Probing pH-Responsive Interactions between Polymer Brushes and Hydrogels by Neutron Reflectivity

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• 作者：Guillaume Sudre ; Dominique Hourdet ; Costantino Creton ; Fabrice Cousin ; Yvette Tran
• 刊名：Langmuir
• 出版年：2014
• 出版时间：August 19, 2014
• 年：2014
• 卷：30
• 期：32
• 页码：9700-9706
• 全文大小：316K
• ISSN：1520-5827

文摘

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.