Adsorption of Charge Sequence-Specific Polydisperse Polyelectrolytes

We use coarse-grained molecular dynamics to elucidate the influence of polydispersity on the adsorption of polydisperse bulk polyanionic chains onto a monodisperse polycationic brush. We consider primarily two different charge sequence scenarios, in which both polymer species are either block and alternating, for polyanions with a fixed dispersity D = 1.5. Polydispersity plays a negligible role when the brush cationic chains are in excess, since all polyanionic chains are adsorbed. In contrast, when the polyanions are in excess, polydispersity substantially decreases the fraction of chains adsorbed into the brush, irrespective of charge sequence, but increases the number of monomers adsorbed. These opposing trends are made possible by selective adsorption of long chains.