Cooperative Transport in Ion-Conducting Membranes

含离子聚合物膜是许多技术的关键组成部分，包括化学分离、水净化、燃料电池和其他能源产生和储存装置。在太阳能燃料装置中，含离子聚合物膜负责允许离子在电极之间的选择性传输，以保持总体电荷中性，但限制在电极上产生的氧化和还原产物的传输。在这些应用中，膜技术的改进需要新材料的开发，这将依赖于对聚合物膜结构与离子、分子和复杂混合物的传输之间关系的基本理解。本项目利用可调膜设计策略来研究含离子聚合物膜的膜结构、膜物理化学性质和膜传输行为之间的基本关系。本研究结果将为今后含离子聚合物膜的设计提供基本的结构-性能关系。该研究将培养膜科学前沿研究的本科生和研究生，并吸引STEM领域中代表性不足群体的学生。研究人员还将开发和传播实践教育和外展活动，包括通过暑期研究体验和小学教育外展，包括为高中生举办的暑期工程营，开发和传播与STEM和膜科学相关的本科生独立学习体验和探索模块。本研究的目的是阐明在含离子聚合物膜与膜结合阴离子（阳离子交换膜）中，共运输中性物质如何影响带电物质的运输。研究假设，中性物质的存在减少了膜结合的磺酸盐阴离子和渗透阴离子之间发生的静电相互作用（即Donnan排斥），导致带电溶质的渗透性增加。将合成具有系统变化的膜结构、自由体积分数和离子含量的pegda基膜，并表征膜化学对其理化性质的影响。基本的溶质-溶质和溶质-膜相互作用将系统地阐明，使用基于丙烯酸酯和二丙烯酸酯光聚合的可调合成设计策略来控制聚合物膜结构，结合离子含量和吸水率。将对中性溶质（甲醇）、离子溶质（醋酸酯）及其复杂混合物的传输特性（即渗透性、溶解度和扩散性）进行实验研究。渗透实验将使用定制的扩散池进行，该扩散池配备了ATR FTIR光谱来监测接收池的溶质浓度，从而能够同时表征多个同时的溶质浓度。这项研究将有可能影响各种应用的新膜材料的设计，例如用于水净化的材料，以及太阳能燃料装置等能源设备。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Ion-containing polymer membranes are critical components in many technologies including chemical separations, water purification, fuel cells, and other energy generation and storage devices. In solar-fuel devices, ion-containing polymer membranes are responsible for permitting the selective transport of ions between electrodes to maintain overall charge neutrality yet limit the transport of oxidation and reduction products produced at the electrodes. Improvements in membrane technology for these applications requires new material development that will rely on fundamental understanding of the relationships between polymer membrane structure and the transport of ions, molecules and complex mixtures. This project leverages a tunable membrane design strategy to investigate fundamental relationships between membrane structure, membrane physicochemical properties, and membrane-transport behavior of ion-containing polymer membranes. Results from this study will provide fundamental structure-property relations which will guide the future design of ion-containing polymer membranes. The research will train undergraduate and graduate students in cutting edge research in membrane science and engage students from underrepresented groups in STEM fields. The investigators will also develop and disseminate hands-on educational and outreach activities, including undergraduate independent study experiences and exploratory modules related to STEM and membrane science through summer research experiences and primary education outreach including summer engineering camps for high school students.The goal of this research is to elucidate how co-transporting neutral species impact the transport of charged species in ion containing polymer membranes with membrane-bound anions (cation exchange membranes). The research hypothesis is that the presence of neutral species reduces electrostatic interactions (i.e. Donnan exclusion) that occur between membrane-bound sulfonate anions and permeating anions, leading to increased permeability of the charged solute. PEGDA-based membranes with systematically varied membrane structure, fractional free volume, and ion content will be synthesized and the impact of membrane chemistry on physiochemical properties will be characterized. Fundamental solute-solute and solute-membrane interactions will be systematically elucidated using a tunable synthetic design strategy based on photopolymerization of acrylates and diacrylates to control polymer membrane structure, bound ion content, and water uptake. Transport properties (i.e. permeability, solubility, and diffusivity) will be investigated experimentally for a neutral solute (methanol), an ionic solute (acetate), and their complex mixture. Permeation experiments will be conducted using custom-built diffusion cells outfitted to monitor receiver cell solute concentrations using ATR FTIR spectroscopy enabling simultaneous characterization of multiple simultaneous solute concentrations. This research will have the potential to impact the design of new membrane materials for a variety of applications, such as materials for water purification, and energy devices such as solar fuels devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.