Department of Chemistry, University of Illinois at Urbana-Champaign, 505 S. Mathews, Urbana, Illinois 61801, USA.
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 S. Mathews, Urbana, Illinois 61801, USA.
J Chem Phys. 2018 Oct 28;149(16):163315. doi: 10.1063/1.5029934.
Polymeric occurs when two oppositely charged polyelectrolytes undergo an associative phase separation in aqueous salt solution, resulting in a polymer-dense phase and a polymer-dilute phase. This phase separation process represents a powerful way to tune polymer solutions using electrostatic attraction and is sensitive to environmental conditions such as salt concentration and valency. One area of particular research interest is using this to create nanoscale polymer assemblies, via (for example) block copolymers with coacervate-forming blocks. The key to understanding coacervate-driven assembly is the formation of the interface between the coacervate and supernatant phases and its corresponding thermodynamics. In this work, we use recent advances in coacervate simulation and theory to probe the nature of the coacervate-supernatant interface. First, we show that self-consistent field theory informed by either Monte-Carlo simulations transfer matrix theories is capable of reproducing interfacial features present in large-scale molecular dynamics simulations. The quantitative agreement between all three methods gives us a way to efficiently explore interfacial thermodynamics. We show how salt affects the interface, and we find qualitative agreement with literature measurements of interfacial tension. We also explore the influence of neutral polymers, which we predict to drastically influence the phase behavior of coacervates. These neutral polymers can significantly alter the interfacial tension in coacervates; this has a profound effect on the design and understanding of coacervate-driven self-assembly, where the equilibrium structure is tied to interfacial properties.
聚合物在带相反电荷的聚电解质在盐溶液中发生缔合相分离时发生，导致聚合物致密相和聚合物稀释相。这种相分离过程代表了一种使用静电吸引来调节聚合物溶液的有效方法，并且对环境条件（例如盐浓度和价态）敏感。一个特别受关注的研究领域是利用这一点通过（例如）具有共凝聚形成块的嵌段共聚物来创建纳米级聚合物组装体。理解共凝聚驱动组装的关键是共凝聚物和上清液相之间界面的形成及其相应的热力学。在这项工作中，我们使用共凝聚模拟和理论的最新进展来探测共凝聚物-上清液界面的性质。首先，我们表明由蒙特卡罗模拟或转移矩阵理论提供信息的自洽场理论能够重现大规模分子动力学模拟中存在的界面特征。这三种方法之间的定量一致性为我们提供了一种有效探索界面热力学的方法。我们展示了盐如何影响界面，并且我们发现与文献中界面张力的测量结果定性一致。我们还探索了中性聚合物的影响，我们预测中性聚合物会极大地影响共凝聚物的相行为。这些中性聚合物可以显着改变共凝聚物中的界面张力；这对共凝聚物驱动的自组装的设计和理解有深远的影响，其中平衡结构与界面性质有关。
