Effect of surfactant on the drainage of an aqueous film between an oil droplet approaching a hydrophobic solid surface

Abstract

The effect of cetyltrimethylammonium bromide concentration above the critical micelle concentration on the profile of aqueous films between an approaching squalene droplet and a hydrophobic silica surface is investigated using the technique of imaging reflectometry. Drainage through the film periphery was observed to display viscous fingering effects and occurred via dendritic channels. This is explained to result from a combination of viscosity and interfacial tension effects. To our knowledge, this is the first time behavior such as this has been observed in a system involving the approach of a droplet to a solid surface.