Reaction-Induced Self-Assembly of Gel Structure: A New Insight into Chemical Gelation Process of N-Isopropylacrylamide as Studied by Two-Dimensional Infrared Correlation Spectroscopy

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• 作者：Yeonju Park ; Chihiro Hashimoto ; Takeji Hashimoto ; Yoshitsugu Hirokawa ; Young Mee Jung ; Yukihiro Ozaki
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：May 14, 2013
• 年：2013
• 卷：46
• 期：9
• 页码：3587-3602
• 全文大小：1110K
• 年卷期：v.46,no.9(May 14, 2013)
• ISSN：1520-5835

文摘

We report a new insight into the chemical gelation process of poly(N-isopropylacrylamide) (PNiPAAm) hydrogel elucidated on the basis of the in situ observations with time-resolved Fourier-transform infrared spectroscopy (FTIR), its principal component analysis (PCA), and two-dimensional correlation spectroscopy (2D COS) at preparation temperatures below and above the lower critical solution temperature of PNiPAAm aqueous solution. First, we spectroscopically identified for the first time the specific time-spans for the two-stage reaction process: the first-stage giving rise to linear and branched random copolymers of NiPAAm and cross-linker monomers and the second-stage giving rise to cross-linking into macroscopic network structure. Second, we conducted 2D COS for both the first-stage and second-stage reaction processes in order to resolve highly superposed spectra in the amide I and II regions into fundamental spectra comprising the superposed spectra. We elucidated the time-sequence order of the changes in the fundamental spectra occurring in situ during the gelation process. We proposed molecular interpretations of the sequence of the spectroscopic events, which would give deep insights into molecular mechanisms of the gelation process as detailed in the text.