On the Spreading of an Insoluble Surfactant over a Thin Viscous Liquid Layer

Reported here are results of a theoretical and experimental study of the spreading of an insoluble surfactant over a thin liquid layer. Initial concentrations of surfactant above and below CMC have been considered. If the concentration is above CMC two distinct stages of spreading are found. (i) The first stage is the faster, and it is connected with micelle dissolution; (ii) the second stage is the slower, when the surfactant concentration falls below CMC. In the second stage, the formation of a dry spot in the center of the film is observed. A similarity solution of the corresponding equations for spreading gives good agreement with experimental observations.