Conformation and molecular dynamics of single polystyrene chain confined in coordination nanospace.
Conformation and molecular dynamics of single polystyrene chain confined in coordination nanospace.
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DOI：
10.1021/ja800087s
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发表时间：
2008-05
影响因子：
15
通讯作者：
T. Uemura;S. Horike;Kana Kitagawa;M. Mizuno;K. Endo;S. Bracco;A. Comotti;P. Sozzani;M. Nagaoka-M.-Nagaok
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文献类型：
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作者：
T. Uemura;S. Horike;Kana Kitagawa;M. Mizuno;K. Endo;S. Bracco;A. Comotti;P. Sozzani;M. Nagaoka-M.-Nagaok
由于形成了特定的分子组装体和构象，被限制在纳米空间中的分子将具有与体相状态下的分子明显不同的性质。研究了聚苯乙烯（PSt）单链在多孔配位聚合物[Zn2（bdc）2ted] n（1; bdc = 1，4-苯二甲酸酯，ted =三亚乙基二胺）一维纳米孔道中的构象和动力学.通过二维（2D）杂波（1）H-（13）C NMR的表征给出了纳米复合材料形成和PSt与1的孔表面之间的亲密度的直接证明。复合材料的量热分析没有揭示任何PSt的玻璃化转变，这说明了与散装PSt相比，封装在纳米通道中的PSt的不同性质。从N2吸附测量，在纳米通道中的PSt的表观密度估计为0.55 g cm（-3），这是远远低于散装PSt。复合物的固态（2）H NMR研究的结果显示苯基翻转的均匀移动性具有显著低的活化能，这是由于单个PSt链封装在一维规则结晶纳米通道中。这也得到了分子动力学（MD）模拟的支持。
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 [Zn 2(bdc) 2ted] n ( 1; bdc = 1,4-benzenedicarboxylate, ted = triethylenediamine). Characterization by two-dimensional (2D) heteronuclear (1)H- (13)C 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 N 2 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 (2)H 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.