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，通常依赖于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使更好的膜的合理设计，最终导致更有效的设备。 该奖项专门研究锂离子通过一类称为嵌段共聚物的聚合物的传输。 这些分子自组装以产生双连续导电和非导电域。 域具有特定的几何形状或形态，例如在非导电基质中的六边形填充的导电圆柱体或交替的导电层和非导电层。 盐的添加对形态有影响;给定的共聚物可以在给定的盐浓度下表现出一种形态，而在更高的盐浓度下表现出另一种形态。 一个目的是确定盐对形态的影响。样品处理条件可在形态学中产生缺陷。形态和缺陷将决定离子电导率，因此表征形态和缺陷是制造更好膜的重要第一步。 这项工作是在美国建立可持续清洁能源平台的一步。 除了拟议的科学工作，其中一名研究人员将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，与伯克利STEM中心（科学技术工程和数学）合作。 另一位研究人员参与了纽约布鲁克林高中学生的广泛科学和技术推广活动。 技术描述：这项研究的重点是通过阴离子聚合合成的聚苯乙烯-聚氧化乙烯（PS-PEO）嵌段共聚物和双三氟甲基磺酰亚胺（一种常用于含有聚合物电解质的电池中的盐）的混合物。 电子显微镜，小角X射线散射和去偏振光散射将用于确定这些材料中的有序-无序和有序-有序相变的性质。 PEO微相中的盐离子的排列以及有序相和无序相共存的窗口的宽度特别令人感兴趣。 原位电导率测量将使用交流阻抗谱对样品进行，而结构则通过X射线或光散射研究确定。 将在宽范围的嵌段共聚物组合物、盐浓度、温度和退火条件下进行测量。 该项目产生的数据将测试嵌段共聚物/盐混合物相行为的最新理论。 计划中的工作是相当大的智力价值，因为该项目产生的数据将提供基本的洞察力的因素，支持结构，热力学和运输之间的耦合，在新兴的一类纳米结构材料的电化学设备。 参与该项目的研究生将接受与可持续能源利用有关的科学培训。拟议研究的多学科性质，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。 它与加州伯克利和纽约布鲁克林的STEM外展活动相结合。

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.