Collaborative Research: Thermodynamics, Grain Structure and Ion Transport in Block Copolymer/Salt Mixtures

非技术描述：与清洁能源相关的电化学设备，如锂电池，通常依靠聚合物膜在电极之间传导离子。了解限制离子传输的因素将有助于合理设计更好的膜，最终导致更高效的设备。该奖项专门研究锂离子通过一类被称为嵌段共聚物的聚合物的传输。这些分子自组装成双连续的导电区和非导电区。磁区具有特定的几何形状或形态，例如在非导电基质中填充的六角形导电圆柱体或交替的导电和非导电层。盐的添加对形态有影响；给定的共聚物在给定的盐浓度下可能表现出一种形态，而在较高的盐浓度下可能表现出另一种形态。一个目标是确定盐对形态的影响。样品的加工条件会在形态上造成缺陷。膜的形态和缺陷决定了离子的导电性，因此表征膜的形态和缺陷是制备更好膜的重要第一步。这项工作是朝着在美国建立一个可持续的清洁能源平台迈出的一步。除了拟议的科学工作外，其中一名调查人员还将与伯克利STEM(科学、技术、工程和数学)中心合作，开发旨在帮助有才华的低收入第一代大学生发展成为科学家和工程师的课程。另一名调查员参与了对纽约布鲁克林高中生的广泛科技宣传。技术说明：这项研究的重点是通过阴离子聚合合成的聚苯乙烯-聚氧乙烯(PS-PEO)嵌段共聚物与双三氟甲基磺酰亚胺的混合物，双三氟甲基磺酰亚胺是一种经常用于含有聚合物电解液的电池的盐。电子显微镜、小角X射线散射和去偏振光散射将被用来确定这些材料中有序-无序和有序-有序相变的性质。盐离子在PEO微相中的排列以及有序相和无序相共存的窗口宽度是特别感兴趣的。样品的电导率将使用交流阻抗谱进行现场测量，而结构则通过X射线或光散射研究来确定。测量范围广泛，包括嵌段共聚物组成、盐浓度、温度和热处理条件。该项目产生的数据将检验最近关于嵌段共聚物/盐混合物相行为的理论。计划中的工作具有相当大的智力价值，因为该项目产生的数据将提供基本的洞察，了解支持电化学设备用新型纳米结构材料结构、热力学和传输之间耦合的因素。参与该项目的研究生将接受与可持续能源利用相关的科学培训。拟议的研究具有多学科性质，包括聚合物合成、表征和电化学测量，将为学生提供丰富的学习环境。此外，STEM还在加利福尼亚州伯克利和纽约州布鲁克林进行了STEM推广。

NON-TECHNICAL DESCRIPTION:Electrochemical devices related to clean energy such as lithium batteries often rely on polymer membranes to conduct ions between the electrodes. Understanding the factors that limit ion transport will enable the rational design of better membranes that will ultimately lead to more efficient devices. This award specifically examines lithium ion transport through a class of polymers known as block copolymers. These molecules self-assemble to give bicontinuous conducting and non-conducting domains. The domains have specific geometries or morphologies such as hexagonally packed conducting cylinders in a non-conducting matrix or alternating conducting and non-conducting layers. The addition of salt has an effect on the morphologies; a given copolymer may exhibit one morphology at a given salt concentration and another at a higher salt concentration. One objective is to establish the effect of salt on morphology. Sample processing conditions can create defects in the morphology. The morphology and the defects will dictate ionic conductivity, and therefore characterizing the morphology and the defects is an important first step in making better membranes. This work is a step toward building a sustainable clean-energy platform in the US. In addition to the proposed scientific work, one of the investigators will develop courses aimed at helping talented low-income, first-generation-college students develop into scientists and engineers in collaboration with the Berkeley Center for STEM (Science Technology Engineering and Math). The other investigator is involved in broad science-and-technology outreach to high school students in Brooklyn, New York. TECHNICAL DESCRIPTION:This research focuses on mixtures of polystyrene-polyethyleneoxide (PS-PEO) block copolymers, synthesized by anionic polymerization, and bis-trifluoromethylsulfonimide, a salt that is often used in batteries containing polymer electrolytes. Electron microscopy, small-angle X-ray scattering and depolarized light scattering will be used to determine the nature of the order-disorder and order-order phase transitions in these materials. The arrangement of the salt ions in the PEO microphases and the width of windows where ordered and disordered phases coexist are of particular interest. In-situ conductivity measurements will be made on samples using ac impedance spectroscopy while structure is determined by either X-ray or light scattering studies. Measurements will be made over a wide range of block copolymer compositions, salt concentration, temperature, and annealing conditions. The data generated by the project will test recent theories on phase behavior of block copolymer/salt mixtures. The planned work is of considerable intellectual merit as the data generated by the project will provide fundamental insight into the factors that underpin the coupling between structure, thermodynamics, and transport in an emerging class of nanostructured materials for electrochemical devices. The graduate students working on this project will receive scientific training related to sustainable energy use. The multidisciplinary nature of the proposed research, which includes polymer synthesis, characterization, and electrochemical measurements, will provide the students with a rich learning environment. It is coupled with STEM outreach at Berkeley, CA and Brooklyn, NY.