Effective Interactions Between Rigid Polyelectrolytes and Like-charged Planar Surfaces

We study the effective interaction between a planar array of uniformly negatively charged, stiff rods parallel to a negatively charged planar substrate in the absence of salt in a continuous, isotropic dielectric medium. Using Brownian dynamics simulations, we examine the general effects of counterion valence, rod spacing, macroion charge densities, and the rod size on the attractive rod-surface interaction force. At room temperature divalent as well as monovalent counterions mediate an interaction that can be repulsive or attractive upon adjusting either the macroion charge densities or the rod radius. Finally, we examine the effects of discretizing the surface charge as laterally mobile monovalent anions and of electrostatic images in the substrate. Present address: NCSA, University of Illinois, 405 N. Mathews, Urbana, IL 61801;