Collaborative Research: Mechanistic understanding and control of soft interfacial nanorheology from molecular simulations and nanoresolved experiments

从更持久、更安全的电池到用于飞机和汽车车身的强而轻的复合材料，许多材料可以打开未来技术的大门，包括纳米尺度的结构。这些材料不是由单一的均匀物质组成的。相反，这些“纳米结构”材料由大量不同的交替畴组成，每个畴的厚度都比人类头发的厚度小1000倍。通过适当的设计，这些复合材料有可能将多种材料的最佳性能结合在一起。然而，研究人员发现，纳米结构材料的性能不仅取决于纳米级畴的组成，还取决于畴之间的界面。这些接口的行为太小，无法用当前的工具直接表征，仍然是未知的。该合作奖将支持分子运动的实验和计算机模拟，将重点放在这些界面上，以了解其独特属性的起源。该项目将确定这些界面变形与周围材料的不同之处，以及如何设计界面变形以产生性能更好的材料。该研究团队将让高中生和本科生在阿克伦大学和普林斯顿大学进行综合研究，加速对新材料的理解和发现，同时扩大美国的技术劳动力。本项目旨在1)建立对聚合物/聚合物界面纳米流变性能梯度及其与分子结构的联系的机制理解；2)通过引入纳米颗粒表面活性剂，开创一种合理控制聚合物/聚合物界面附近流变性能和力学的新策略。实现这些目标的核心挑战是长期以来无法直接解决软界面附近流变响应的纳米级梯度。这项研究将通过高通量分子动力学模拟（Simmons）和实验（Priestley）之间的反馈回路来克服这一挑战。实验将结合层分辨荧光光谱和一种新的非接触剪切流变学方法，使聚合物界面附近流变特性梯度的纳米级分辨率成为可能。模拟将包括高速粗粒度模拟和化学逼真的全原子模拟。通过系统地探测聚合物和界面性质的矩阵，模拟和实验将连接界面热力学、段动力学和聚合物/聚合物界面附近的流变响应。这些结果将与一系列模拟和实验相结合，探索纳米颗粒表面活性剂对界面变形的影响，从而建立一种新的基于机制的策略，通过靶向引入纳米颗粒表面活性剂来控制界面流变响应。最终，这项工作的结果将加速具有目标界面特性和变形的材料的设计，使新型纳米结构聚合物的应用范围从下一代电池到分离膜到轻质结构材料。除了让不同层次的学生参与跨机构的培训项目外，PI还将通过在全国会议上联合组织一个研讨会来扩大这项研究的影响，该研讨会的重点是连接聚合物和界面现象研究团体。

CBET 1705738/1706012PIs: Simmons, David S./Priestly, Rodney D.From longer-lasting and safer batteries to strong and lightweight composites for use in airplanes and automobile bodies, many of the materials that could open the door to tomorrow's technologies incorporate structure on the nanometer scale. These materials are not composed of single uniform substance. Instead, these "nanostructured" materials consist of vast numbers of distinct alternating domains, each a thousand times smaller than the thickness of a human hair. With the proper design, these composites have the potential to combine the best properties of multiple materials into one. However, researchers have found the performance of nanostructured materials depends not only on the composition of the nanoscale domains, but also on the interfaces between the domains. The behavior of these interfaces, which are too small to characterize directly with current tools, remains unknown. This collaborative award will support experiments and computer simulations of molecular motion that will focus on these interfaces to understand the origins of their unique properties. The project will determine how these interfaces deform differently than the surrounding materials and how the interfacial deformation can be designed to yield materials with improved performance. The research team will engage high school and undergraduate students in an integrated research experience spanning the University of Akron and Princeton University, accelerating the understanding and discovery of new materials while broadening the U.S. technology workforce.This project aims to 1) establish a mechanistic understanding of gradients in nanoscale rheological properties at polymer/polymer interfaces and their connection to molecular structure, and 2) pioneer a new strategy for the rational control of rheology and mechanics near polymer/polymer interfaces via the introduction of nanoparticle surfactants. A central challenge in accomplishing these goals has been a longstanding inability to resolve directly nanoscale gradients in rheological response near soft interfaces. This research will overcome this challenge via a feedback loop between high-throughput molecular dynamics simulations (Simmons) and experiments (Priestley). Experiments will combine layer-resolved fluorescence spectroscopy with a novel non-contact shear rheology method that enables nanoscale resolution of gradients in rheological properties near polymer interfaces. Simulations will incorporate high-speed coarse-grained simulations and chemically-realistic all-atom simulations. By systematically probing a matrix of polymer and interfacial properties, simulations and experiments will interconnect interfacial thermodynamics, segmental dynamics, and rheological response near polymer/polymer interfaces. These results will be combined with a matrix of simulations and experiments probing the effect of nanoparticle surfactants on interfacial deformation to establish a new mechanism-based strategy for control of interfacial rheological response via the targeted introduction of nanoparticle surfactants. Ultimately, results from this work will accelerate design of materials with targeted interfacial properties and deformation, enabling new nanostructured polymers for applications ranging from next-generation batteries to separations membranes to lightweight structural materials. In addition to engagement of students over a range of levels in a cross-institution training program, the PI's will extend the impact of this research through joint organization of a symposium at a national meeting focused on bridging polymer and interfacial phenomena research communities.