Effects of surface polarization and confinement on the structure and dynamics of polyelectrolytes

We investigate the effects of surface polarization on the structural and dynamical properties of confined polyelectrolyte solutions using molecular dynamics simulations. The system consists of unpolarizable polyions and counterions confined between two parallel surfaces. The surfaces are modeled as either non-polarizable or perfect metal. We analyze the accumulation of counterions and monomer units of polyions, the radial distribution function, and the ionic current as a function of the applied electric field. Our results reveal that metal surfaces induce the adsorption of counterions and polyions onto the surfaces. They are also responsible for reducing the attraction of counterions to polyion segments compared to non-polarizable surfaces. This redistribution leads to higher ionic mobility and an overall increase in ionic current for metal surfaces compared to that for non-polarizable ones, particularly at large separations. Confinement is more relevant for non-polarizable surfaces, where facilitated alignment of polyions with the electric field enhances the ionic current. These findings highlight the fundamental role of polarization and confinement effects in modifying the behavior of polyelectrolytes.