Rumyantsev Artem M, Borisov Oleg V, de Pablo Juan J
Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States.
Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux, UMR 5254 CNRS UPPA, Pau 64053, France.
Macromolecules. 2023 Feb 14;56(4):1713-1730. doi: 10.1021/acs.macromol.2c02464. eCollection 2023 Feb 28.
We develop a scaling theory for the structure and dynamics of "hybrid" complex coacervates formed from linear polyelectrolytes (PEs) and oppositely charged spherical colloids, such as globular proteins, solid nanoparticles, or spherical micelles of ionic surfactants. At low concentrations, in stoichiometric solutions, PEs adsorb at the colloids to form electrically neutral finite-size complexes. These clusters attract each other through bridging between the adsorbed PE layers. Above a threshold concentration, macroscopic phase separation sets in. The coacervate internal structure is defined by (i) the adsorption strength and (ii) the ratio of the resulting shell thickness to the colloid radius, /. A scaling diagram of different coacervate regimes is constructed in terms of the colloid charge and its radius for Θ and athermal solvents. For high charges of the colloids, the shell is thick, ≫ , and most of the volume of the coacervate is occupied by PEs, which determine its osmotic and rheological properties. The average density of hybrid coacervates exceeds that of their PE-PE counterparts and increases with nanoparticle charge, . At the same time, their osmotic moduli remain equal, and the surface tension of hybrid coacervates is lower, which is a consequence of the shell's inhomogeneous density decreasing with the distance from the colloid surface. When charge correlations are weak, hybrid coacervates remain liquid and follow Rouse/reptation dynamics with a -dependent viscosity, η ∼ and η ∼ for a Θ solvent. For an athermal solvent, these exponents are equal to 0.89 and 2.68, respectively. The diffusion coefficients of colloids are predicted to be strongly decreasing functions of their radius and charge. Our results on how affects the threshold coacervation concentration and colloidal dynamics in condensed phases are consistent with experimental observations for and studies of coacervation between supercationic green fluorescent proteins (GFPs) and RNA.
我们针对由线性聚电解质（PEs）与带相反电荷的球形胶体（如球状蛋白质、固体纳米颗粒或离子型表面活性剂的球形胶束）形成的“混合”复合凝聚层的结构和动力学，开发了一种标度理论。在低浓度的化学计量溶液中，PEs吸附在胶体上形成电中性的有限尺寸复合物。这些聚集体通过吸附的PE层之间的桥连相互吸引。超过阈值浓度时，宏观相分离开始。凝聚层的内部结构由（i）吸附强度和（ii）所得壳层厚度与胶体半径的比值/定义。针对θ溶剂和无热溶剂，根据胶体电荷及其半径构建了不同凝聚层状态的标度图。对于高电荷胶体，壳层较厚，≫，凝聚层的大部分体积由PEs占据，这决定了其渗透和流变性质。混合凝聚层的平均密度超过其PE-PE对应物的平均密度，并随纳米颗粒电荷增加。同时，它们的渗透模量保持相等，且混合凝聚层的表面张力较低，这是壳层密度随距胶体表面距离不均匀降低的结果。当电荷相关性较弱时，混合凝聚层保持液态，并遵循具有与相关的粘度的Rouse/爬行动力学，对于θ溶剂，η ∼ 且η ∼ 。对于无热溶剂，这些指数分别等于0.89和2.68。预计胶体的扩散系数是其半径和电荷的强烈递减函数。我们关于如何影响凝聚相中的阈值凝聚浓度和胶体动力学的结果，与超阳离子绿色荧光蛋白（GFPs）和RNA之间凝聚的和研究的实验观察结果一致。
