Conformation and Molecular Dynamics of Single Polystyrene Chain Confined in Coordination Nanospace

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• 作者：Takashi Uemura ; Satoshi Horike ; Kana Kitagawa ; Motohiro Mizuno ; Kazunaka Endo ; Silvia Bracco ; Angiolina Comotti ; Piero Sozzani ; Masataka Nagaoka ; Susumu Kitagawa
• 刊名：Journal of the American Chemical Society
• 出版年：2008
• 出版时间：May 28, 2008
• 年：2008
• 卷：130
• 期：21
• 页码：6781 - 6788
• 全文大小：1297K
• 年卷期：v.130,no.21(May 28, 2008)
• ISSN：1520-5126

文摘

Molecules confined in nanospaces will have distinctly different properties to those in the bulk state because of the formation of specific molecular assemblies and conformations. We studied the chain conformation and dynamics of single polystyrene (PSt) chains confined in highly regular one-dimensional nanochannels of a porous coordination polymer [Zn₂(bdc)₂ted]_n (1; bdc = 1,4-benzenedicarboxylate, ted = triethylenediamine). Characterization by two-dimensional (2D) heteronuclear ¹H−¹³C NMR gave a direct demonstration of the nanocomposite formation and the intimacy between the PSt and the pore surfaces of 1. Calorimetric analysis of the composite did not reveal any glass transition of PSt, which illustrates the different nature of the PSt encapsulated in the nanochannels compared with that of bulk PSt. From N₂ adsorption measurements, the apparent density of PSt in the nanochannel was estimated to be 0.55 g cm⁻³, which is much lower than that of bulk PSt. Results of a solid-state ²H NMR study of the composite showed the homogeneous mobility of phenyl flipping with significantly low activation energy, as a result of the encapsulation of single PSt chains in one-dimensional regular crystalline nanochannels. This is also supported by molecular dynamics (MD) simulations.