title: Probing pH-responsive interactions between polymer brushes and hydrogels by neutron reflectivity.
abstract: We investigated the effect of specific interactions on the structure of interfaces between a brush and a hydrogel on the polymer chain length scale. We used a model system for which the interactions between the brush and the gel are switchable. We synthesized weak polyelectrolyte brushes of poly(acrylic acid) and hydrogels of polyacrylamide and poly(N,N-dimethylacrylamide) which interact solely when the poly(acrylic acid) is mainly in its acidic form. The monomer density profiles of the poly(acrylic acid) brush immersed in pure deuterium oxide (D2O) or in contact with a D2O-swollen gel were determined by neutron reflectivity. At pH 2 when the brush is in its neutral form, it interacts with the gel by hydrogen bonds while at pH 9 when the brush is a polyelectrolyte it is not interacting with the gel. Our results show that the presence of interactions with the gel at pH 2 increases the swelling ratio of the brush relative to that in pure D2O, meaning that the brushes exhibit conformations which are more extended from the surface than in the absence of interactions.
authors.affiliation: Laboratoire de Science et Ingénierie de la Matière Molle, UMR 7615 CNRS/UPMC/ESPCI ParisTech, 10 rue Vauquelin, F-75231 Paris Cedex 5, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Sudre
authors.forename: Dominique
authors.initials: D
authors.lastname: Hourdet
authors.forename: Costantino
authors.initials: C
authors.lastname: Creton
authors.forename: Fabrice
authors.initials: F
authors.lastname: Cousin
authors.forename: Yvette
authors.initials: Y
authors.lastname: Tran
mesh_terms: D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009502:Neutrons; D011108:Polymers / Q000737:chemistry*
chemical_list: D020100:Hydrogels; D011108:Polymers