Internal Motions of Linear Chains and Spherical Microgels in Theta and Poor Solvents
Publication in refereed journal

香港中文大學研究人員

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摘要Internal motions of narrowly poly(N-isopropylacrylamide) (PNIPAM) linear chains and spherical microgels in a very dilute aqueous solution and dispersion were studied under the Theta and poor solvent conditions by dynamic laser light scattering (LLS) over a wide range of scattering angles. As expected, only one narrow peak related to the translational diffusion was observed in the line-width distribution G(Gamma) of both linear chains and spherical microgels when x < 1, where x = (qR(g))(2) with q and R-g the scattering vector and the radius of gyration, respectively. As x increases to approach 1, we start to see a second peak related to fast internal motions of linear chains, whose average line width is related to some of the internal motions (normal modes) predicted in the nondraining bead-and-spring model. However, for swollen microgels, the second peak related to the internal motions only appears when x is much higher (1/q similar to 50 nm), indicating that thermal energy is not able to excite the entire microgel but only a small portion of the gel network. As the solvent quality changes from good to poor, the shrinking of a linear chain or subchains in the gel network gradually suppresses the internal motions, presumably due to stronger intersegment interaction. Surprisingly, we found that the relative contribution of the second peak makes a turning near the Theta temperature, leading to a new way to estimate the Theta condition of a given polymer solution.
著者Dai ZJ, Wu C
期刊名稱Macromolecules
出版年份2010
月份12
日期14
卷號43
期次23
出版社American Chemical Society
頁次10064 - 10070
國際標準期刊號0024-9297
電子國際標準期刊號1520-5835
語言英式英語
Web of Science 學科類別Polymer Science; POLYMER SCIENCE

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