Swelling of Polyelectrolyte and Polyzwitterion Brushes by Humid Vapors

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• 作者：Casey J. Galvin ; Michael D. Dimitriou ; Sushil K. Satija ; Jan Genzer
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：September 10, 2014
• 年：2014
• 卷：136
• 期：36
• 页码：12737-12745
• 全文大小：486K
• ISSN：1520-5126

文摘

Swelling behavior of polyelectrolyte and polyzwitterion brushes derived from poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) in water vapor is investigated using a combination of neutron and X-ray reflectivity and spectroscopic ellipsometry over a wide range of relative humidity (RH) levels. The extent of swelling depends strongly on the nature of the side-chain chemistry. For parent PDMAEMA, there is an apparent enrichment of water vapor at the polymer/air interface. Despite extensive swelling at high humidity level, no evidence of charge repulsion is found in weak or strong polyelectrolyte brushes. Polyzwitterionic brushes swell to a greater extent than the quaternized brushes studied. However, for RH levels beyond 70%, the polyzwitterionic brushes take up less water molecules, leading to a decline in water volume fraction from the maximum of 鈭?.30 down to 鈭?.10. Using a gradient in polymer chain grafting density (蟽), we provide evidence that this behavior stems from the formation of inter- and intramolecular zwitterionic complexes.