WETTING OF EMULSIONS DROPLETS - FROM MACROSCOPIC TO COLLOIDAL SCALE

By using large oil-in-water droplets covered with ionic surfactant we measure contact angles to deduce the adhesive energy between macroscop ic interfaces as a function of the temperature T and the salt concentr ation C. A wetting transition takes place at a well defined temperatur e T(C). At the colloidal scale, we have observed that submicron dropl ets covered by the same monolayers undergo a phases separation. We sho w that the phases diagram can be quantitatively predicted from the mac roscopic contact angles. However, to describe the colloidal phase sepa ration we have to account for both the entropy and the deformation ind uced by the wetting of the droplets. Finally, our results show how mac roscopic wetting transition can be shifted at the colloidal scale wher e droplets entropy plays an important role.