Jiang Jiadi, Chen Er-Qiang, Yang Shuang
Beijing National Laboratory for Molecular Sciences, Department of Polymer Science and Engineering and Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, People's Republic of China.
J Chem Phys. 2021 Apr 14;154(14):144903. doi: 10.1063/5.0044845.
The incorporation of oppositely charged polyelectrolytes into a block copolymer system can lead to formation of microphase separated nanostructures driven by the electrostatic complex between two oppositely charged blocks. It is a theoretical challenge to build an appropriate model to handle such coacervate-driven self-assembly, which should capture the strong electrostatic correlations for highly charged polymers. In this paper, we develop the self-consistent field theory considering the ion paring effect to predict the phase behavior of block polyelectrolytes. In our model, two types of ion pairs, the binding between two oppositely charged monomers and the binding between charged monomers and counterions, are included. Their strength of formation is controlled by two parameters K and K, respectively. We give a detailed analysis about how the binding strength K and K and salt concentration affect the self-assembled nanostructure of diblock polyelectrolyte systems. The results show that the binding between two oppositely charged blocks provides driven force for microphase separation, while the binding between charged monomers and counterions competes with the polyion pairing and thus suppresses the microphase separation. The addition of salt has a shielding effect on the charges of polymers, which is a disadvantage to microphase separation. The phase diagrams as a function of polymer concentration and salt concentration at different situations are constructed, and the influence of K, K, and charged block composition f is analyzed in depth. The obtained phase diagrams are in good agreement with currently existing experimental and theoretical results.
将带相反电荷的聚电解质掺入嵌段共聚物体系中，可导致由两个带相反电荷的嵌段之间的静电复合物驱动形成微相分离的纳米结构。构建一个合适的模型来处理这种凝聚驱动的自组装是一项理论挑战，该模型应捕捉高电荷聚合物的强静电相关性。在本文中，我们发展了考虑离子配对效应的自洽场理论，以预测嵌段聚电解质的相行为。在我们的模型中，包括两种类型的离子对，即两个带相反电荷的单体之间的结合以及带电单体与抗衡离子之间的结合。它们的形成强度分别由两个参数K和K控制。我们详细分析了结合强度K和K以及盐浓度如何影响双嵌段聚电解质体系的自组装纳米结构。结果表明，两个带相反电荷的嵌段之间的结合为微相分离提供驱动力，而带电单体与抗衡离子之间的结合与聚离子配对竞争，从而抑制微相分离。盐的加入对聚合物的电荷有屏蔽作用，这对微相分离不利。构建了不同情况下作为聚合物浓度和盐浓度函数的相图，并深入分析了K、K和带电嵌段组成f的影响。所得相图与目前现有的实验和理论结果吻合良好。
