Space‐charge‐perturbed electrophoresis in nonpolar colloidal dispersions

This paper reports the observation of bipolar, space‐charge‐perturbed transport in colloidal dispersions using an experimental technique that time‐resolves electrophoresis in nonpolar colloidal systems. Unlike existing methods for studying electrophoresis, this technique can be applied to dispersions of diverse types and concentrations over a wide range of electric fields, including the space‐charge‐perturbed conditions often encountered in practical applications. The phenomenon is investigated as a special case of dielectric relaxation in a leaky capacitor connected in series to a perfect one. Using the first principle charge transport theory, such dielectric relaxation, occurring under the non‐Ohmic supply and space‐charge‐perturbed transport conditions, is shown to differ from that expected by the conventional equivalent‐circuit treatment. The combined theoretical analysis and the experimental technique provides a means for independently determining the densities and mobilities of charged species in su...