Anomalous diffusion of polystyrene from an attractive substrate based on all-atom simulation
Anomalous diffusion of polystyrene from an attractive substrate based on all-atom simulation
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基于全原子模拟的聚苯乙烯从有吸引力的基材的异常扩散
DOI：
10.1039/c8cp04177f
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发表时间：
2018
影响因子：
3.3
通讯作者：
Nanrong Zhao
中科院分区：
文献类型：
--
作者：
Bingjie Zhang;Xiuli Cao;Ge Zhou;Nanrong Zhao
基于全原子模拟，研究了具有不同接枝密度 φG 的聚苯乙烯（PS）聚合物链从羟基（-OH）封端的 Si 表面的扩散。我们特别关注有吸引力的基材对 PS 的扩散和构型特性的影响。我们的模拟结果揭示了随着 phiG 的增加，聚合物扩散发生了一种非常新颖且意想不到的变化，即，在具有中等接枝密度的基材上，扩散速度最显着减慢，而在较低或完全接枝的情况下，扩散动力学甚至得到促进而不是阻碍。从能量和构象变化方面详细研究了潜在的机制。令人惊讶的是，我们获得了一致的扩散场景。在中等接枝密度下，扩散所需克服的能量较大。此外，PS 链更有可能处于拉伸构型，松弛速度较慢。这些事实可以解释扩散受阻的原因。在较低或完全接枝密度下，扩散所需的能量变得比未接枝情况更小。此外，PS 链更喜欢收缩配置，以进行更快的松弛。因此，合理地促进了PS的扩散。
The diffusion of polystyrene (PS) polymer chains from a hydroxy (–OH)-terminated Si surface with different grafting densities ϕG is studied based on all-atom simulation. Our particular attention is paid to the impact of the attractive substrate on the diffusive and configurational properties of PS. Our simulation results uncover a very novel and unexpected modification to polymer diffusion with the increment of ϕG, namely, the diffusion is slowed down most significantly from a substrate with moderate grafting densities, while in lower or full grafting cases, the diffusive dynamics is even facilitated rather than retarded. The underlying mechanism is investigated in terms of energy and conformational change in detail. Surprisingly, we obtain a consistent scenario for diffusion. Under moderate grafting densities, the energy required to be overcome for diffusion is relatively large. In addition, PS chains are more likely to be in a stretched configuration subject to a slower relaxation. These facts can account for the hindered diffusion. While under lower or full grafting densities, the energy required for diffusion becomes even smaller than the ungrafted situation. Also, PS chains prefer a shrinking configuration undergoing faster relaxation. Consequently, the diffusion of PS is reasonably promoted.