Ion Content of Polyelectrolyte Complex Coacervates and the Donnan Equilibrium
Ion Content of Polyelectrolyte Complex Coacervates and the Donnan Equilibrium
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DOI：
10.1021/acs.macromol.9b01755
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发表时间：
2019-12-10
期刊：
影响因子：
5.5
通讯作者：
Wang, Qifeng
中科院分区：
文献类型：
--
作者：
Schlenoff, Joseph B.;Yang, Mo;Wang, Qifeng
不透明带电的聚电解质在溶液中自发地结合成水合复合物或凝聚物，佩奇。佩奇的形态、稳定性和性质强烈地取决于它们的离子含量，其调节Pol（+）和Pol（-）带相反电荷的重复单元之间的“粘性”可逆相互作用。在这里，它示出的PEC和水溶液中，它被浸泡的离子之间的分布是准确预测的唐南平衡。对于理想的聚电解质的化学计量混合，对应于络合焓Δ H-PEC -> 0，PEC内的盐MA浓度[MA]（PEC）等于溶液盐浓度[MA]（s）。沿着Hofmeister级数的等温量热测量表明，如果混合是放热的，[MA]（PEC）< [MA]（s），而对于Pol（+）和Pol（-）的吸热缔合，[MA]（PEC）> [MA]（s）。一组简单的自洽表达式说明PEC盐响应，而不考虑带电物种之间的净库仑力或静电力。Δ H-PEC精确地预测了与理想的道南平衡的偏差，道南平衡与Pol（+）Pol（-）和非本征Pol（+）A（-）和Pol（-）M（+）对的相关或本征对之间的平衡有关，其中抗衡离子补偿了负电荷。Pol（+）Pol（-）对形成的平衡常数K-对显示为与水合的无离子络合物的体积电荷密度成比例。K对也可用于估计聚电解质完全解离的临界盐浓度。
Oppositely charged polyelectrolytes in solution spontaneously associate into hydrated complexes or coacervates, PECs. The morphology, stability, and properties of PECs depend strongly on their ion content, which moderates the "sticky" reversible interactions between Pol(+) and Pol(-) oppositely charged repeat units. Here, it is shown that the distribution of ions between a PEC and the aqueous solution in which it is immersed is accurately predicted by the Donnan equilibrium. For ideal, stoichiometric mixing of polyelectrolytes, corresponding to an enthalpy of complexation Delta H-PEC -> 0, the salt, MA, concentration inside the PEC, [MA](PEC), is equal to the solution salt concentration, [MA](s). Isothermal calorimetry measurements along a Hofmeister series show that if mixing is exothermic, [MA](PEC) < [MA](s), while for endothermic association of Pol(+) and Pol(-), [MA](PEC) > [MA](s). A set of simple self-consistent expressions illustrate PEC salt response without consideration of net Coulombic or electrostatic forces between charged species. Delta H-PEC exactly predicts deviations from ideal Donnan equilibria, which are connected to the equilibria between associated or intrinsic pairs of Pol(+)Pol(-) and extrinsic Pol(+)A(-) and Pol(-)M(+) pairs, where counterions compensate polyelectrolyte charges. The equilibrium constant K-pair for Pol(+)Pol(-) pair formation is shown to be proportional to the volume charge density of the hydrated, ion-free complex. K-pair may also be used to estimate the critical salt concentration at which polyelectrolytes completely dissociate.