Ultrastructure of Critical-Gel-like Polyzwitterion–Polyoxometalate Complex Coacervates: Effects of Temperature, Salt Concentration, and Shear
Ultrastructure of Critical-Gel-like Polyzwitterion–Polyoxometalate Complex Coacervates: Effects of Temperature, Salt Concentration, and Shear
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临界凝胶状聚两性离子-多金属氧酸盐复合凝聚层的超微结构：温度、盐浓度和剪切力的影响
DOI：
10.1021/acs.macromol.0c01618
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发表时间：
2020
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;Lin, Kehua;Li, Ruipeng;Yavitt, Benjamin M.;Qiu, Jie;Fukuto, Masafumi;Zhu, Yingxi
非常规复合凝聚体的结构，如聚合物-非聚合物复合凝聚体，与具有对称电荷物种的相反电荷聚电解质之间形成的常规凝聚体相比，研究得较少。然而，它们的微观结构组织对于进一步阐明络合时液-液相分离过程的机理是重要的。在这项工作中，我们用原位温度和剪切控制的小角X射线散射(SAXS)表征了无机多金属氧酸盐(POM)和多两性离子之间形成的复合凝聚体的微观结构。尽管光学显微镜观察到致密凝聚体具有明显的透明和均匀的形貌，但我们之前的结果(大分子2018，51，22,9405POM9411)表明，致密的聚两性离子-−凝聚体表现出临界凝胶状网络，包括贫络合区(网孔)和富络合区(连接网络)。本工作中报道的SAXS结果支持富络合物区域实际上是由多两性离子连接的松散排列的POM聚集体的形式，被称为络合物粒子。由于POMS与凝聚体中其他组分具有较高的X射线散射对比度，针对不同的组成和盐浓度、温度和剪切，进一步检查了聚集复杂颗粒的结构。随着POM/聚两性离子浓度比的增加，稠密凝聚体中的复杂颗粒似乎随着POM聚集体的紧密堆积而增长，而随着盐浓度的降低，POM聚集体的松散堆积呈现出相反的趋势。相反，提高温度可以得到更小的复杂颗粒，其中包含更松散的POM聚集体，这与致密凝聚体的温度相关粘弹性一致。此外，这种基于POM的混合致密凝聚体表现出有趣的应变硬化行为，这是由于复杂颗粒内的剪切增强POM堆积造成的。与大多数传统的交联型聚合物网络的剪切变稀行为不同，聚两性离子-聚甲醛共聚体的应变硬化特性与热和盐响应特性相结合，可以拓宽有机-无机大离子共聚体作为在极端环境条件下工作的智能功能材料的应用。
The structure of unconventional complex coacervates, such as polymer–nonpolymer complex coacervates, remains less investigated than that of the conventional coacervates formed between oppositely charged polyelectrolytes with symmetric charge species. Yet, their microscopic structural organization is important to further elucidate the mechanism of liquid–liquid-phase separation processes upon complexation. In this work, we characterize the microstructural organization of complex coacervates formed between inorganic polyoxometalate (POM) and polyzwitterion by small-angle X-ray scattering (SAXS) with in situ temperature and shear control. Despite the apparent transparent and homogeneous morphology of dense coacervates as observed by optical microscopy, our previous results (Macromolecules2018, 51, 22, 9405−9411) suggest that dense polyzwitterion–POM coacervates exhibit critical-gel-like networks containing both complex-poor region (mesh pore) and complex-rich region (connective network). SAXS results as reported in this work support that the complex-rich region is actually in the form of loosely packed POM aggregates linked by polyzwitterion, designated as complex particles. The structure of aggregating complex particles is further examined against varied composition and salt concentrations, temperature, and shear, thanks to the high X-ray scattering contrast of POMs from that of other components in the coacervates. The complex particles in the dense coacervates appear to grow with more tightly packed POM aggregates with increasing POM-to-polyzwitterion concentration ratio, in contrast to more loosely packed POM aggregates with decreasing salt concentration. Conversely, increasing temperature could result in smaller complex particles containing more loosely packed POM aggregates, consistent with temperature-dependent viscoelasticity of dense coacervates. Furthermore, such POM-based hybrid dense coacervates exhibit intriguing strain-hardening behavior, resulting from shear-enhanced POM packing inside the complex particles. Distinct from the shear-thinning behavior of most conventional cross-linked polymeric networks, the strain-hardening property combined with thermal- and salt-responsive characteristics of polyzwitterion–POM coacervates could broaden the applications of hybrid organic–inorganic macroion coacervates as smart functional materials working under extreme environmental conditions.
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关键凝胶
DOI：
--
发表时间：
2002
期刊：
影响因子：
--
作者：
H. Winter
通讯作者：
H. Winter
影响因子：
5.5
作者：
Jing, Benxin;Xu, Donghua;Zhu, Yingxi
通讯作者：
Zhu, Yingxi
影响因子：
5.5
作者：
Jing, Benxin;Ferreira, Manuela;Zhu, Yingxi
通讯作者：
Zhu, Yingxi
影响因子：
15.6
作者：
Stewart RJ;Wang CS;Song IT;Jones JP
通讯作者：
Jones JP
影响因子：
17.1
作者：
Huang, Kuo-Ying;Yoo, Hee Young;Hwang, Dong Soo
通讯作者：
Hwang, Dong Soo