Chain Confinement and Anomalous Diffusion in the Cross over Regime between Rouse and Reptation,ACS Macro Letters

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Chain Confinement and Anomalous Diffusion in the Cross over Regime between Rouse and Reptation
ACS Macro Letters ( IF 5.1 ) Pub Date : 2022-11-21 , DOI: 10.1021/acsmacrolett.2c00608
Aakash Sharma ₁ , Margarita Kruteva ₁ , Jürgen Allgaier ₁ , Ingo Hoffmann ₂ , Peter Falus ₂ , Michael Monkenbusch ₁ , Dieter Richter ₁

Affiliation

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 ⟨r_com²(t)⟩ 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 ⟨r_com²(t)⟩, we experimentally found the subdiffusive regime with an exponent close to

μ = \frac{1}{2}

, which, however, crosses over to Fickian diffusion not at the Rouse time, but at a later time, when the ⟨r_com²(t)⟩ has covered a distance related to the tube diameter.

中文翻译：

Rouse 和 Reptation 交叉机制中的链限制和异常扩散

通过中子自旋回波 (NSE) 和脉冲场梯度 (PFG) NMR，我们研究了聚环氧乙烷熔体 (PEO) 的动力学，其分子量处于 Rouse 和蠕动动力学之间的过渡状态。我们使用允许减少长波长 Rouse 模式振幅的 Rouse 模式分析数据。对于短时间，允许次扩散质心均方位移 ⟨ r _com² ( t )⟩。这种方法可以很好地捕获 NSE 数据，并提供有关链长范围内拓扑约束的准确信息，而管模型不适用。正如聚合物蠕动所预测的那样 ⟨ r _com² ( t)⟩，我们通过实验发现了指数接近于