Andreev Marat, Prabhu Vivek M, Douglas Jack F, Tirrell Matthew, de Pablo Juan J
Institute of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States.
National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
ACS Macro Lett. 2018;51. doi: 10.1021/acs.macromol.8b00556.
Complex coacervation refers to the formation of distinct liquid phases that arise when polyelectrolytes are mixed under appropriate polymer and salt concentrations. Molecular-level studies of coacervation have been limited. In this work, a coarse-grained model of the polymers and the corresponding counterions is proposed and used to simulate coacervation as a function of polymer length and overall salt concentration. Several sampling methods are used to determine the phase behavior of the underlying polymers. In particular, the results of simulations in different ensembles are shown to be consistent and to reproduce a number of phenomena observed in experiments, including the disruption of complexation by increasing ionic strength or by decreasing molecular weight. The coacervate concentrations determined from phase behavior calculations are then used to examine the rheology of the corresponding materials. By relying on long dynamic simulations, we are able to generate the dynamic response of the material in the form of dynamic moduli as a function of frequency, which are also found to compare favorably with experimental measurements.
复合凝聚是指当聚电解质在适当的聚合物和盐浓度下混合时出现的不同液相的形成。对凝聚的分子水平研究一直很有限。在这项工作中，提出了聚合物和相应抗衡离子的粗粒度模型，并用于模拟凝聚过程作为聚合物长度和总盐浓度的函数。使用了几种采样方法来确定基础聚合物的相行为。特别是，不同系综中的模拟结果显示是一致的，并且再现了实验中观察到的许多现象，包括通过增加离子强度或降低分子量来破坏络合作用。然后，根据相行为计算确定的凝聚层浓度用于研究相应材料的流变学。通过依赖长时间的动态模拟，我们能够以动态模量作为频率的函数的形式生成材料的动态响应，并且发现这些动态响应与实验测量结果也具有良好的可比性。
