Department of Chemical Physics and Hefei National Laboratory for Physical Sciences at Microscales, iChEM, University of Science and Technology of China, Hefei, Anhui 230026, China.
J Chem Phys. 2018 Dec 28;149(24):244906. doi: 10.1063/1.5078419.
We study the dynamic separation process of two identical polymers confined in a cylinder, allowing both ends of the polymer chains to be free, based on a three dimensional (3D) free energy landscape combined with direct molecular dynamics (MD) simulations. The landscape suggests that the probability distribution curves of induction time (segregation time) reduced by corresponding average values would collapse into a single one under the so-called , i.e., ≡ is a constant, where is the number of monomers in a chain, is the channel diameter, and ≃ 3/5. Such a collapse behavior is well demonstrated by direct MD simulations and further by Brownian dynamics simulations of an effective particle on the 3D landscape. Interestingly, Brownian dynamics shows that the average induction time or segregation time decreases monotonically with in a power-law dependence if the diffusion coefficient is fixed, suggesting a distinct mechanism of the induction process which is neither diffusion nor barrier-crossing, in accordance with trajectory analysis by using MD simulations. In addition, we find that both and show good power-law dependencies on the polymer length under the .
我们基于一个三维（3D）自由能景观并结合直接分子动力学（MD）模拟，研究了两种相同聚合物在圆柱体中的动态分离过程，允许聚合物链的两端自由。景观表明，感应时间（分离时间）的概率分布曲线经过相应的平均值后，在所谓的下会坍缩成一个单一的曲线，即，其中 ≡ 是一个常数， 是链中的单体数， 是通道直径， ≃ 3/5。这种坍缩行为通过直接 MD 模拟得到了很好的证明，并通过在 3D 景观上对有效粒子的布朗动力学模拟进一步得到了证明。有趣的是，布朗动力学表明，如果扩散系数 固定，平均感应时间 或分离时间 随着 的单调减小呈幂律关系，这表明感应过程的机制既不是扩散也不是势垒穿越，这与使用 MD 模拟进行轨迹分析的结果一致。此外，我们发现，在 下， 和 都表现出良好的幂律依赖于聚合物长度 。
