The Effect of Salt and Monomer Distribution on the Electroresponse of Partially Charged Polyelectrolyte Brushes

ABSTRACT Polyelectrolyte brushes reorganize when they are placed in electric fields, which allows for a field‐induced collapse or swelling. While these systems have been studied theoretically in detail under salt‐free conditions, the effect of salt on the electroresponse has been less systematically explored. Yet, in potential applications, for example, for anti‐fouling, in biomedical systems or in the food industry, polyelectrolyte brushes are almost always in contact with solutions that contain salt. We use coarse‐grained molecular dynamic simulations and Scheutjens‐Fleer self‐consistent field theory to study the effect of salt on the electroresponse of two different polyelectrolyte brushes: a random copolymer of neutral and charged monomers and a gradient copolymer where the composition gradually changes from neutral at the grafting plane to charged at the free end. We find that salt only has a limited effect of the electroresponse when the brush is in the osmotic regime at low salt concentrations, while it stifles the response in the salted regime at high salt concentrations. Additionally, we find that the electroresponse in the transition between these regimes is significantly affected by chain architecture. Our results show that the electroresponse of polyelectrolyte brushes can still be used at salt concentrations as they occur in practical applications.