On the Behavior of the Ethylene Glycol Components of Polydisperse Polyethylene Glycol PEG200,The Journal of Physical Chemistry B

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On the Behavior of the Ethylene Glycol Components of Polydisperse Polyethylene Glycol PEG200
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2023-01-26 , DOI: 10.1021/acs.jpcb.2c06773
Markus M Hoffmann ₁ , Matthew D Too ₁ , Nathaniel A Paddock ₁ , Robin Horstmann ₂ , Sebastian Kloth ₂ , Michael Vogel ₂ , Gerd Buntkowsky ₃

Affiliation

Molecular dynamics (MD) simulations are reported for [polyethylene glycol (PEG)200], a polydisperse mixture of ethylene glycol oligomers with an average molar weight of 200 g·mol^–1. As a first step, available force fields for describing ethylene glycol oligomers were tested on how accurately they reproduced experimental properties. They were found to all fall short on either reproducing density, a static property, or the self-diffusion coefficient, a dynamic property. Discrepancies with the experimental data increased with the increasing size of the tested ethylene glycol oligomer. From the available force fields, the optimized potential for liquid simulation (OPLS) force field was used to further investigate which adjustments to the force field would improve the agreement of simulated physical properties with experimental ones. Two parameters were identified and adjusted, the (HO)–C–C–O proper dihedral potential and the polarity of the hydroxy group. The parameter adjustments depended on the size of the ethylene glycol oligomer. Next, PEG200 was simulated with the OPLS force field with and without modifications to inspect their effects on the simulation results. The modifications to the OPLS force field significantly decreased hydrogen bonding overall and increased the propensity of intramolecular hydrogen bond formation at the cost of intermolecular hydrogen bond formation. Moreover, some of the tri- and more so tetraethylene glycol formed intramolecular hydrogen bonds between the hydroxy end groups while still maintaining strong intramolecular interactions with the ether oxygen atoms. These observations allowed the interpretation of the obtained RDFs as well as structural properties such as the average end-to-end distances and the average radii of gyration. The MD simulations with and without the modifications showed no evidence of preferential association of like-oligomers to form clusters nor any evidence of long-range ordering such as a side-by-side stacking of ethylene glycol oligomers. Instead, the simulation results support the picture of PEG200 being a random mixture of its ethylene glycol oligomer components. Finally, additional MD simulations of a binary mixture of tri-and hexaethylene glycol with the same average molar weight as PEG200 revealed very similar structural and physical properties as for PEG200.

中文翻译：

多分散聚乙二醇PEG200中乙二醇组分的行为研究

^{报道了 [聚乙二醇 (PEG)200] 的分子动力学 (MD) 模拟，这是一种平均摩尔重量为 200 g·mol –1}的乙二醇低聚物的多分散混合物. 作为第一步，对描述乙二醇低聚物的可用力场进行了测试，以了解它们再现实验特性的准确性。发现它们在再现密度（一种静态属性）或自扩散系数（一种动态属性）方面都不尽如人意。与实验数据的差异随着测试的乙二醇低聚物尺寸的增加而增加。从可用的力场中，液体模拟 (OPLS) 力场的优化势被用于进一步研究对力场的哪些调整将提高模拟物理特性与实验物理特性的一致性。确定并调整了两个参数，即 (HO)–C–C–O 固有二面角势和羟基的极性。参数调整取决于乙二醇低聚物的大小。接下来，使用 OPLS 力场对 PEG200 进行了模拟，修改和未修改以检查它们对模拟结果的影响。对 OPLS 力场的修改显着降低了整体氢键，并以分子间氢键形成为代价增加了分子内氢键形成的倾向。此外，一些三甘醇和更多的四甘醇在羟基端基之间形成分子内氢键，同时仍保持与醚氧原子的强分子内相互作用。这些观察允许解释获得的 RDF 以及结构特性，例如平均端到端距离和平均回转半径。有和没有修改的 MD 模拟没有显示类似低聚物优先缔合形成簇的证据，也没有任何长程排序的证据，例如乙二醇低聚物的并排堆叠。相反，模拟结果支持 PEG200 是其乙二醇低聚物组分的随机混合物的图片。最后，对具有与 PEG200 相同平均摩尔量的三乙二醇和六乙二醇的二元混合物的额外 MD 模拟揭示了与 PEG200 非常相似的结构和物理性质。模拟结果支持 PEG200 是其乙二醇低聚物组分的随机混合物的图片。最后，对具有与 PEG200 相同平均摩尔量的三乙二醇和六乙二醇的二元混合物的额外 MD 模拟揭示了与 PEG200 非常相似的结构和物理性质。模拟结果支持 PEG200 是其乙二醇低聚物组分的随机混合物的图片。最后，对具有与 PEG200 相同平均摩尔量的三乙二醇和六乙二醇的二元混合物的额外 MD 模拟揭示了与 PEG200 非常相似的结构和物理性质。

更新日期：2023-01-26

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