(214ak) Polyelectrolyte Interactions: Theory and Simulation

Polyelectrolyte interactions govern many natural and technological processes. Recent experiments and simulations suggest like charged polymers to attract one another under certain conditions, owing to preferential counter-ion positioning between the two chains. Such attraction may have significant implications to nucleic acid delivery and polyelectrolyte film formation. We address here the problem of like-charged polymer attraction using a coarse grained model, consisting of two similarly charged aligned cylinders, oppositely charged spherical counter-ions, and spherical salt species. Employing Monte Carlo simulation, we show polymer-polymer attraction to correlate strongly with a Coulomb coupling parameter, defined as the ratio of the electrostatic interaction energy of two counter-ions at the cylinder surface to the thermal energy. We also find a significant influence of ion diameter in the regime where crowding induces ion positioning away from the cylinder surface. Two simple statistical mechanical models are proposed: a purely mean field model for larger counter-ion diameter, and a hybrid model for smaller counter-ion diameter where ions “condensed” to the cylinder surface are treated as a highly correlated 2-D one-component plasma, and ions away from the surface are treated in a mean field description. We discuss these results in light of recent experimental findings of significantly enhanced polyelectrolyte adsorption to electrified interfaces.