Separating diffusion from dilation in the adsorption of surfactants.

Surfactants are often employed in highly dynamic environments, such as in the oil and gas industry, where large variations in both surfactant concentrations as well as distortions of bubble and foam geometries can exist. In such scenarios, the surface tension changes are a result of surfactants diffusing to the interface and/or being spread apart due to interfacial dilation. While previous studies have mainly focused on diffusion-driven adsorption, we use surface-area-controlled bubble tensiometry to characterize dynamic surface tension in terms of separate diffusion and dilation effects during surfactant adsorption to the liquid-vapor interface. Distinguishing these behaviors provides a more specific characterization of dynamic surfactant behaviors that can ultimately provide a better insight into how to better select and utilize surfactants for a variety of applications.