Particle Charging and Stabilization in Non-Polar Liquids by Reversed Surfactant Micelles

It is well known that ionic surfactants such as AOT are able to induce strong charging effects in nonpolar liquids. They avoid the large energetic barrier associated with the introduction of small ions in low dielectric media by forming charged micellar aggregates. Here we report evidence that nonionic surfactants have a very similar effect on nonpolar oils. The content of water solubilized in the micelle core, the overall micelle size and the fraction of charged micelles are extracted from Karl Fischer titration, dynamic light scattering, and precision conductometry data. Electrokinetic studies of added colloidal particles further reveal the micelles' ability to create and screen electric charges on surface of suspended solid particles. We interpret the observed behavior using a statistical mechanics approach originally proposed for ionic surfactant based microemulsions. Our findings suggest that nonionic surfactants can play a key role in the industrially important task of controlling charges in nonpolar solvents.