Institut Laue-Langevin, 71 Rue des Martyrs, 38000 Grenoble, France.
Division for Material Physics, Department for Physics and Astronomy, Lägerhyddsvägen 1, 752 37 Uppsala, Sweden.
J Chem Phys. 2018 Aug 21;149(7):074901. doi: 10.1063/1.5035170.
The non-linear response of entangled polymers to shear flow is complicated. Its current understanding is framed mainly as a rheological description in terms of the complex viscosity. However, the full picture requires an assessment of the dynamical structure of individual polymer chains which give rise to the macroscopic observables. Here we shed new light on this problem, using a computer simulation based on a blob model, extended to describe shear flow in polymer melts and semi-dilute solutions. We examine the diffusion and the intermediate scattering spectra during a steady shear flow. The relaxation dynamics are found to speed up along the flow direction, but slow down along the shear gradient direction. The third axis, vorticity, shows a slowdown at the short scale of a tube, but reaches a net speedup at the large scale of the chain radius of gyration.
纠缠聚合物对剪切流动的非线性响应很复杂。目前的理解主要是从复杂粘度的角度来描述流变学。然而，完整的图景需要评估导致宏观可观测现象的单个聚合物链的动态结构。在这里，我们使用基于斑点模型的计算机模拟来解决这个问题，该模型扩展到描述聚合物熔体和半稀溶液中的剪切流动。我们在稳态剪切流中研究扩散和中间散射谱。发现松弛动力学沿流动方向加速，但沿剪切梯度方向减速。第三个轴，涡度，在管的小尺度上减速，但在链回转半径的大尺度上达到净加速。
