Mechanisms of Electric Charging By Surfactants in Nonpolar Dispersions

We present electric charging phenomena caused by surfactants in nonpolar media, and apply small variations in the surfactant composition to identify some of the physicochemical parameters crucial for the charging process. Although we observe striking differences to the more familiar charging in aqueous media, our experiments nonetheless support the notion that even in nonpolar systems water plays an important and multi-facetted role for charge formation. For the charging of polymer particles in nonpolar solutions of ‘humid’ surfactant micelles, we discuss a hypothetical two-step mechanism involving the formation and surface adsorption of micellar ions with substantial size asymmetry.