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The Effect of the End Segments on the Dynamics of a Polymer Melt: The Frequency Nature of the Effect and Possibility of Experimental Observation in the Free Induction Decay of Deuterons
Polymer Science, Series A ( IF 1 ) Pub Date : 2020-04-06 , DOI: 10.1134/s0965545x20020030
I. K. Ostrovskaya , N. F. Fatkullin

Abstract

It is shown that, in the melts of linear macromolecules, the effects of dynamic heterogeneity associated with the presence of end segments are not vanishingly small in the limit \(N \to \infty \), where \(N\) is the number of Kuhn segments in the macromolecule. The effect has a frequency nature, i.e., the division of the segments into “end” ones, more mobile in comparison with the “median” ones, mainly depends on the observation time. With the increase in the observation time, symmetrical growth of the “end” regions of the polymer chain occurs from both ends of the macromolecule which covers the entire macromolecule at times on the order of the terminal relaxation time. The effect generates nontrivial experimentally observed consequences. For example, the free induction decay of deuterons in monodisperse polymer melts of macromolecules should have an extended region with the exponential decay law \(g(t) \propto {{t}^{{ - \beta }}}\), where \(\beta = 1\) for the reptation model and \(\beta = {{(\alpha - 2)}^{{ - 1}}}\) for isotropic renormalized Rouse models: \(\alpha > 2\) is the exponent of the molecular weight dependence of the terminal relaxation time of macromolecules. At \(\alpha \leqslant 2\), the influence of the effects of dynamic heterogeneity on the shape of free induction decay is weaker, although it is observable at sufficient accuracy of the measurements.



中文翻译:

末端片段对聚合物熔体动力学的影响:氘核自由感应衰变的频率效应和实验观察的可能性

摘要

结果表明,在线性大分子的熔体中,与端段的存在相关的动态异质性的影响不会在极限\(N \ to \ infty \)中消失,其中\(N \)是大分子中的库恩片段数。效果具有频率性质,即将段划分为“端”段(与“中”段相比更具移动性)主要取决于观察时间。随着观察时间的增加,聚合物链“末端”区域的对称生长从大分子的两端开始,该末端有时覆盖整个大分子,大约是末端弛豫时间的量级。这种效果会产生非平凡的实验观察到的结果。例如,氘在大分子单分散聚合物熔体中的自由感应衰变应具有指数衰减定律\(g(t)\ propto {{t} ^ {{-\ beta}}} \)的扩展区域,其中\(\ beta = 1 \)用于复制模型,各向同性重归一化的Rouse模型的\(\ beta = {{((alpha-2)} ^ {{-1}}} \)\(\ alpha> 2 \)是末端弛豫的分子量依赖性指数大分子的时间。在\(\ alpha \ leqslant 2 \)处,尽管可以在足够的测量精度下观察到,但动态异质性对自由感应衰减形状的影响较弱。

更新日期:2020-04-06
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