Peng B, Muthukumar M
Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
J Chem Phys. 2015 Dec 28;143(24):243133. doi: 10.1063/1.4936256.
We have simulated the invasion of a polyelectrolyte complex made of a polycation chain and a polyanion chain, by another longer polyanion chain, using the coarse-grained united atom model for the chains and the Langevin dynamics methodology. Our simulations reveal many intricate details of the substitution reaction in terms of conformational changes of the chains and competition between the invading chain and the chain being displaced for the common complementary chain. We show that the invading chain is required to be sufficiently longer than the chain being displaced for effecting the substitution. Yet, having the invading chain to be longer than a certain threshold value does not reduce the substitution time much further. While most of the simulations were carried out in salt-free conditions, we show that presence of salt facilitates the substitution reaction and reduces the substitution time. Analysis of our data shows that the dominant driving force for the substitution process involving polyelectrolytes lies in the release of counterions during the substitution.
我们使用链的粗粒化联合原子模型和朗之万动力学方法，模拟了由聚阳离子链和聚阴离子链组成的聚电解质复合物被另一条更长的聚阴离子链侵入的过程。我们的模拟揭示了取代反应在链的构象变化以及侵入链与被取代链争夺共同互补链方面的许多复杂细节。我们表明，侵入链需要比被取代链长得足够多才能实现取代。然而，使侵入链长于某个阈值并不会进一步大幅减少取代时间。虽然大多数模拟是在无盐条件下进行的，但我们表明盐的存在促进了取代反应并缩短了取代时间。对我们数据的分析表明，涉及聚电解质的取代过程的主要驱动力在于取代过程中抗衡离子的释放。
