Collaborative Research: Measurement, Simulation, and Theory of Molecular Connectivity Effects on Nanoscale Interfacial Rheology of Glass-Forming Fluids

如果你把许多现代材料放大观察，你会发现它们的基本结构只有几百个原子那么宽，同时它们又以巨大的意大利面状的化学链连接在一起。这些“聚合纳米材料”为改变我们的生活、经济和国防的新技术打开了大门。它们前景光明的一个主要原因也是它们面临的最大挑战：神秘的是，这些聚合物纳米材料的界面使它们的行为与传统材料截然不同。这个奖项旨在解决这个谜团的一个关键部分：为什么这些材料在这些微观界面附近的变形非常不同？我们如何设计它们来控制这种变形行为，从而更经济地制造它们，进一步改善它们的性能，最终实现新的技术进步？这些问题将通过放大到纳米尺度的实验来回答，观察这些材料是如何流动和变形的。与此同时，超级计算机模拟将可视化分子运动是如何导致这种变形的。最终，这些结果将推动解释这些材料行为的理论的发展，并使材料工程师能够改进他们的设计并推动新技术的进步。这项工作将与普林斯顿大学和南佛罗里达大学的联合推广项目相结合，让不同的高中学生接触到界面的实验和计算研究。该奖项将建立对玻璃形成流体界面流变响应的纳米级梯度的预测理论理解。这些梯度至少部分来自于界面处玻璃化转变温度梯度的存在。然而，当这个梯度被大分子跨越时，特别是在存在表面吸附的情况下，尚不清楚它是如何控制流变反应的改变的。工作旨在(1)建立纳米尺度自由表面附近线性流变变化的理论，(2)将该理论扩展到处理与复合材料和多相流体相关的埋藏界面，以及(3)建立改变近界面流变响应的新策略。为了支持新的理论发展，一种测量时间分辨纳米蠕变的实验计量方法将与流变学和链动力学的梯度模拟相结合。这项工作建立的预测性理解将改变对界面丰富流体流动的理解、预测和设计，如纳米颗粒负载流体、薄膜和纳米结构多相流体。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。

If you zoomed into many of the modern materials that empower energy storage, enable water purification, or even make up the tires on your car, you would find that their essential structures are only hundreds of atoms across, and at the same time are chemically connected in vast spaghetti-like strands. These “polymeric nanomaterials” open the door to new technologies that can transform our life, economy, and national defense. A major reason for their promise is also their greatest challenge: mysteriously, the interfaces that pervade these polymeric nanomaterials cause them to behave dramatically differently than traditional materials. This award aims to solve a key piece of this mystery: why do these materials deform very differently in the vicinity of these microscopic interfaces? How can we design them to control this deformation behavior and thus fabricate them more economically, further improve their properties, and ultimately enable new technological advances? These questions will be answered via experiments that zoom in to the nanometer scale to observe how these materials flow and deform. At the same time, supercomputer simulations will visualize how molecules’ movements underlie this deformation. Ultimately, these results will drive the development of a theory that explains these materials’ behavior and empowers material engineers to improve their design and drive new technological advances. The effort will be integrated with a joint Princeton and University of South Florida outreach program exposing diverse high school students to experimental and computational research on interfaces.This award will establish a predictive theoretical understanding of nanoscale gradients in rheological response at interfaces in glass-forming fluids. These gradients emanate at least in part from the presence of a glass transition temperature gradient at interfaces. However, when this gradient is spanned by large molecules, particularly in the presence of surface adsorption, it is not clear how it controls alterations in rheological response. Work aims to (1) establish a theory of alterations in linear rheology in the nanoscale vicinity of free surfaces, (2) extend this theory to treat buried interfaces relevant to composites and multi-phase fluids, and (3) establish a new strategy for altering near-interface rheological response. To support new theory development, an experimental metrology to measure time-resolved nanocreep will be combined with simulations probing gradients in rheology and chain dynamics. Predictive understanding established by this work will transform the understanding, prediction, and design of flow of interfacially-rich fluids, such as nanoparticle-laden fluids, thin films, and nanostructured multiphase fluids.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.