Surface tension relaxation in a surface containing surfactant particles

Abstract

At the surface of aqueous systems containing slightly soluble surfactants, slow relaxation processes occur that are accompanied by high values of the surface dilational modulus. A detailed investigation into these phenomena was carried out in systems containing dodecanol, tetradecanol and hexadecanol, using longitudinal surface waves and stress-relaxation experiments. The state of the surfaces involved resembles a monolayer after collapse: particles are present which do not consist of the thermodynamically stable bulk phase of the surfactant. A quantitative interpretation of the surface tension relaxation is given in terms of two processes: surfactant exchange in the surface between the monolayer and the particles, and diffusional exchange of surfactant between monolayer and bulk solution. The parameters characterizing these processes were measured; the values obtained are in satisfactory agreement with the results of other experiments.