Adsorption of a Polyelectrolyte Chain at Dielectric Surfaces: Effects of Surface Charge Distribution and Relative Dielectric Permittivity

Abstract

The characteristics of a surface, such as surface charge distribution and permittivity, play significant roles in polyelectrolyte (PE) adsorption. However, systematic studies of these effects are rare in the literature. In this work, we employ a local lattice Monte Carlo algorithm to investigate the effects of dielectric contrast, charge fraction, and surface charge density on the adsorption behavior of a PE chain onto surfaces with different charge distributions. We consider three surface charge distributions: uniform (smeared), regular (periodic), and random. For the same total surface charge, the random charge distribution results in the strongest PE adsorption, while the uniform distribution shows the weakest. In the absence of dielectric contrast, the adsorption behaviors of a PE near the regularly charged surface are similar to those near the uniformly charged surface. In the presence of dielectric contrast, the image repulsion inhibits PE adsorption onto the uniformly charged surface. Surprisingly, surfaces with discrete charge distributions (regular and random) exhibit enhanced adsorption compared to that of the case with no image charge. In addition, the competition between image charge repulsion and electrostatic attraction from the surface results in nonmonotonic variation of the adsorbed amount with the PE charge fraction.