Local and cooperative motions at the glass transition of polystyrene : information from one- and two-dimensional NMR as compared with other techniques
Local and cooperative motions at the glass transition of polystyrene : information from one- and two-dimensional NMR as compared with other techniques
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聚苯乙烯玻璃化转变中的局部和协同运动：与其他技术相比，来自一维和二维 NMR 的信息
DOI：
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发表时间：
1991
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：
U. Pschorn;E. Roessler;H. Sillescu;S. Kaufmann;D. Schaefer;H. Spiess
2 H NMR的结果进行了分析，在不同的重取向模型应用到链氘代聚苯乙烯的C− 2 H键方向。主导的机制是旋转扩散的小角度的步骤，平均旋转相关时间agress与弛豫时间从动态力学实验超过10个十年的动态范围。比较了研究链条运动的不同方法的结果。结果表明，NMR探测到的运动或明确定义的C-H键方向与α-过程的协同运动紧密耦合。此外，通过从熔体冷却，还监测了当接近Tg时，快β过程与慢α过程的分离
2 H NMR results are analyzed in terms of different reorientation models applied to the C− 2 H bond directions of chain-deuterated polystyrene. The dominant mechanism is rotational diffusion by small angular steps where the mean rotational correlation time agress with relaxation times from dynamic mechanical experiments over a dynamic range of 10 decades. The results of the different methods employed fopr the study of chain motion are compared. It is shown that the motions or well-defined C−H bond directions which are probed by NMR are tightly coupled to the cooperative motion of the α-process. moreover, the also monitor the separation of the fast β-process from the slow α-process when approaching T g by colling down from the melt