The discrete slip-link theory is a hierarchy of strongly connected models that have great success predicting the linear and nonlinear rheology of high-molecular-weight polymers. Three of the four parameters of the most-detailed model, which can be extracted from primitive-path analysis, give quantitative agreement with experimental data for all examined chemistries (polystyrene, polyisoprene, polybutadiene, and polyethylene). Here, we attempt to extract the remaining friction parameter from atomistic simulations. In particular, an available quantum chemistry-based force field for polyethylene oxide (PEO) was used to perform molecular-dynamics simulations of a 12 kDa melt. The Kuhn friction is obtained from the mean-squared displacement of the center-of-mass of the chains (MSD of COM) in the melt. The result is also corroborated using the relaxation modulus calculated through the Green–Kubo formula. Once the four parameters are determined for any chemistry, all parameters for all members of the slip-link hierarchy are determined. Then, using a coarser member of the hierarchy, the dynamic modulus of a 256 kDa PEO melt was predicted. The predictions are compared to experimental measurements performed at the same temperature. Unfortunately, the extracted friction is about 30% larger than the one observed in the experiment. However, two fundamentally different methods, one utilizing the MSD of COM and the other the relaxation modulus, gave consistent results for the extracted Kuhn friction. Therefore, the discrepancy presumably arises from insufficient accuracy in the force field. Nonetheless, the work demonstrates that theory predictions without adjustable parameters should be possible.

中文翻译：

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使用滑动连接模型从第一原理预测聚合物流变学

离散滑动连接理论是一个强连接模型的层次结构，在预测高分子量聚合物的线性和非线性流变学方面取得了巨大成功。可以从原始路径分析中提取的最详细模型的四个参数中的三个与所有检查的化学物质（聚苯乙烯、聚异戊二烯、聚丁二烯和聚乙烯）的实验数据定量一致。在这里，我们尝试从原子模拟中提取剩余的摩擦参数。特别是，聚环氧乙烷 (PEO) 的可用基于量子化学的力场用于执行 12 kDa 熔体的分子动力学模拟。库恩摩擦是从熔体中链（COM 的 MSD）的质心的均方位移获得的。使用通过 Green-Kubo 公式计算的松弛模量也证实了该结果。一旦确定了任何化学的四个参数，就确定了滑动链接层次结构中所有成员的所有参数。然后，使用层次结构中较粗的成员，预测 256 kDa PEO 熔体的动态模量。将预测结果与在相同温度下进行的实验测量进行比较。不幸的是，提取的摩擦力比实验中观察到的摩擦力大约 30%。然而，两种根本不同的方法，一种利用 COM 的 MSD，另一种利用松弛模量，对提取的库恩摩擦给出了一致的结果。因此，这种差异可能是由于力场精度不足造成的。尽管如此，