Hydration States of Poly(N-isopropylacrylamide) and Poly(N,N-diethylacrylamide) and Their Monomer Units in Aqueous Solutions with Lower Critical Solution Temperatures Studied by I

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• 作者：Chihiro Hashimoto ; Akiyoshi Nagamoto ; Takashi Maruyama ; Naomi Kariyama ; Yuma Irisa ; Akifumi Ikehata ; Yukihiro Ozaki
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：February 12, 2013
• 年：2013
• 卷：46
• 期：3
• 页码：1041-1053
• 全文大小：1010K
• 年卷期：v.46,no.3(February 12, 2013)
• ISSN：1520-5835

文摘

The coil-to-globule transition of poly(N-isopropylacrylamide) (PNiPA) and poly(N,N-diethylacrylamide) (PdEA) in aqueous solutions has recently received substantial interest in its drastic change in the hydration state from a hydrated random coil to a hydrophobic globule for practical applications: drug delivery and tissue engineering. In this report, the hydration states of PNiPA and PdEA in aqueous solutions were investigated by IR spectroscopy in the amide I, N鈥揌 and C鈥揌 stretching band regions as compared with those of their repeat units, N-isopropylpropionamide (NiPP) and N,N-diethylpropylacrylamide (dEP) in aqueous and cyclohexane solutions in combined with their phase diagrams. The IR spectral changes in the amide I and C鈥揌 stretching band regions of N-alkylamides and N,N-dialkylamides including NiPP and dEP in aqueous solutions with varying concentration was characteristic due to different amide鈥揳mide interaction; the amide鈥揳mide interaction for N-alkylamide (C鈺怬路路路H鈥揘 hydrogen bond) is stronger than that for N,N-dialkylamide (dipolar interaction). It is found that almost all amide groups of PNiPA in aqueous solution forms the intramolecular C鈺怬路路路H鈥揘 hydrogen bond even in the coil state and that the amide group of PNiPA is less hydrated than that of PdEA in spite of the similar degree of hydration to alkyl groups. The IR spectral changes in the amide I and C鈥揌 stretching band regions of PNiPA and PdEA in aqueous solutions with heat are ascribed to the dehydration of the amide and alkyl groups from the coil state to the globule one.