Conductivity in Nanostructured Precise Polymers

第1部分：非技术概述电池，特别是便携式电子设备的电池，可能含有易燃液体，因此当电池损坏时，可能会引起火灾。为了降低这种安全风险，电池包括额外的外壳和安全功能，虽然这提高了操作过程中的安全性，但这种策略也增加了电池的尺寸和重量。另一种策略是用一层塑料膜代替易燃液体，这种塑料膜允许离子（如锂）通过，而不允许电子通过。Winey教授的团队一直在研究单离子导电聚合物，这种聚合物在电池应用和其他膜应用中可能很有价值。在之前由美国国家科学基金会资助的研究中，他们发现了当活性化学基团均匀地沿线性聚合物分子排列时，会产生各种新的纳米级结构。其中一种纳米级结构是离子和结晶聚合物的交替层状排列，最近被发现在水合作用下具有特殊的质子传输特性。为了利用这一发现，PI建立了新的聚合物膜设计规则，并与合成化学家建立了多次合作，将这些设计概念纳入新的聚合物中。Winey的团队将探索这些新设计聚合物的纳米级结构和导电性，作为其聚合物化学和加工的功能，以完善和扩展其单离子导电聚合物膜的设计规则。鉴于当前与清洁水、能源储存和能源转换相关的社会挑战，该项目提供的基本理解将产生重要的社会影响。人们对离子单体和其他具有酸、离子和极性基团的聚合物有浓厚的兴趣，因为它们具有选择性输送带电物质的潜在能力，这与电池、水净化技术和燃料电池有关。固体聚合物电解质领域的主流研究方向集中在两类均匀材料上，其中离子均匀分布在整个材料中：盐混合聚合物和单离子导体。在这些材料系统中普遍存在的设计策略是基于离子电导率与链动力学和离子必须从它们的反离子分离的理解。不幸的是，这些方法在开发合适的聚合物基电解质方面只取得了有限的成功。Winey的团队正在探索另一种假设，即当离子被隔离成空间连续的纳米级聚集体并且离子与它们的反离子分离时，聚合物中的高效离子导电性可以广泛实现。该项目建立在PI和合作者的一个有希望的结果之上，其中每21个碳上恰好有磺酸基团的水合精密聚乙烯的质子导电性略高于商业膜。这种精确的聚乙烯自组装成纳米级的层，排列着酸基团，并由结晶烷基间隔层隔开。高质子导电性证明，导电质子与慢得多的聚合物骨架的运动解耦。拟议的项目将在这一单一发现的基础上进行扩展，以确立拟议的替代假设的优点。计划中的研究结合了电导率测量、结构表征和分子动力学模拟，使用新的纳米结构精确聚合物严格质疑这一假设。所提出的烷基聚酯磺酸盐和远螺旋低聚物预计具有指导层状聚集体组装的结晶域；这些层状形态将在交错电极上排列成薄膜，以探索电导率的基本原理。随机渗透结构的精密聚乙烯与短碳间隔也将进行研究。PI和她的团队将与一组未获资助的合作者：Stefan Mecking教授（康斯坦茨大学）、Justin Kennemur教授（佛罗里达州立大学）、Paul Nealey教授（芝加哥大学）、Amalie Frischknecht博士（桑迪亚大学）和Mark Stevens博士（桑迪亚大学）。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。

PART 1: NON-TECHNICAL SUMMARYBatteries, particularly those for portable electronic devices, can contain flammable liquids, such that when a battery is damaged a fire can ensue. To mitigate this safety risk, batteries include additional housing and safety features, and while this improves safety during operation, this strategy also increase the size and weight of the battery. An alternative strategy is to replace the flammable liquid with a plastic membrane that allows ions, such as lithium, to pass through without allowing electrons to pass. Prof. Winey's group has been studying single-ion conducting polymers that could be valuable for battery applications and for other membrane applications. In previous NSF-funded work they have uncovered a variety of new nanoscale structures that arise when the active chemical groups are evenly placed along a linear polymer molecule. One of these nanoscale structures, an alternating layered arrangement of ions and crystalline polymer, was recently found to have exceptional proton transport properties when hydrated. To capitalize on this finding, the PI has established new design rules for polymer membranes and built multiple collaborations with synthetic chemists who are incorporating these design concepts into new polymers. Winey's group will explore the nanoscale structures and conductivities of these newly designed polymers as a function of their polymer chemistry and processing to refine and extend their design rules for single-ion conducting polymer membranes. Given the current societal challenges related to clean water, energy storage and energy conversion, the fundamental understanding afforded by this project will have an important societal impact. PART 2: TECHNICAL SUMMARYA strong interest in ionomers and other polymers with acid, ionic and polar groups is fueled by their potential ability to selectively transport charged species, which is relevant to batteries, water purification technologies, and fuel cells. The prevailing research directions in the field of solid polymer electrolytes have consolidated around two general classes of homogeneous materials wherein the ions are uniformly distributed throughout the material: polymers mixed with salts and single-ion conductors. The ubiquitous design strategy in these materials systems is based on the understanding that ion conductivity is associated with chain dynamics and ions must be dissociated from their counterion. Unfortunately, these approaches have only limited success in developing suitable polymer-based electrolytes. Winey's group is exploring an alternative hypothesis, namely that efficient ion conductivity in polymers can be broadly achieved when the ions are sequestered into spatially-continuous nanoscale aggregates and the ions dissociate from their counterions. This project builds upon a promising result from the PI and collaborators wherein proton conductivity of a hydrated precise polyethylene with sulfonic acid groups on exactly every 21st carbon is somewhat higher than a commercial membrane. This precise polyethylene self-assembled into nanoscale layers lined with the acid groups and separated by a crystalline alkyl spacer. The high proton conductivity is evidence that the conducting protons are decoupled from the motion of the much slower polymer backbones. The proposed project will expand upon this singular finding to establish the merits of the proposed alternative hypothesis. The planned research combines conductivity measurements, structural characterization, and molecular dynamics simulations to rigorously interrogate this hypothesis using new nanostructured precise polymers. The proposed alkyl polyester sulfonates and telechelic oligomers are expected to have crystalline domains that direct the assembly of layered aggregates; these layered morphologies will be aligned in thin films on interdigitated electrodes to explore the fundamentals of conductivity. Random percolated structures in precise polyethylenes with short carbon spacers will also be investigated. The PI and her group will undertake this project with a set of unfunded collaborators: Prof. Stefan Mecking (Konstanz), Prof. Justin Kennemur (Florida State University), Prof. Paul Nealey (U Chicago), Dr. Amalie Frischknecht (Sandia), and Dr. Mark Stevens (Sandia). .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.