Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901, USA.
J Chem Phys. 2011 Feb 28;134(8):084903. doi: 10.1063/1.3556749.
Mode-coupling theory is employed to study diffusion of nanoparticles in polymer melts and solutions. Theoretical results are directly compared with molecular dynamics simulation data for a similar model. The theory correctly reproduces the effects of the nanoparticle size, mass, particle-polymer interaction strength, and polymer chain length on the nanoparticle diffusion coefficient. In accord with earlier experimental, simulation, and theoretical work, it is found that when the polymer radius of gyration exceeds the nanoparticle radius, the Stokes-Einstein relation underestimates the particle diffusion coefficient by as much as an order of magnitude. Within the mode-coupling theory framework, a microscopic interpretation of this phenomenon is given, whereby the total diffusion coefficient is decomposed into microscopic and hydrodynamic contributions, with the former dominant in the small particle limit, and the latter dominant in the large particle limit. This interpretation is in agreement with previous mode-coupling theory studies of anomalous diffusion of solutes in simple dense fluids.
采用模式耦合理论研究了纳米粒子在聚合物熔体和溶液中的扩散。将理论结果与类似模型的分子动力学模拟数据进行了直接比较。该理论正确地再现了纳米粒子尺寸、质量、粒子-聚合物相互作用强度和聚合物链长对纳米粒子扩散系数的影响。与早期的实验、模拟和理论工作一致，当聚合物回转半径超过纳米粒子半径时，Stokes-Einstein 关系会导致粒子扩散系数低估多达一个数量级。在模式耦合理论框架内，对此现象给出了微观解释，即将总扩散系数分解为微观和流体力学贡献，前者在小粒子极限下占主导地位，后者在大粒子极限下占主导地位。这一解释与先前关于简单密集流体中溶质异常扩散的模式耦合理论研究一致。
