to estimate the CMC is superior.