Electrophoresis of a Spherical Polyelectrolyte-Grafted Colloid in Monovalent Salt Solutions: Comparison of Molecular Dynamics Simulations with Theory and Numerical Calculations

Abstract

We study the electrophoresis of a polyelectrolyte-grafted colloid immersed in monovalent salt solution by means of explicit-ion molecular dynamics simulations including long-ranged hydrodynamic interactions via a lattice-Boltzmann fluid. We expand on our previous work on the subject by investigating the effect of charges and the salt concentration on both net-neutral and net-charged composites. We show that the dominant role of the polyelectrolytes at higher salt concentrations prevents a net-negative soft colloid to reverse mobility with respect to net charge except at extremely high net charges. We explain all our simulation results by examining in detail the ion and monomer density profiles around the colloid and the ratio of the Debye length to the brush height. Our simulation results show good agreement with both approximate analytic expressions and numerical solutions based on an extended standard electrokinetic model for polymer-grafted spherical colloids.