title: Polyelectrolyte brushes in external fields: molecular dynamics simulations and mean-field theory.
abstract: A mean-field model is developed to predict the layer-thickness of sparse and salt-free polyelectrolyte brushes, exposed to an external electric field, which attracts the polyelectrolytes to the substrate. In molecular dynamics simulations, it is shown that a fraction of polymers collapses entirely to screen the charge of the substrate. The remaining brushes are then treated as field-free brushes at reduced grafting density. The mean-field model may thus be applied to field-free brushes, both in their osmotic and their weak charge regimes. It yields simple, closed equations for the brush height and for the partition of counterions in- and outside the brushes, and accurately reproduces simulation data of the collapse of the brushes during the crossover between both charge regimes.
authors.affiliation: Department of Physics and ITPA, Xiamen University, Xiamen 361005, P. R. China. merlitz@posteo.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Merlitz
authors.forename: Chengwu
authors.initials: C
authors.lastname: Li
authors.forename: Chenxu
authors.initials: C
authors.lastname: Wu
authors.forename: Jens-Uwe
authors.initials: JU
authors.lastname: Sommer
mesh_terms: D004573:Electrolytes / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D009995:Osmosis; D011108:Polymers / Q000737:chemistry*
chemical_list: D004573:Electrolytes; D011108:Polymers