Sissa (Scuola Internazionale Superiore di Studi Avanzati), Via Bonomea 265, 34136 Trieste, Italy.
J Chem Phys. 2018 May 21;148(19):194902. doi: 10.1063/1.5022446.
We employ large-scale molecular dynamics computer simulations to study the problem of nanoprobe diffusion in entangled solutions of linear polymers and unknotted and unconcatenated circular (ring) polymers. By tuning both the diameter of the nanoprobe and the density of the solution, we show that nanoprobes of diameter smaller than the entanglement distance (tube diameter) of the solution display the same (Rouse-like) behavior in solutions of both polymer architectures. Instead, nanoprobes with larger diameters appear to diffuse markedly faster in solutions of rings than in solutions of linear chains. Finally, by analysing the distribution functions of spatial displacements, we find that nanoprobe motion in rings' solutions shows both Gaussian and ergodic behaviors, in all regimes considered, while, in solutions of linear chains, nanoprobes exceeding the size of the tube diameter show a transition to non-Gaussian and non-ergodic motion. Our results emphasize the role of chain architecture in the motion of nanoprobes dispersed in polymer solutions.
我们采用大规模分子动力学计算机模拟方法，研究了纳米探针在线性聚合物和无纽结无拼接的圆形（环形）聚合物的纠缠溶液中的扩散问题。通过调节纳米探针的直径和溶液的密度，我们发现在溶液的两种聚合物结构中，直径小于溶液缠结距离（管直径）的纳米探针表现出相同的（类似 Rouse 的）行为。相反，直径较大的纳米探针在环形溶液中的扩散速度明显快于线性链溶液中的扩散速度。最后，通过分析空间位移分布函数，我们发现纳米探针在环形溶液中的运动在所有考虑的范围内都表现出高斯和遍历行为，而在线性链溶液中，直径超过管直径的纳米探针表现出向非高斯和非遍历运动的转变。我们的研究结果强调了链结构在聚合物溶液中分散的纳米探针运动中的作用。
