Kinetics of Surfactant Adsorption: The Free Energy Approach

We review the free energy approach to the kinetics of surfactant adsorption at fluid/fluid interfaces. The formalism is applied to several systems. For non-ionic surfactant solutions the results coincide with previous models while indicating their limits of validity. We study the case of surfactant mixtures, focusing on the relation between the mixture kinetics and the properties of its individual constituents. Strong electrostatic interactions in salt-free ionic surfactant solutions drastically modify the adsorption kinetics. In this case the theory accounts for experimental results which could not be previously understood. The effect of screening by added salt is studied as well. Our theoretical predictions are compared with available experiments.