(421k) Electrophoresis of a Deformable Polyelectrolyte: Effects of Double-Layer Polarization, Effective Charge, and Electroosmotic Flow

   The electrophoresis of a deformable polyelectrolyte (PE) is studied theoretically by considering a Poisson-Nernst-Planck model coupled with modified Navier-Stokes equations, taking account of the effects of double-layer polarization, counterion condensation, and electroosmotic flow. The influences of the local electric field and the effective PE charge on the PE mobility are discussed, thereby providing a complete picture for the phenomenon under consideration. Our model explains successfully the presence of a local minimum in the mobility of a highly charged PE as bulk salt concentration varies observed experimentally. Numerical simulation also reveals several interesting and important results. For example, the more a PE is stretched in the direction of electrophoresis the larger is its mobility. As the double layer gets thin, the local electric field becomes independent of the PE shape, and its behavior depends mainly on its effective charge. We show that the force which stretches a PE is maximal when it is spherical, and decreases with increasing aspect ratio, which has not been reported previously.