Dynamics of dense Polyelectrolyte Solutions

TL;DR

This paper models the complex dynamics of dense polyelectrolyte solutions, revealing how interactions and multiple length scales influence diffusion, viscosity, and screening effects within the system.

Contribution

It introduces a dynamical RPA framework for analyzing dense polyelectrolyte solutions, incorporating hydrodynamics and collective coordinates to understand their complex behavior.

Findings

Debye-Hückel-like screening depends on frequency

Nontrivial diffusive behavior due to component coupling

Relationships among static, hydrodynamic, and Debye lengths

Abstract

We investigate a system of dense polyelectrolytes in solution. The Langevin dynamics of the system with linearized hydrodynamics is formulated in the functional integral formalism and a transformation made to collective coordinates. Within a dynamical Random Phase Approximation (RPA) integration over the counter- and salt ions produces the Debye-H\"uckel-like screening of the Coulomb interactions with dependence on the frequency only as part of a more complicated coupling structure. We investigate the dynamics of the structure factor as well as the collective diffusion coefficient and comment upon the viscosity of the whole system of polymers with counterions and fluid in the simplest approximation. The coupling of the various components of the system produces nontrivial diffusive behavior. We draw conclusions about the relationship of the three length scales in the present system, i.e. the static screening length, the hydrodynamic screening length and the Debye length.