Dynamic surface tension in concentrated solutions of CnEm surfactants: A comparison between the theory and experiment

Dynamic surface tension (DST) measurements have been carried out with a ser ies of CnE6-type surfactants with varying alkyl chain length (n = 10-16). M ajor emphasis has been placed on the DST relaxation in complex solutions co ntaining both the micellar and monomer forms of surfactant. This paper also provides a step-by-step guidance to the theoretical interpretation of DST data for micellar solutions. Distributions of monomers and micelles in the vicinity of the gas/liquid interface, adsorption kinetics, and DST relaxati on curves have been simulated in the framework of the Fainerman theory (Fai nerman, V. B. Kolloid Z. 1981, 43, 94) explicitly allowing for monomer/mice lle interconversation. A thorough numerical analysis has shown that althoug h the Fainerman theory can follow the general experimental trends, it clear ly lacks the flexibility needed to provide a self-consistent and quantitati vely correct description of the process. Possible reasons for this disagree ment are discussed.