Structure of Surfaces and Interfaces of Poly( N,N -dimethylacrylamide) Hydrogels

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 s...

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Bibliographic Details
Published inarXiv.org
Main Authors Sudre, Guillaume, Hourdet, Dominique, Cousin, Fabrice, Creton, Costantino, Tran, Yvette
Format Paper Journal Article
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 23.01.2017
Subjects
Chemical synthesis
Crosslinking
Free radical polymerization
Free radicals
Hydrogels
Hydrophobicity
Physics - Soft Condensed Matter
Reflectance
Rheological properties
Rheology
Surface properties
Surface structure
Surface treatment
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Summary: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.
ISSN:2331-8422
DOI:10.48550/arxiv.1701.06389