Polyelectrolyte adsorption on heterogeneously charged surfaces

The adsorption transition of a uniformly charged polyelectrolyte onto heterogeneously charged surfaces has been investigated using off-lattice Monte Carlo simulations. Each of these surfaces contains both positive and negative charges. In addition to the usual case of adsorption of a polyelectrolyte to a surface with net charge opposite to that of the polymer, we show that a polyelectrolyte can adsorb onto a surface with net surface charge density similar to that of the polyelectrolyte. This adsorption is caused by the spatial inhomogeneity of the surface charges, which creates attractive regions with charge density different from the overall charge density of the surface. The spatial inhomogeneity of the surface charges also leads to differences in the conformation of the adsorbed polyelectrolyte. The critical conditions of strength and range of electrostatic interactions and chain length necessary for adsorption of a polyelectrolyte to a heterogeneously charged surface are demonstrated.