Unconventional Complex Coacervation between Neutral Polymer and Inorganic Polyoxometalate in Aqueous Solution via Direct Water Mediation
Unconventional Complex Coacervation between Neutral Polymer and Inorganic Polyoxometalate in Aqueous Solution via Direct Water Mediation
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DOI：
10.1021/acs.macromol.9b01091
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发表时间：
2019-11-12
期刊：
影响因子：
5.5
通讯作者：
Zhu, Yingxi
中科院分区：
文献类型：
--
作者：
Jing, Benxin;Ferreira, Manuela;Zhu, Yingxi
水，特别是水化壳层中的水，对于自然界中的许多生物超分子聚集体是至关重要的，其中水可以通过氢键直接介导分子间缔合，并且被认为是“结构化水”。相反，很少有报道的仿生水介导的超分子组装具有足够高的水含量，到目前为止，因为水的水合和水作为一个积木参与自组装的竞争热力学过程。在这项工作中，我们探索水介导的络合基于熵驱动的两相凝聚形成使用高度亲水性的中性聚合物和无机矿物类似的纳米团簇。对于第一次（据我们所知），非静电液-液分离凝聚层的形成证明聚乙二醇（PEG）和聚氧乙烯（POM）纳米团簇在不同的PEG和POM浓度的水溶液中，POM类型，和水介质条件。使用荧光显微镜、小角X射线散射、量热法和其他技术的综合表征已经证实PEG-POM复合凝聚的组成、微观结构和热力学与水溶液中带相反电荷的聚电解质之间的熵驱动的复合凝聚高度相似。然而，重水对临界POM浓度的凝聚形成的开始的影响表明，水，而不是反离子，通常争论的聚乙二醇复合凝聚，是负责PEG-POM凝聚形成。具体而言，结构化水作为高度水合的PEG和POM两者的氢键供体以直接介导PEG-水-POM缔合，导致释放过量的水合水用于熵驱动的PEG-POM复合凝聚。因此，水介导的复合凝聚可以作为一种通用和简单的策略，以建立仿生杂化纳米材料的高含水量的各种应用，从能源相关的功能纳米材料，生物医学衍生物。
Water, specifically in a hydration shell, is critical for many biological supramolecular aggregations in nature, where water can directly mediate intermolecular association via hydrogen bonding and is regarded as "structured water". Conversely, little has been reported on the biomimetic water-mediated supramolecular assembly with adequately high water content to date, because of the competing thermodynamic processes of water hydration and water as a building block to participate in self-assembly. In this work, we explore water-mediated complexation based on entropy-driven biphasic coacervate formation using highly hydrophilic neutral polymer and inorganic mineral-analogous nanoclusters. For the first time (to the best of our knowledge), nonelectrostatic liquid-liquid separating coacervate formation is demonstrated between polyethylene glycol (PEG) and polyoxometalate (POM) nanoclusters in aqueous solutions of varied PEG and POM concentrations, POM types, and aqueous medium conditions. Comprehensive characterization using fluorescence microscopy, small-angle X-ray scattering, calorimetry, and other techniques has confirmed that the compositions, microstructure, and thermodynamics of PEG-POM complex coacervation are highly similar to entropy-driven complex coacervation between oppositely charged polyelectrolytes in aqueous solution. However, the effect of heavy water on critical POM concentration for the onset of coacervate formation suggests that water, instead of the counter ions as commonly debated for polyelectrolyte complex coacervation, is responsible for PEG-POM coacervate formation. Specifically, structured water works as a hydrogen bond donor for both highly hydrated PEG and POM to directly mediate the PEG-water-POM association, resulting in the release of excess hydrated water for entropy-driven PEG-POM complex coacervation. Therefore, water-mediated complex coacervation could be developed as a general and simple strategy to build biomimetic hybrid nanomaterials with high water content for various applications from energy-related functional nanomaterials to biomedical ramification.