Role of electrostatic correlations in polyelectrolyte charge association
Role of electrostatic correlations in polyelectrolyte charge association
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DOI：
10.1063/1.5034454
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发表时间：
2018-10-28
影响因子：
4.4
通讯作者：
Qin, Jian
中科院分区：
文献类型：
--
作者：
Friedowitz, Sean;Salehi, Ali;Qin, Jian
可逆的离子结合平衡在水溶液中的强烈影响解离的离子物种之间的相互作用。我们研究了聚电解质上离子基团之间的结构相关性如何影响反离子结合。用经典的Debye-Huckel表达式处理静电相关自由能，导致在浓缩状态下完全的反离子解离。这种非物理的行为是源于不适当的正则化的解离离子和聚离子的自能，并减轻涂抹点样电荷在有限的宽度。通过将Debye-Huckel自由能推广到具有可变分维和刚度的聚电解质，阐述了自能对反离子结合的影响。在稀释制度中，更大的倾向结合被发现的链与更紧凑的架构，这反过来又减少了苛刻的自我排斥紧密包装的安排的电荷。在集中的制度，静电相关的影响减弱，由于屏蔽和结合的程度是由短程相互作用和离子的平移熵的平衡。出版社：AIP Publishing
Reversible ion binding equilibria in polyelectrolyte solutions are strongly affected by interactions between dissociated ionic species. We examine how the structural correlations between ionic groups on polyelectrolytes impact the counterion binding. Treating the electrostatic correlation free energy using the classical Debye-Huckel expression leads to complete counterion dissociation in the concentrated regime. This unphysical behavior is shown to stem from improper regularization of the self-energy of dissociated ions and polyions and is mitigated by smearing point-like charges across a finite width. The influence of the self-energy on counterion binding is elaborated on by generalizing the Debye-Huckel free energy to polyelectrolytes with variable fractal dimension and stiffness. In the dilute regime, a greater propensity for binding is found for chains with more compact architectures, which in turn reduces the harsh self-repulsions of tightly packed arrangements of charge. In the concentrated regime, the effects of electrostatic correlations weaken due to screening and the extent of binding is governed by a balance of short-ranged interactions and the translational entropy of ions. Published by AIP Publishing.