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首页> 外文期刊>Macromolecules >STRUCTURE, CONFORMATION, AND MOTIONS OF POLY(ETHYLENE OXIDE) AND POLY(ETHYLENE GLYCOL) IN THEIR UREA INCLUSION COMPOUNDS
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STRUCTURE, CONFORMATION, AND MOTIONS OF POLY(ETHYLENE OXIDE) AND POLY(ETHYLENE GLYCOL) IN THEIR UREA INCLUSION COMPOUNDS

机译：尿素包合物中聚环氧乙烷和聚乙二醇的结构，构型和运动

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X-ray diffraction and FTIR and C-13 NMR spectroscopies have been utilized to observe the inclusion compounds (ICs) formed by poly(ethylene oxide) (PEG) and low molecular weight poly(ethylene glycol) (PEG) oligomer with urea (U). We have confirmed that PEO-U-IC formed from solution has a trigonal crystal structure, while recrystallization from the melt produces a hexagonal PEO-U-IC. PEG-U-IC apparently adopts a crystal structure different from the trigonal and hexagonal forms of PEO-U-IC, and single crystals of PEG-U-IC are currently under investigation by X-ray diffraction. The conformations of PEG. and PEG chains in their U-ICs appear similar to the TGT bulk crystalline conformation, while the all-trans conformer does not appear to be consistent with either the FTIR or the C-13 NMR observations. For solution-formed PEO-U-IC in the trigonal crystal structure, where one-third of the urea molecules are hydrogen-bonded to the PEO chains and reside in the channels, the mobility of the included PEO chains is similar to that of the bulk crystalline PEG. This is quite different from the usual observations made on hexagonal polymer-U-ICs, where spin-lattice relaxation times observed for the carbon atoms of the included polymers are much reduced (often more than 1 order of magnitude) from those observed for the same polymer in their bulk crystals. It is proposed that the direct involvement of the urea molecules in the trigonal channels of PEO-U-IC with the included PEO chains is the source of their reduced mobility. [References: 26]
机译：X射线衍射，FTIR和C-13 NMR光谱学已用于观察由聚环氧乙烷（PEG）和低分子量聚（乙二醇）（PEG）低聚物与尿素（U）形成的夹杂物（IC） ）。我们已经确认，由溶液形成的PEO-U-IC具有三角形晶体结构，而从熔体中重结晶会产生六边形PEO-U-IC。 PEG-U-IC显然采用不同于PEO-U-IC的三角形和六边形形式的晶体结构，目前正在通过X射线衍射研究PEG-U-IC的单晶。 PEG的构象。它们的U-IC中的PEG和PEG链看起来与TGT的整体晶体构象相似，而全反式构象与FTIR或C-13 NMR观察都不一致。对于在三角形晶体结构中溶液形成的PEO-U-IC，其中三分之一的尿素分子氢键合到PEO链上并驻留在通道中，所包含的PEO链的迁移率类似于块状结晶PEG。这与对六角形聚合物-U-IC的常规观察结果有很大不同，在常规观察中，所观察到的所含聚合物碳原子的自旋晶格弛豫时间比相同聚合物所观察到的显着减少（通常超过1个数量级）。聚合物的块状晶体。提出尿素分子直接参与具有所包含的PEO链的PEO-U-IC的三角通道中是其降低的迁移率的来源。 [参考：26]

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