Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States.
Institute of Physics, Johannes Gutenberg University Mainz , Staudingerweg 7, 55128 Mainz, Germany.
Langmuir. 2017 Apr 18;33(15):3685-3693. doi: 10.1021/acs.langmuir.7b00543. Epub 2017 Apr 6.
Stratification in binary colloidal mixtures was investigated using implicit-solvent molecular dynamics simulations. For large particle size ratios and film Péclet numbers greater than unity, smaller colloids migrated to the top of the film, while big colloids were pushed to the bottom, creating an "inverted" stratification. This peculiar behavior was observed in recent simulations and experiments conducted by Fortini et al. [ Phys. Rev. Lett. 2016 , 116 , 118301 ]. To rationalize this behavior, particle size ratios and drying rates spanning qualitatively different Péclet number regimes were systematically studied, and the dynamics of the inverted stratification were quantified in detail. The stratified layer of small colloids was found to grow faster and to larger thicknesses for larger size ratios. Interestingly, inverted stratification was observed even at moderate drying rates where the film Péclet numbers were comparable to unity, but the thickness of the stratified layer decreased. A model based on dynamical density functional theory is proposed to explain the observed phenomena.
使用隐溶剂分子动力学模拟研究了二元胶体混合物的分层现象。对于较大的颗粒尺寸比和大于 1 的膜佩克莱数，较小的胶体迁移到膜的顶部，而较大的胶体被推到底部，形成了一种“倒置”的分层。这种特殊的行为在 Fortini 等人最近的模拟和实验中观察到。[物理评论快报。2016 年，116 期，118301]。为了解释这种行为，系统地研究了跨越定性不同佩克莱数区域的颗粒尺寸比和干燥速率，并详细量化了倒置分层的动力学。发现小胶体的分层层在较大的尺寸比下生长得更快，厚度更大。有趣的是，即使在干燥速率适中的情况下，即膜佩克莱数与 1 相当，但分层层的厚度减小，也观察到了倒置分层。提出了一个基于动力学密度泛函理论的模型来解释所观察到的现象。
