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.

GCMe: Efficient Implementation of the Gaussian Core Model with Smeared Electrostatic Interactions for Molecular Dynamics Simulations of Soft Matter Systems

“…Existing studies have largely focused on how repulsive image charges and finite potential differences influence polyelectrolyte adsorption behavior and energy storage. For example, Monte Carlo simulations by Wang et al 67 have elucidated how repulsive image charges can either enhance or penalize polyelectrolyte adsorption depending on the polyelectrolyte charge fraction and surface charge distribution. MD efforts by Bagchi et al 68 have revealed that repulsive image charges give rise to enhanced energy storage in polyelectrolyte EDLCs at low surface charge densities due to charge amplification.…”