Why Are Hydrophobic/Water Interfaces Negatively Charged?


  • This work was supported by ANR 2010 BLAN 942 03 “LimOuzIne”. We thank F. Ganachaud, B. Jönsson, G. Karlström, and H. Wennerström for useful discussions and input and C. Labbez and D. Bouttes for their help on the pH-dependence calculation of the surface potential.


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Impure at heart: A pH-dependent negative charge of the interface between a hydrophobic phase and water results from the reaction of hydroxide ions with traces of fatty acids, contained in the hydrophobic phase (see scheme). This reaction explains the uptake of hydroxide ions by the interface with a large free energy change.