Spreading of surfactant solutions over thin aqueous layers at low concentrations: Influence of solubility

A small droplet of aqueous surfactant solution at concentration below CMC was deposited on a thin water layer. A moving circular wave in the centre was formed. The time evolution of the radius of the wave was monitored. Two surfactants of different solubility were used. It was shown that the time evolution of the moving front (i) proceeds in two stages: a fast first stage and slower second stage; (ii) the time evolution of the front motion substantially depends on the surfactant solubility. We suggest a qualitative explanation of the phenomenon, which reasonably agrees with our experimental observations.

A circular moving front of radius R(t)R(t) on a top of thin aqueous layer of thickness h0h0 after a deposition of a small droplet of aqueous surfactant solution.Figure optionsDownload as PowerPoint slide