Hydrophilic Macroionic Solutions - the Roles of Counterions, Co-ions and Surface Water Layers

在这个由化学系高分子、超分子和纳米化学项目资助的项目中，阿克伦大学的刘天波教授探索了大分子离子的溶液性质。这些大离子的大小在1到10纳米之间，是简单离子和大胶体之间缺失的一环。该项目旨在探索宏离子的微观特征及其与当地环境的相互作用，即反离子、共离子以及它们在水中形成的层状结构。人们正在探索这些相互作用，以揭示宏离子独特的溶液性质背后的根本原因，例如它们自组装成类似黑莓的结构。黑莓的形成过程被发现与病毒衣壳的形成过程相似。这项研究可能会对其他领域产生广泛影响，如物理化学、超分子化学、生物化学、材料科学和纳米技术。该项目包括培养研究生和本科生，并鼓励高中生参加国家科学竞赛和科学事业。研究基础设施正在通过科学合作得到加强。这项研究有三个相辅相成的部分。首先，大离子-反离子相互作用的特征是确定大离子周围反离子的径向分布，以及在存在过多反离子时大离子的稳定性。其次，考察了共离子对大离子的影响，特别是手性大离子与手性共离子之间的优先相互作用。第三，研究了反离子和大离子相互作用过程中地表水结构的详细变化。研究中使用了相对简单的模型，主要是多金属氧酸盐簇合物和金属-有机纳米笼。溶液研究采用了多种技术，如静态和动态激光光散射、同步加速器小角X射线散射、等温滴定、核磁共振、电子显微镜和Zeta电位分析。这些结论可望具有普遍意义，并可能对理解更复杂的体系，如聚电解质和生物大分子溶液具有指导意义。

In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Professor Tianbo Liu of the University of Akron explores the solution properties of macroions. These macroions are between 1 and 10 nanometers (nm) in size and represent a missing link between simple ions and large colloids. The project aims to explore the microscopic features of macroions and their interactions with local environments, that is, the counterions, the co-ions, and the layered structures they make in water. These interactions are being explored in order to unveil the fundamental reasons behind the unique solution properties of the macroions such as their self-assembly into blackberry-like structures. The blackberry formation process is found to mimic the virus capsid formation process. This research could have broad impacts on other fields, such as physical chemistry, supramolecular chemistry, biochemistry, materials sciences and nanotechnology. The project involves training graduate and undergraduate students, and encouraging high school students to participate in national science competitions and scientific careers. The research infrastructure is being enhanced through scientific collaborations.The research has three complementary components. First, the macroion-counterion interaction is being characterized by determining the radial distributions of counterions around macroions and the stability of the macroions in the presence of an excess number of counterions. Secondly, the effect of co-ions on the macroions are being examined, particularly for the preferential interactions between chiral macroions and chiral co-ions. Third, the detailed changes of surface water structures of both counterions and macroions during their interaction are being studied. Relatively simple models, mainly polyoxometalate clusters and metal-organic nanocages, are employed for the study. The solution studies employ a combination of techniques, such as static and dynamic laser light scattering, synchrotron small-angle X-ray scattering, isothermal titration, nuclear magnetic resonance, electron microscopy, and Zeta potential analysis. The conclusions are expected to be universal and may be instructive for understanding more complex systems such as polyelectrolyte and biomacromolecular solutions.