EAGER: Control of Ion Complexation of Neutral Polymers with Inorganic Macroions to Enhance Polymer Mechanical and Ion-Transport Properties

非技术摘要：带电的亚分子基团(离子)与聚合物的结合通常与带电的聚合物在水溶液中由于强烈的静电相互作用而产生离子-聚合物络合物。在某些情况下，离子还可以与非水基介质中的未带电聚合物结合，从而极大地改变聚合物的结构和材料性能。例如，聚氧乙烷(PEO)是一种具有广泛商业应用的不带电荷的水溶性聚合物，它可以将氯化锂等盐溶解在非水溶剂中，生成具有高离子导电性的PEO-离子络合物，作为锂离子充电电池的固体聚合物电解质。尽管离子与中性聚合物结合具有巨大的技术意义，但中性聚合物在有机溶剂和固体中的带电机制仍然知之甚少。本项目旨在通过超快激光光谱方法控制和定量PEO聚合物与不同电荷和浓度的无机纳米离子(宏离子)的电荷密度和络合物的形成。有了这一知识，具有增强的机械和离子传输性能的含离子聚合物(包括在各种溶剂和固态中的富含地球的或常规的合成聚合物)可以被开发成可能与能源和环境相关的新型功能材料。该项目还结合了多方面的STEM教育，将开发课堂和视频演示以及实践经验，以吸引研究生、本科生和高中生参与基础材料设计和先进的材料表征工具。该项目的更广泛影响还将包括招收、留住和辅导STEM领域中任职人数不足的学生，包括女学生。在水溶液中，由于强烈的静电相互作用，离子与带电聚合物或聚电解质之间通常形成聚合物-聚合物络合物。然而，电荷也可以引入中性聚合物，如聚氧乙烷(PEO)，在离子结合时，在非水溶剂和固态，导致不寻常的聚电解质行为的中性聚合物。这是一个研究较少的领域，本项目旨在阐明多价大离子有效充电中性聚合物的过程，从而形成具有增强的类固体机械强度和快速离子传输的聚合物-大离子络合物。特别是，PEO聚合物与不同多价和不同浓度的亲水性无机大离子结合时的电势和络合物的形成将通过超快激光光谱来定量，以从根本上了解中性聚合物在有机溶剂和固体中的电荷过程。建立和开发PEO-大离子络合物的相结构、粘弹性和离子导电性之间的关系，以提高具有最佳大离子含量的络合物的机械强度和离子传输。该项目的成功可能意味着将地球上丰富的或传统的合成中性聚合物转化为具有增强的离子传输和机械完整性的先进功能含离子聚合物的通用和可持续的材料工艺。

NON-TECHNICAL SUMMARY:Binding of electrically charged submolecular groups (ions) to polymers commonly occurs with charged polymers in water solution to produce ion-polymer complexes due to strong electrostatic interactions. In some cases ions can also bind with uncharged polymers in non-water-based media to greatly modify the structure and material properties of the polymers. For instance, poly(ethylene oxide) (PEO), an uncharged water-soluble polymer with extensive commercial applications, can dissolve salts, such as lithium chloride, in non-aqueous solvents to produce PEO-ion complex with high ion conductivity as solid polymer electrolyte for Li-ion rechargeable battery applications. Despite enormous technical implications of ion binding with neutral polymers the charging mechanism of neutral polymers in organic solvents and in the solid state remains poorly understood. This project aims to control and quantify the electrical charge density and complex formation of PEO polymers with inorganic nanometer-sized ions (macroions) of varied electrical charges and concentration by ultrafast laser spectroscopic methods. With this knowledge, ion-containing polymers with enhanced mechanical and ion transport properties can be developed (including earth-abundant or conventional synthetic polymers in various solvents and in the solid state) into novel functional materials that may be relevant for energy and environmental aspects. This project also combines multifaceted STEM education, where classroom and video demonstrations and hand-on experiences will be developed to engage graduate, undergraduate, and high-school students in fundamental materials design and advanced materials-characterization tools. Broader impacts of this project will also include the recruitment, retention, and mentoring of underrepresented students, including women students, in the STEM fields. TECHNICAL SUMMARYIon-polymer complexes are commonly formed between ions and charged polymers or polyelectrolytes in aqueous solution due to strong electrostatic interaction. However, electrical charges can be also introduced to neutral polymers, such as poly(ethylene oxide) (PEO), upon ion binding in non-aqueous solvents and in the solid state, resulting in unusual polyelectrolyte-like behaviors of the neutral polymers. This is a much less studied area, and this project aims to elucidate the process of effectively charging neutral polymers by multivalent macroions, leading to the formation of polymer-macroion complexes with enhanced solid-like mechanical strength and fast ion transport. In particular, the electric potential and complex formation of PEO polymers upon binding with hydrophilic inorganic macroions of varied multi-valence and concentration will be quantified by ultrafast laser spectroscopy to fundamentally understand the electrical charging process of neutral polymers in organic solvents and the solid state. The relationship among phase structure, viscoelasticity, and ion conductivity of PEO-macroion complexes will be established and exploited to enhance the mechanical strength and ion transport of the complexes with optimal macroion content. The success of this project could have implications toward a versatile and sustainable material process of earth-abundant or conventional synthetic neutral polymers into advanced functional ion-containing polymers with enhanced ion transport and mechanical integrity.