title: Structure of surfaces and interfaces of poly(N,N-dimethylacrylamide) hydrogels.
abstract: We investigated the surface structure of hydrogels of poly(N,N-dimethylacrylamide) (PDMA) hydrogels synthesized and cross-linked simultaneously by redox free radical polymerization. We demonstrate the existence of a less cross-linked layer at the surface of the gel at least at two different length scales characterized by shear rheology and by neutron reflectivity, suggesting the existence of a gradient in cross-linking. The composition of the layer is shown to depend on the degree of hydrophobicity of the mold surface and is weaker for more hydrophobic molds. While the macroscopic tests proved the existence of a relatively thick under-cross-linked layer, we also demonstrated by neutron reflectivity that the gel surface at the submicrometric scale (500 nm) was also affected by the surface treatment of the mold. These results should have important implications for the measurement of macroscopic surface properties of these hydrogels such as friction or adhesion.
authors: Laboratoire de Sciences et Ingénierie de la Matière Molle, UMR 7615 CNRS/UPMC/ESPCI ParisTech, Paris, France.
authors: Guillaume
authors: G
authors: Sudre
authors: Dominique
authors: D
authors: Hourdet
authors: Fabrice
authors: F
authors: Cousin
authors: Costantino
authors: C
authors: Creton
authors: Yvette
authors: Y
authors: Tran
mesh_terms: D000178:Acrylamides / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D012212:Rheology; D013499:Surface Properties; D013696:Temperature
chemical_list: D000178:Acrylamides; D020100:Hydrogels; C429790:poly(N,N-dimethylacrylamide)