Solvation Energy of Ions in Polymers: Effects of Chain Length and Connectivity on Saturated Dipoles near Ions.
Solvation Energy of Ions in Polymers: Effects of Chain Length and Connectivity on Saturated Dipoles near Ions.
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DOI：
10.1021/acs.jpcb.7b00671
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发表时间：
2017-04
期刊：
影响因子：
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通讯作者：
Lijun Liu;I. Nakamura
中科院分区：
文献类型：
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作者：
Lijun Liu;I. Nakamura
我们通过开发一种新的粗粒度分子动力学模拟来说明链连通性对聚合物液体中离子溶剂化能的影响。我们的理论通过偶极单体单元与非线性弹簧的连接来解释聚合物的介电响应。与标准离子的波恩溶剂化能形成鲜明对比的是，我们的结果在很大程度上取决于聚合物的链长。我们还证明了离子浸入非聚合物颗粒混合物、单组分聚合物、聚合物共混物和嵌段共聚物中的溶剂化能的显著差异。因此，我们认为聚合物的链结构是离子溶剂化的关键因素，而这一特征在主要的理论和模拟文献中往往没有得到充分的考虑。当偶极矩相对较小时，我们的结果与先前的粗粒平均场理论预测的结果一致。然而，我们也证明了强离子-偶极子和偶极子-偶极子相互作用导致单体单元的链状结合，导致平均场理论和模拟之间的定性差异。这种强的静电相关性可以逆转聚合物中离子的溶剂化能对链长的依赖性。
We illustrate the effects of chain connectivity on the solvation energy of ions immersed in polymer liquids by developing a new coarse-grained molecular dynamics simulation. Our theory accounts for the dielectric response of the polymers through the connection of dipolar, monomeric units with nonlinear springs. In stark contrast to the standard Born solvation energy of ions, our results depend substantially on the chain length of the polymers. We also demonstrate the marked difference in the solvation energies of the ions immersed in non-polymeric particle mixtures, single-component polymers, polymer blends, and block copolymers. Thus, we suggest that the chain architecture of polymers is a key factor in ion solvation, whereas this feature is often inadequately considered in main theory and simulation literature. Our results are consistent with those predicted by previous coarse-grained mean-field theories when the dipole moment of the polymer compositions is relatively small. However, we also demonstrate that the strong ion-dipole and dipole-dipole interactions cause the chain-like association of the monomeric units, resulting in a qualitative discrepancy between the mean-field theory and simulation. Such a strong electrostatic correlation may reverse the dependence of the chain length on the solvation energy of the ions in the polymers.