Determination of End-to-End Distances in Oligomers by Pulsed EPR
Determination of End-to-End Distances in Oligomers by Pulsed EPR
复制标题
通过脉冲 EPR 测定低聚物的端到端距离
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
H. Spiess
中科院分区：
文献类型：
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作者：
V. Pfannebecker;H. Klos;M. Hubrich;T. Volkmer;A. Heuer;U. Wiesner;H. Spiess
用脉冲双电子-电子共振（DEER）方法研究了末端标记烷烃在刚性聚合物基体中的构象。为此，在聚苯乙烯基质中记录了一系列具有8−20个亚甲基单元和链端用氮氧自由基双官能化的脂肪族二碳酸的偶极光谱。双自由基衍生自受阻胺光稳定剂（HALS），用作聚合物添加剂。偶极光谱的分析允许测定低聚物双自由基的端到端距离。实验表明，“柔性”烷烃链几乎完全伸展。这一观察结果与力场计算的结果一致。
Conformations of end-labeled alkanes in a rigid polymer matrix were investigated using the pulsed double electron-electron resonance (DEER) method. To this end, dipolar spectra of a series of aliphatic dicarbonic acids with 8−20 methylene units and chain ends bifunctionalized with nitroxide radicals were recorded in a polystyrene matrix. The biradicals are derived from hindered amine light stabilizers (HALS), used as polymer additives. Analysis of the dipolar spectra allows the determination of the end-to-end distances of the oligomer biradicals. The experiments show that the “flexible” alkane chains are almost completely stretched. This observation is consistent with the results of force field calculations.