Kruteva M, Monkenbusch M, Allgaier J, Holderer O, Pasini S, Hoffmann I, Richter D
Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science (JCNS), 52425 Jülich, Germany.
Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at MLZ, Lichtenbergstraße 1, 85748 Garching, Germany.
Phys Rev Lett. 2020 Dec 4;125(23):238004. doi: 10.1103/PhysRevLett.125.238004.
This work clarifies the self-similar dynamics of large polymer rings using pulsed-field gradient nuclear magnetic resonance and neutron spin echo spectroscopy. We find center of mass diffusion taking place in three dynamic regimes starting (i) with a strongly subdiffusive domain ⟨r^{2}(t)⟩{com}∼t^{α} (0.4≤α≤0.65); (ii) a second subdiffusive region ⟨r^{2}(t)⟩{com}∼t^{0.75} that (iii) finally crosses over to Fickian diffusion. While the t^{0.75} range previously has been found in simulations and was predicted by theory, we attribute the first to the effect of cooperative dynamics resulting from the correlation hole potential. The internal dynamics at scales below the elementary loop size is well described by ring Rouse motion. At larger scales the dynamics is self-similar and follows very well the predictions of the scaling models with preference for the self-consistent fractal loopy globule model.
这项工作利用脉冲场梯度核磁共振和中子自旋回波光谱法阐明了大型聚合物环的自相似动力学。我们发现质心扩散发生在三种动力学区域，开始时（i）是一个强次扩散区域〈r²(t)〉com∼t^α（0.4≤α≤0.65）；（ii）第二个次扩散区域〈r²(t)〉com∼t^0.75，（iii）最终转变为菲克扩散。虽然之前在模拟中发现了t^0.75范围且理论也有预测，但我们将第一个区域归因于相关空穴势导致的协同动力学效应。低于基本环尺寸尺度的内部动力学可用环Rouse运动很好地描述。在较大尺度下，动力学是自相似的，并且非常符合标度模型的预测，尤其偏向自洽分形环球状模型。
