不同溶剂质量的聚合物溶液中的链构象和相分离,Journal of Polymer Science

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不同溶剂质量的聚合物溶液中的链构象和相分离
Journal of Polymer Science ( IF 3.9 ) Pub Date : 2021-10-02 , DOI: 10.1002/pol.20210526
Yisheng Huang ₁ , Shengfeng Cheng _{1,

2}

Affiliation

当聚合物和溶剂之间的相互作用强度发生变化时，分子动力学模拟用于研究由 Kremer-Grest 珠弹簧模型表示的单个聚合物链的构象，在以 Lennard-Jones 液体作为溶剂的溶液中。结果表明，当聚合物-溶剂相互作用不利时，链会像在不良溶剂中预期的那样坍塌。对于更具吸引力的聚合物-溶剂相互作用，溶剂质量提高，链越来越多地溶剂化，并表现出理想的然后膨胀的构象。然而，随着聚合物-溶剂相互作用强度进一步增加至聚合物-聚合物和溶剂-溶剂相互作用强度的约两倍以上，该链表现出意想不到的塌陷行为。相应地，对于强聚合物溶剂吸引力，在多链的溶液中观察到相分离。这些结果表明，在非常有吸引力的聚合物-溶剂相互作用下，溶剂再次变得有效贫乏。尽管如此，在此限制下链塌陷和相分离的机制与由于不利的聚合物 - 溶剂相互作用而导致不良溶剂的情况不同。在后者中，溶剂被排除在坍缩链的域之外，而在前者中，溶剂仍然存在于坍缩链的渗透体积中或与纯溶剂相分离的富含聚合物的域中。在强聚合物溶剂吸引力的限制下，溶剂表现为将单体粘在一起的胶水，导致单链坍塌和多链聚合和相分离。在多链的溶液中观察到相分离。这些结果表明，在非常有吸引力的聚合物-溶剂相互作用下，溶剂再次变得有效贫乏。尽管如此，在此限制下链塌陷和相分离的机制与由于不利的聚合物 - 溶剂相互作用而导致不良溶剂的情况不同。在后者中，溶剂被排除在坍缩链的域之外，而在前者中，溶剂仍然存在于坍缩链的渗透体积中或与纯溶剂相分离的富含聚合物的域中。在强聚合物溶剂吸引力的限制下，溶剂表现为将单体粘在一起的胶水，导致单链坍塌和多链聚合和相分离。在多链的溶液中观察到相分离。这些结果表明，在非常有吸引力的聚合物-溶剂相互作用下，溶剂再次变得有效贫乏。尽管如此，在此限制下链塌陷和相分离的机制与由于不利的聚合物 - 溶剂相互作用而导致不良溶剂的情况不同。在后者中，溶剂被排除在坍缩链的域之外，而在前者中，溶剂仍然存在于坍缩链的渗透体积中或与纯溶剂相分离的富含聚合物的域中。在强聚合物溶剂吸引力的限制下，溶剂表现为将单体粘在一起的胶水，导致单链坍塌和多链聚合和相分离。

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Chain conformations and phase separation in polymer solutions with varying solvent quality

Molecular dynamics simulations are used to investigate the conformations of a single polymer chain, represented by the Kremer-Grest bead-spring model, in a solution with a Lennard-Jones liquid as the solvent when the interaction strength between the polymer and solvent is varied. Results show that when the polymer-solvent interaction is unfavorable, the chain collapses as one would expect in a poor solvent. For more attractive polymer-solvent interactions, the solvent quality improves and the chain is increasingly solvated and exhibits ideal and then swollen conformations. However, as the polymer-solvent interaction strength is increased further to be more than about twice the strength of the polymer-polymer and solvent-solvent interactions, the chain exhibits an unexpected collapsing behavior. Correspondingly, for strong polymer-solvent attractions, phase separation is observed in the solutions of multiple chains. These results indicate that the solvent becomes effectively poor again at very attractive polymer-solvent interactions. Nonetheless, the mechanism of chain collapsing and phase separation in this limit differs from the case with a poor solvent rendered by unfavorable polymer-solvent interactions. In the latter, the solvent is excluded from the domain of the collapsed chains while in the former, the solvent is still present in the pervaded volume of a collapsed chain or in the polymer-rich domain that phase separates from the pure solvent. In the limit of strong polymer-solvent attractions, the solvent behaves as a glue to stick monomers together, causing a single chain to collapse and multiple chains to aggregate and phase separate.

更新日期：2021-11-15

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