pH-responsive behavior of selectively quaternized diblock copolymers adsorbed at the silica/aqueous solution interface

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• 作者：Kenichi Sakai ; Emelyn G. Smith ; Grant B. Webber ; Murray Baker ; Erica J. Wanless ; Vural Bü ; tü ; n ; Steven P. Armes ; Simon Biggs
• 关键词：pH-responsive diblock copolymer ; Adsorption ; Desorption ; Quaternization
• 刊名：Journal of Colloid and Interface Science
• 出版年：2007
• 出版时间：15 October 2007
• 年：2007
• 卷：314
• 期：2
• 页码：381-388
• 全文大小：219 K

文摘

The desorption and subsequent pH-responsive behavior of selectively quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate) (PDMA–PDEA) films at the silica/aqueous solution interface has been characterized. The copolymer films were prepared at pH 9, where micelle-like surface aggregates are spontaneously formed on silica. The subsequent rinse with a copolymer-free electrolyte solution adjusted to pH 9 causes partial desorption of the weakly or non-quaternized copolymers, but negligible desorption for the highly quaternized copolymers. Further rinsing with a pH 4 electrolyte solution results in additional desorption and extension (swelling) of the remaining adsorbed copolymer film normal to the interface. This pH-responsive behavior is reversible for two pH cycles (9–4–9–4) as monitored by both quartz crystal microbalance with dissipation monitoring (QCM-D) and also ζ potential measurements. The magnitude of the pH-responsive behavior depends on the mean degree of quaternization of the PDMA block. Moreover, a combination of contact angle data, ζ potential measurements and in situ atomic force microscopy (AFM) studies indicates that the pH-responsive behavior is influenced not only by the number of cationic binding sites on the adsorbed copolymer chains but also by the adsorbed layer structure.