title: Collapse of spherical polyelectrolyte brushes in the presence of multivalent counterions.
abstract: We consider the interaction of multivalent counterions with spherical polyelectrolyte brushes (SPB). The SPB result if linear polyelectrolyte (PE) chains (contour length: 60 nm) are densely grafted to colloidal spheres of 116 nm in diameter. Dispersed in water, the surface layer consisting of chains of the strong PE poly(styrene sulfonic acid) (PSS) will swell. We demonstrate that successive addition of trivalent ions (La3+) leads to a collapse in which the surface layer is shrinking drastically. All findings are discussed on the base of a theoretical mean-field approach using the Donnan equilibrium. The ion exchange and a strong binding of trivalent ions by PE chains is followed up by a drop in the osmotic pressure inside the brush. This reduction is the driving force for the collapse. The strong ion-chain correlation is discussed with results obtained from molecular dynamics simulations.
authors.affiliation: Physikalische Chemie I, University of Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Yu
authors.initials: Y
authors.lastname: Mei
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Lauterbach
authors.forename: Martin
authors.initials: M
authors.lastname: Hoffmann
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Borisov
authors.forename: Matthias
authors.initials: M
authors.lastname: Ballauff
authors.forename: Arben
authors.initials: A
authors.lastname: Jusufi
mesh_terms: D002412:Cations; D004573:Electrolytes / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D008956:Models, Chemical; D011137:Polystyrenes / Q000737:chemistry*
chemical_list: D002412:Cations; D004573:Electrolytes; D011137:Polystyrenes; D007811:Lanthanum; C003321:polystyrene sulfonic acid