Salt-induced structural behavior for poly(N-isopropylacryamide) grafted onto solid surface observed directly by AFM and QCM-D

被引:52
作者
Ishida, Naoyuki
Biggs, Simon [1 ]
机构
[1] Univ Leeds, Environm & Mat Engn, Sch Process, Inst Particle Sci & Engn, Leeds LS2 9JT, W Yorkshire, England
[2] Natl Inst Adv Ind Sci & Technol, Res Inst Environm Management Technol, Tsukuba, Ibaraki 3068569, Japan
关键词
D O I
10.1021/ma071878e
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
The salt-induced structural changes of an end-grafted poly(N-isopropylacrylamide) (PNIPAM) layer on a silica substrate were investigated in sodium sulfate solutions using an atomic force microscope (AFM) and a quartz crystal microbalance with dissipation (QCM-D). A PNIPAM layer was grafted onto the silicon wafer surface by free radical polymerization of NIPAM to obtain a high molecular weight polymer layer with low grafting density overall. AFM images of the coated surface were featureless at low salt concentrations commensurate with a brush-like layer. At salt concentrations >= 0.11 M, a large number of domain structures, with a characteristic size of similar to 100 nm, were seen on the surface commensurate with a collapse of the brush-like layer into mushroom-like aggregates. This critical concentration for brush collapse is in good agreement with the concentration range of between 0.1 and 0.2 M, at which the phase transition of the bulk PNIPAM is reported. Both the frequency and the dissipation data obtained using a QCM-D also showed a significant change at this concentration indicative of the layer collapse. Further analysis of these data confirmed that the observed PNIPAM structural transition was caused by a collapse of the brush-like structure as a result of dehydration of the polymer chains.
引用
收藏
页码:9045 / 9052
页数:8
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