Sven H. Behrens, Qiong Guo, and Virendra Singh. School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332
According to conventional wisdom, ionization processes do not occur in media of low electric permittivity, where they require a higher energy input than thermal motion can provide (equivalently, the Bjerrum length is much larger than a typical ion size), and thus electric charge is not commonly considered relevant for particle interaction in nonpolar liquids. Notable exceptions occur in systems with inverse micelles that can take the role of large mobile ions and promote both the fomation and the screening of surface charge on dispersed colloidal particles. We report experiments correlating the size and charging effects of different types of micelles and point out striking similarities as well as marked differences between these micellar charge carriers in oily media and salt ions in aqueous solutions.