Bicontinuous Fluid Structure with Low Cohesive Energy: Molecular Basis for Exceptionally Low Interfacial Tension of Complex Coacervate Fluids
Bicontinuous Fluid Structure with Low Cohesive Energy: Molecular Basis for Exceptionally Low Interfacial Tension of Complex Coacervate Fluids
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DOI：
10.1021/acsnano.5b07787
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发表时间：
2016-05-01
期刊：
影响因子：
17.1
通讯作者：
Hwang, Dong Soo
中科院分区：
文献类型：
--
作者：
Huang, Kuo-Ying;Yoo, Hee Young;Hwang, Dong Soo
从称为复合凝聚层的双相流体中分离出来的浓缩的纳米复合物的致密流体的特别低的界面张力代表了一种独特且备受追捧的材料性质，其激发了从上级涂层到湿粘合的新应用。尽管有广泛的研究和广泛的兴趣，复杂凝聚体的独特性质的分子和结构基础尚不清楚。这里，通过以化学计量比混合作为聚阳离子的重组贻贝足蛋白-1（mfp-1）和作为聚阴离子的透明质酸（HA）而产生的微相分离的复合凝聚层流体被宏观地相分离成致密的复合凝聚层和稀释的上清液相，以使得能够分离表征两个流体相。令人惊讶的是，尽管聚电解质的密度相差高达4个数量级，但发现水在这两相中的扩散率是不可区分的。在稠密流体中存在未结合的、大块状的水，这可以与仅被微扰界面和网络微弱扰动的水种群相调和。通过宏观相分离的致密复合凝聚相的低温-TEM实验验证了这一假设，发现该凝聚相是双连续和双相纳米结构网络，其中一个相通过染色技术确认为水和其他的水溶性复合物。我们的结论是，水的水和水的聚电解质之间的弱内聚能表现在一个双连续的网络，并负责这个复杂的流体相的界面能非常低，几乎任何表面内的水性介质。
An exceptionally low interfacial tension of a dense fluid of concentrated polyelectrolyte complexes, phase separated from a biphasic fluid known as complex coacervates, represents a unique and highly sought-after materials property that inspires novel applications from superior coating to wet adhesion. Despite extensive studies and broad interest, the molecular and structural bases for the unique properties of complex coacervates are unclear. Here, a microphase-separated complex coacervate fluid generated by mixing a recombinant mussel foot protein-1 (mfp-1) as the polycation and hyaluronic acid (HA) as the polyanion at stoichiometric ratios was macroscopically phase-separated into a dense complex coacervate and a dilute supernatant phase to enable separate characterization of the two fluid phases. Surprisingly, despite up to 4 orders of magnitude differing density of the polyelectrolytes, the diffusivity of water in these two phases was found to be indistinguishable. The presence of unbound, bulk-like, water in the dense fluid can be reconciled with a water population that is only weakly perturbed by the polyelectrolyte interface and network. This hypothesis was experimentally validated by cryo-TEM of the macroscopically phase-separated dense complex coacervate phase that was found to be a bicontinuous and biphasic nanostructured network, in which one of the phases was confirmed by staining techniques to be water and the other polyelectrolyte complexes. We conclude that a weak cohesive energy between water water and water polyelectrolytes manifests itself in a bicontinuous network, and is responsible for the exceptionally low interfacial energy of this complex fluid phase with respect to virtually any surface within an aqueous medium.