Kivotides Demosthenes, Wilkin S Louise, Theofanous Theo G
Department of Chemical Engineering, Center for Risk Studies and Safety, University of California, Santa Barbara, California 93117, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Oct;80(4 Pt 1):041808. doi: 10.1103/PhysRevE.80.041808. Epub 2009 Oct 29.
We formulate a coarse-grained molecular-dynamics model of polymer chains in solution that includes hydrodynamic interactions, thermal fluctuations, nonlinear elasticity, and topology-preserving solvent mediated excluded volume interactions. The latter involve a combination of potential forces with explicit geometric detection and tracking of chain entanglements. By solving this model with numerical and computational methods, we study the physics of polymer knots in a strong extensional flow (Deborah number De=1.6 ). We show that knots slow down the stretching of individual polymers by obstructing via entanglements the "natural," unraveling, and flow-induced chain motions. Moreover, the steady-state polymer length and polymer-induced stress values are smaller in knotted chains than in topologically trivial chains. We indicate the molecular processes via which the rate of knot tightening affects the rheology of the solution.
我们构建了一个溶液中聚合物链的粗粒化分子动力学模型，该模型包括流体动力学相互作用、热涨落、非线性弹性以及拓扑保持溶剂介导的排除体积相互作用。后者涉及势能与链缠结的显式几何检测和跟踪的组合。通过用数值和计算方法求解该模型，我们研究了强拉伸流（德博拉数De = 1.6）中聚合物结的物理性质。我们表明，结通过缠结阻碍单个聚合物的“自然”解缠和流动诱导的链运动，从而减缓了聚合物的拉伸。此外，打结链中的稳态聚合物长度和聚合物诱导的应力值比拓扑平凡链中的要小。我们指出了结收紧速率影响溶液流变学的分子过程。
