Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science (JCNS-1: Neutron Scattering and Biological Matter), 52425Jülich, Germany.
Institut Max von Laue-Paul Langevin (ILL), 71 avenue des Martyrs, CS 20156, Cedex 9, F-38042Grenoble, France.
ACS Macro Lett. 2022 Dec 20;11(12):1343-1348. doi: 10.1021/acsmacrolett.2c00608. Epub 2022 Nov 21.
By neutron spin echo (NSE) and pulsed field gradient (PFG) NMR, we study the dynamics of a polyethylene-oxide melt (PEO) with a molecular weight in the transition regime between Rouse and reptation dynamics. We analyze the data with a Rouse mode analysis allowing for reduced long wavelength Rouse modes amplitudes. For short times, subdiffusive center-of-mass mean square displacement ⟨()⟩ was allowed. This approach captures the NSE data well and provides accurate information on the topological constraints in a chain length regime, where the tube model is inapplicable. As predicted by reptation for the polymer ⟨()⟩, we experimentally found the subdiffusive regime with an exponent close to , which, however, crosses over to Fickian diffusion not at the Rouse time, but at a later time, when the ⟨()⟩ has covered a distance related to the tube diameter.
通过中子自旋回波（NSE）和脉冲梯度场（PFG）NMR，我们研究了分子量处于罗瑟和蠕动动力学转变区的聚氧化乙烯熔体（PEO）的动力学。我们使用允许降低长波长罗瑟模式振幅的罗瑟模式分析来分析数据。对于短时间，允许中心质量均方位移 ⟨()⟩的亚扩散。这种方法很好地捕捉了 NSE 数据，并提供了有关在管模型不适用的链长范围内拓扑约束的准确信息。正如聚合物 ⟨()⟩的蠕动所预测的那样，我们实验发现了具有接近 ⁇ 的亚扩散区，然而，这种扩散不是在罗瑟时间而是在后来的时间，当 ⟨()⟩已经覆盖了与管直径相关的距离时，才会跨越到菲克扩散。
