title: Swelling and Surface Interactions of End-Grafted Poly(2-vinylpyridine) Layers in Acidic Solution: Influence of Grafting Density and Salt Concentration.
abstract: In previous studies, the authors found that end-grafted layers of the weak polybase poly(2-vinylpyridine) (P2VP) in aqueous solutions do not only swell and collapse if the pH value and salt concentration are varied but also exhibit a pH- and salinity-dependent adhesion to microsized silica spheres. For a better understanding of these effects, in situ force measurements using the AFM colloidal probe technique were applied to end-grafted P2VP layers of different grafting densities in NaCl solutions at pH 2.5. Although a mushroom-to-brush transition could be seen in the dry state, the layers were in the brush regime in aqueous solutions at all NaCl concentrations and grafting densities. We observed an increase of the brush height with increasing grafting density and a salinity-dependent collapse and reswelling of the brushes. The adhesion between the P2VP layer and a silica sphere depended on both grafting density and salinity. At low salt concentrations, the adhesion reached its highest value at the intermediate grafting density and disappeared with denser brushes. Maximum adhesion was obtained for high NaCl concentrations and the lowest grafting density. From a detailed analysis of the experiments, we gained insight into chain stretching and density profiles under complex ionic conditions and into the mechanism of adhesion of polyelectrolytes to solid surfaces.
authors.affiliation: Leibniz Institute of Polymer Research Dresden , Hohe Str. 6, 01069 Dresden, Germany.|Department of Physics, Mansoura University , Mansoura 35516, Egypt.
authors.forename: Mahdy M
authors.initials: MM
authors.lastname: Elmahdy
authors.affiliation: Leibniz Institute of Polymer Research Dresden , Hohe Str. 6, 01069 Dresden, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Drechsler
authors.affiliation: Leibniz Institute of Polymer Research Dresden , Hohe Str. 6, 01069 Dresden, Germany.|Department of Chemistry, Hamilton Hall, University of Nebraska-Lincoln , 639 North 12th Street, Lincoln, Nebraska 68588, United States.
authors.forename: Petra
authors.initials: P
authors.lastname: Uhlmann
authors.affiliation: Leibniz Institute of Polymer Research Dresden , Hohe Str. 6, 01069 Dresden, Germany.|Physical Chemistry of Polymer Materials, Technische Universität Dresden , 01062 Dresden, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Stamm