It is generally assumed that adsorption of surface active agents at liquid interfaces is diffusion-controlled (when the liquids are at rest). Evidence is growing that most frequently, adsorption is slowed down by energetic barriers, electrostatic in the case of charged surface active agents. We will show examples of this situation with ionic surfactants and colloidal nanoparticles. In the case of electrostatic barriers, the classical diffusion model of Ward and Tordai can be implemented, leading to a good agreement with the experiments. One missing feature is the determination of the time after which the barrier is overcome, which theory is not yet able to predict. We will show that this time is drastically affected by the presence of convection. We will also show important consequences of the presence of these barriers in various phenomena : withdrawal of thin films on plates (Landau-Levich problem), foaming and emulsification, and foam and emulsion coarsening.ReferencesH. Ritacco, D.Langevin, H.Diamant, D.Andelman, �Dynamic surface tension of aqueous solutions of ionic surfactants: role of electrostatics�, Langmuir 2011, 27, 1009D.Georgieva, V.Schmitt, F.Leal-Calderon, D.Langevin �On the possible role of the surface elasticity in emulsion stability� Langmuir, 25, 2009, 5565A.Stocco, E.Rio, B.P.Binks, D.Langevin �Aqueous foams stabilized solely by particles� Soft Matter 2011, 7, 1260J.Delacotte, L.Montel, F.Restagno, B.Scheid, B.Dollet, H.A.Stone, D.Langevin, E.Rio 'Surfactant-induced thickening in liquid film coating� Phys.Fluids, submitted

On adsorption barriers at liquid interfaces

242nd National Meeting (2011)

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