Spreading of Surfactant Solutions
Friday, January 12, 2001 - 2:45pm - 3:30pm
Anne-Marie Cazabat (Collège de France)
The spontaneous spreading of solutions of nonionic CnEm surfactants in ethylene and diethylene glycol on hydrophilic surfaces is controlled by the relative humidity RH of the gas phase, and the relative surfactant concentration c* = c / cmc. In the (c*,RH) plane, fast dendritic spreading is observed inside a well defined domain, while normal spreading is observed outside. Also the characteristics of the dendritic pattern depend on the position in the plane. The relative humidity controls the thickness of the preexisting water film on these hydrophilic substrates. It is also possible to spin coat an ethylene or diethylene glycol film on the substrate. Depending on the film thickness, the dendritic pattern may be strongly modified. The experimental data are analyzed in reference to the models by Troian et al.