Diffusion behavior of polyelectrolytes in dilute solution: coupling effects of hydrodynamic and Coulomb interactions

Abstract

The diffusion behavior of polyelectrolytes in dilute salt-free solution is studied through a hybrid mesoscale simulation technique that combines the molecular dynamics method and the multiparticle collision dynamics approach. To elucidate the effects of hydrodynamic interactions (HI), we compare results for hydrodynamic and random solvents. When HI are taken into account, we find that the chain diffusivity decreases initially and then increases gradually with the increasing strength of the Coulomb interaction. By contrast, when HI are switched off, the electrostatic-dependent diffusivity shows three distinct regions, and a plateau of approximately constant diffusivity manifests between two decreasing regions. The findings reveal that the dynamics of polyelectrolytes in dilute solution depend on the coupling effects of hydrodynamic and Coulomb interactions, and that these dynamics can be understood by considering the conformational changes of chains, the counterion condensation, and the dynamics of counterions