SURFACE-DIFFUSION IN SODIUM DODECYL SULFATE-STABILIZED THIN LIQUID-FILMS

The surface dynamics of the fluorescent anionic surfactant 5-N-(octadecanoyl) aminofluorescein in microscopic, suspended thin films stabilized by sodium dodecyl sulfate (SDS) have been investigated by fluorescence recovery after photobleaching. The data revealed that the surface of common black films is in a highly dynamic state and that fluorophore mobility is due to diffusion rather than to flow. The influence of viscosity on film drainage, thickness, and dynamics was investigated with solutions containing glycerol. The rate of film drainage was reduced under these conditions and the limiting thickness of the drained film was significantly increased. The diffusion coefficient of surface-adsorbed fluorophore decreased with increasing viscosity, confirming the presence of an interaction between the surface film and the interlamellar liquid. However, the dependence of lateral diffusion on the reciprocal of bulk viscosity was nonlinear. © 1990.