Length Dependent Electrophoretic Mobility of Polyelectrolytes in Uniform Shear Flow

Recent work suggests that hydrodynamic interactions generated by an electric field acting on a polyelectrolyte are not fully screened. As a result the electrophorectic mobility of an elongated polyelectrolyte may contain additional contributions from interactions between distant parts of the chain. We have developed a Brownian-dynamics simulation that includes electrically driven hydrodynamic interactions, which are dipolar in nature in low-salt conditions. In the absence of flow, the electrophoretic mobility is independent of the chain length as the polymer retains a spherical shape. However, in a uniform shear flow we find that the electrophoretic mobility increases with shear rate, initially linearly but later saturating at a value approximately 10% higher than the mobility of the undeformed chain. At the same flow rate, the electrophoretic mobility of a sheared polyelectrolyte varies with the contour length.