Closed-Loop Phase Behavior of Nonstoichiometric Coacervates in Coarse-Grained Simulations
Closed-Loop Phase Behavior of Nonstoichiometric Coacervates in Coarse-Grained Simulations
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DOI：
10.1021/acs.macromol.1c02115
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发表时间：
2022-01-10
期刊：
影响因子：
5.5
通讯作者：
Milner, Scott T.
中科院分区：
文献类型：
--
作者：
Bobbili, Sai Vineeth;Milner, Scott T.
大多数关于双凝聚层相行为的研究都集中在带相反电荷的聚合物的对称混合物上。在这里，我们使用一个粗粒度的模拟，其中所有的键合单体和移动的抗衡离子表示为Lennard-Jones粒子与单位电荷和直径等于Bjerrum长度，研究电荷不对称的凝聚相行为的影响。我们研究了盐对各相中聚合物和移动的离子浓度的影响，并定性地再现了在最近的非化学计量凝聚层实验中观察到的闭环行为。我们发现，从添加盐的抗衡离子分布不均匀，更喜欢稀相，以最大限度地提高其平移熵，类似于唐南平衡的带电膜。凝聚相在渗透压下收缩，导致少量添加盐的聚合物浓度增加。
Most studies of polyelectrolyte coacervate phase behavior focus on symmetric mixtures of oppositely charged polymers. Here we use a coarse-grained simulation, in which all bonded monomers and mobile counterions are represented as Lennard-Jones particles with unit charge and diameter equal to the Bjerrum length, to study the impact of charge asymmetry on coacervate phase behavior. We study the impact of salt on the concentration of polymers and mobile ions in each phase and qualitatively reproduce the closed-loop behavior observed in recent experiments on nonstoichiometric coacervates. We find that the counterions from added salt distribute unevenly, preferring the dilute phase to maximize their translational entropy, analogous to Donnan equilibrium for a charged membrane. The coacervate phase shrinks under osmotic pressure, leading to increased polymer concentration with small amounts of added salt.