CDS&E: Organization and Dynamics of Charged Molecules in Heterogeneous Media

该奖项支持聚合物电解质的计算和理论研究以及教育。聚合物电解质是含有带电单元的长链状分子。它们是用于生产和储存清洁能源的新兴材料，如排放水作为废气的燃料电池电动汽车和由可充电锂离子电池供电的汽车。聚合物电解质是理想的选择，因为它们柔韧性好、重量轻、可回收，而且价格低廉。然而，聚合物燃料电池和电池的效率很低。为了优化它们的效率，至关重要的是要了解它们的结构，以及电荷或离子如何在位于终端之间和这些器件内部的聚合物电解质材料上移动。在这个项目中，PI旨在推进对不同聚合物电解质相之间复杂相互作用的基本理解，以及离子在聚合物电解质材料中的分布和运动，从而设计出纳米级“高速公路系统”，使离子能够在高性能电池和燃料电池中穿行。在材料内部形成的被称为纳米结构的分子尺度结构指导离子如何运动。预测理论和计算工具可以描述和解释聚电解质的复杂行为，有助于优化离子在材料中的传输，从而提高储能装置的效率。PI将以最近开发的方法为基础，描述聚合物电解质材料中的不均匀性对离子运动的影响，以及离子在材料中运动时的相关性。PI旨在开发一种自一致的描述，考虑到离子的复杂分布及其运动如何影响聚合物电解质材料，以及聚合物电解质的结构如何影响离子的分布及其运动。特别感兴趣的是使用分子动力学和其他计算方法来分析受不同材料及其相关电荷的界面限制的带电单元的离子传输，这是设计纳米级“高速公路系统”的重要一步，使离子能够在高性能电池和燃料电池中传播。通过该项目开发的计算工具可以解决材料设计中出现的问题，例如在生物系统和工业过程中有更广泛的应用。这些工具将有助于理解携带电荷的分子单元是如何被限制在小区域内的，这是由具有不同电子性质的不同材料构成的环境的结果。这将有助于激发操作和设计能量存储材料的创新解决方案，以及纳米流体装置。从这个项目中产生的影响将是一组研究汇编成出版物和开放获取程序，以协助研究相关理论和计算软物质问题的研究人员。该奖项支持计算和理论研究，以及聚电解质共混物和共聚物的教育，这些共聚物已被确定为高密度储能和发电设备中使用的合适候选材料。它们结合了聚合物的低挥发性和高柔韧性与携带电荷的主链的离子选择性导电性。在聚电解质共混物和带中性电荷的共聚物熔体中，由于介电常数相对较低，离子相关性可以显著降低混溶性，诱导相分离成具有不同浓度和离子顺序的纳米相。利用自一致场和液态理论的混合，PI将研究共聚物电解质形成的纳米相结构，它们的界面性质和离子电导率。聚电解质共聚物熔体中离子相关性的影响决定了其在多个长度尺度上的结构。离子分布取决于介质的介电性质和介电非均质性，这种非均质性是由离子相关性和组分的混溶程度引起的。PI将开发模型来自洽地解释这些影响。纳米相分离结构以及一维与德拜长度相当的纳米通道具有静电势，该静电势可以被通道内部的软离子结构和界面处的介电非均质性显著调制。纳米通道的离子浓度和结构对其力学性能和输运性能有显著影响。由于对称一价电解质是一种可以用泊松-玻尔兹曼理论来理解的简单的物理体系，因此目前的研究主要针对的是对称一价电解质水溶液。然而，实际应用可能涉及多价离子种类以及具有低介电常数的材料的介电界面。因此，了解电荷中性共聚物熔体结构中相关关系的影响，以确定离子如何通过纳米通道传输是至关重要的。需要确定的重要影响包括纳米结构的对称性和周期性，这在很大程度上取决于离子大小、分子量、共聚物组成和沿链的电荷分布。PI将实现包括离子相关性、分子有限尺寸和介电非均质性在内的MD模拟，以确定聚电解质共聚物熔体的结构和离子电导率。这些模拟基于真实的能量泛函，足以处理多重和弯曲界面、多价盐和不对称离子尺寸的情况，以研究软离子结构的动态演化。通过该项目开发的计算工具可以解决材料设计中出现的问题，例如在生物系统和工业过程中有更广泛的应用。这些工具将促进对带电软物质和聚合物材料的理解，并将有助于激发能量存储、软电子、纳米流体器件和其他应用领域操作和设计材料的创新解决方案。从这个项目中产生的影响将是一组研究汇编成出版物和开放获取程序，以协助研究相关理论和计算软物质问题的研究人员。

NONTECHNICAL SUMMARYThis award supports computational and theoretical research, and education on polymer electrolytes. Polymer electrolytes are long chain-like molecules that contain charged units. They are emerging materials for the production and the storage of clean energy in devices such as fuel cell electric vehicles that emit water as exhaust and vehicles powered by rechargeable lithium-ion batteries. Polymer electrolytes are ideal candidates because they are flexible, lightweight, recyclable, and inexpensive. However, polymer fuel cells and batteries have low efficiencies. In order to optimize their efficiency, it is crucial to understand their structure, and how electric charges, or ions, move across the polymer electrolyte material that lies between the terminals and inside these devices. In this project the PI aims to advance fundamental understanding of the complex interplay among different polymer electrolyte phases and the distribution of ions and their motion inside polymer electrolyte materials to enable the design of a nanoscale 'highway system' for ions to travel inside higher performance batteries and fuel cells. The formation of molecular-scale structures called nanostructures within the material guides how ions move. Predictive theoretical and computational tools that can describe and explain the complex behavior of polyelectrolytes could help optimize transport of ions through materials to increase efficiency of energy storage devices. The PI will build on a recently developed approach to describe the effect of inhomogeneities in the polymer electrolyte materials have on the ion motion and on the correlations in the motions of the ions as they move through the materials. The PI aims to develop a self-consistent description that takes into account how the complex distribution of ions and their motions affect the polymer electrolyte material and how the structure of the polymer electrolyte affects the distribution of ions and their motions. Of particular interest is the use of molecular dynamics and other computational methods to analyze ionic transport of charged units confined by interfaces with different materials and their associated electric charges, an important step toward a capability to design nanoscale 'highway systems' for ions to travel inside high performance batteries and fuel cells.Computational tools developed through this project to address problems that arise in materials design have more general application, for example in biological systems and in industrial processes. These tools will enable advances in understanding how molecular units that carry electric charge are confined in small regions as a consequence of an environment made of different materials with different electronic properties. This will help stimulate innovative solutions for manipulating and designing materials for energy storage, as well as nanofluidic devices. Among the impacts derived from this project will be a set of studies compiled into publications and open access programs to assist researchers working in related theoretical and computational soft matter problems. TECHNICAL SUMMARYThis award supports computational and theoretical research, and education on polyelectrolyte blends and copolymers which have been identified as suitable candidate materials for use in high-density energy storage and generation devices. They combine the low volatility and high flexibility of polymers with ion-selective conductivity of the charge-carrying backbone. In polyelectrolyte blends and in neutral-charged copolymer melts, ionic correlations can significantly reduce miscibility, inducing phase separation into nanophases with different concentrations and ordering of ions given that the dielectric constant is relatively low in these materials. Using a hybrid of self-consistent field and liquid state theories, the PI will investigate the nanophase structures formed by copolymer electrolytes, their interfacial properties and ion conductivity. The effect of ionic correlations in polyelectrolyte copolymer melts determines the structure at multiple length scales. The ion distribution depends on the dielectric properties of the media and on the dielectric heterogeneities that developed due to ionic correlations and to the degree of miscibility of the components. The PI will develop models to account for these effects self-consistently. Nanophase segregated structures as well as nanochannels where one dimension is comparable to the Debye length, possess an electrostatic potential that can be significantly modulated by the soft ionic structure inside the channel and by the dielectric heterogeneity at the interface. The ionic concentrations and structure of the nanochannels affect the mechanical and transport properties dramatically. Present studies mainly deal with simple symmetric monovalent electrolytes in aqueous solutions because it is a simple physical system that can be understood by Poisson Boltzmann theory. However, real applications may involve multivalent ion species as well as dielectric interfaces of materials with low dielectric constants. It is therefore crucial to understand the effect of correlations in the structure of charged-neutral copolymer melts, to determine how ions transport through nanochannels. Important effects to determine include the nanostructure symmetry and periodicity which is strongly dependent on ion sizes, molecular weight, copolymer composition and charge distribution along the chains. The PI will implement MD simulations that include ion correlations, finite size of molecules and dielectric heterogeneities to determine the structure of polyelectrolyte copolymer melts and ion conductivities. These simulations, which are based on a true energy functional, are versatile enough to treat the case of multiple and curved interfaces, multivalent salts, and asymmetric ion sizes to study the dynamical evolution of the soft ionic structure. Computational tools developed through this project to address problems that arise in materials design have more general application, for example in biological systems and in industrial processes. These tools will enable advances in understanding of charged soft matter and polymeric materials and will help stimulate innovative solutions for manipulating and designing materials for energy storage, soft electronics, nanofluidic devices, and other application areas. Among the impacts derived from this project will be a set of studies compiled into publications and open access programs to assist researchers working in related theoretical and computational soft matter problems.