CAREER: Nonequilibrium Physics in Drying Soft Matter Solutions

非技术总结这个职业奖项支持计算和理论研究，以及软物质溶液蒸发干燥物理方面的教育。油漆是软物质解决方案的一个例子。油漆是一种颗粒悬浮液，它是悬浮在整个溶剂中的小颗粒的异质混合物。聚合物溶液是另一个例子，它是溶剂和聚合物的混合物，长链分子溶解在其中。这些软物质溶液的干燥过程提供了一种制造材料的方法，也提供了一种研究非平衡系统物理的方法。一个著名的例子是咖啡环效应，咖啡溢出，一种像油漆一样的颗粒悬浮液，在干燥后在其周围留下环状沉积物。作为另一个例子，最近在含有不同尺寸的颗粒的悬浮膜中发现了新的分层现象，在悬浮液快速干燥后，颗粒根据其尺寸形成分层层。这项研究的目的是利用计算机模拟技术和简单的物理模型来阐明颗粒悬浮液、聚合物溶液及其混合物蒸发过程中固有的颗粒集体行为，并制定出使得到的材料具有所需结构的最佳干燥条件。这种材料包括颗粒或聚合物的多层薄膜，以及以受控方式通过聚合物基质分散的颗粒填充物的复合材料。具体地说，该项目旨在回答以下问题：含有溶质混合物的溶液快速干燥后，溶解或分散的成分在干膜中是如何分布的？颗粒和聚合物在干燥过程中自然出现的浓度、温度或其他梯度下是如何迁移的？这些发现将被用来指导设计新的溶剂挥发工艺，以实现更高效的材料制造。该项目将研究纳入教育和外联活动，涉及高中、本科生和研究生、高中和大学教育工作者以及更广泛的公众。具体目标包括在弗吉尼亚理工学院建立软物质课程，用该课程培养学生和未来的劳动力，促进弗吉尼亚州软物质社区的发展，并向公众推广“通过计算、理论和实验的互补努力加速材料发现”的新兴概念。技术总结这个职业奖项支持计算和理论研究，以及软物质溶液蒸发干燥物理的教育。从胶体和聚合物溶液及其混合物中挥发溶剂是一种经常用于制备薄膜材料的工具，但我们对溶剂挥发过程如何影响最终的胶体和聚合物薄膜的结构的了解主要是基于经验，缺乏预测能力。研究部分的总体目标是利用非平衡统计力学中的工具来绘制出最佳的蒸发条件，在该条件下干燥的胶体和聚合物溶液产生具有所需结构的材料，包括分层胶体薄膜、层状聚合物薄膜和具有可控纳米粒子分散的聚合物纳米复合材料。PI采用计算/理论混合的方法，使用基于粒子的液体、胶体粒子和聚合物的描述来探索蒸发过程所固有的丰富的非平衡多体物理。主要目标是使用分子动力学技术来模拟各种软物质溶液的干燥过程，其中显式溶剂基于Lennard-Jones液体或粗粒表示的水，并揭示蒸发过程对所得材料结构的影响。用目前的实验来评估这些影响是具有挑战性的。具体地说，PI旨在阐明各种多组分软物质溶液中干燥诱导分层的物理机制，以及颗粒和聚合物对干燥过程中出现的浓度、温度、化学势和其他梯度的磷化反应。显式研究溶剂使PI能够确定隐式溶剂模型可能适用的情况，这可以为许多其他缺乏资源显式建模干燥溶液的溶剂的研究人员提供指导。该项目将研究整合到教育和推广活动中，涉及学生、教育工作者和更广泛的公众，旨在在弗吉尼亚理工大学建立软物质课程，利用该课程培养学生和未来的劳动力，促进弗吉尼亚州软物质社区的发展，并向公众推广非平衡物理和新兴的“计算思维”和“通过自组装的材料”的概念。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis CAREER award supports computational and theoretical research, and education on the physics of evaporative drying of soft matter solutions. Paint is an example of soft matter solution. Paint is a particle suspension, which is a heterogeneous mixture of little particles suspended throughout the bulk of a solvent. A polymer solution is another example, which is a mixture of a solvent and polymers, long-chain molecules, dissolved in it. The drying process of these soft matter solutions provides a way to fabricate materials and a way to investigate physics in systems out of equilibrium. A famous illustration is the coffee ring effect, where a spill of coffee, a particle suspension like paint, leaves a ring-like deposit at its perimeter after drying. As another example, novel stratification phenomena have recently been discovered in suspension films containing particles of varied sizes, where the particles are found to form stratified layers according to their sizes after the suspensions are rapidly dried. The goal of the research is to use computer simulation techniques and simple physical models to elucidate the collective behavior of particles intrinsic to the evaporation processes of particle suspensions, polymer solutions, and their mixtures, and to map out the optimized drying conditions under which the resultant materials have desired structures. Such materials include multi-layered thin films of particles or polymer and composite materials with particulate fillers dispersed through a polymer matrix in a controlled manner. Specifically, this project aims to answer the following questions: How are the dissolved or dispersed components distributed in the dry film after a solution containing a mixture of solutes is dried quickly? How do particles and polymers migrate under concentration, temperature or other gradients that naturally emerge in a drying process? The findings will be used to guide the design of new solvent evaporation processes for more efficient material fabrication. The project integrates research into education and outreach activities that involve high school, undergraduate, and graduate students, high school and college educators, and the broader public. Specific goals include establishing a soft matter curriculum at Virginia Tech, cultivating students and future workforce with this curriculum, fostering the growth of a soft matter community in Virginia, and promoting the emerging concept of “material discovery accelerated through complementary efforts in computation, theory, and experiment” to the general public.TECHNICAL SUMMARYThis CAREER award supports computational and theoretical research, and education on the physics of evaporative drying of soft matter solutions. Solvent evaporation out of colloidal and polymer solutions and their mixtures is a tool frequently used to fabricate thin film materials, but our understanding of how the evaporation process of the solvent impacts the structures of the final colloidal and polymer films is largely based on experience and lacks predictive capabilities. The overarching objective of the research component is to use tools in nonequilibrium statistical mechanics to map out the optimized evaporation conditions under which the drying colloidal and polymer solutions yield materials with desired structures, including stratified colloidal thin films, layered polymer thin films, and polymer nanocomposites with controlled dispersion of nanoparticles. Adopting a hybrid computational/theoretical approach, the PI uses particle-based descriptions of liquids, colloidal particles, and polymers to probe the rich nonequilibrium, many-body physics intrinsic to evaporation processes. The main goal is to use molecular dynamics techniques to model the drying process of various soft matter solutions with an explicit solvent based on Lennard-Jones liquids or water in coarse-grained representations, and to reveal the effects of evaporation processes on the resulting material structures. These effects are challenging to evaluate with current experiments. Specifically, the PI aims to elucidate the physics of drying-induced stratification in various multicomponent soft matter solutions and the phoretic response of particles and polymers to concentration, temperature, chemical potential, and other gradients that emerge during the drying process. Studying solvent explicitly enables the PI to identify cases where an implicit solvent model might be appropriate, which can serve as a guidance for many other researchers who lack the resources to model a solvent explicitly for drying solutions. The project integrates research into education and outreach activities that involve students, educators, and the broader public and aim to establish a soft matter curriculum at Virginia Tech, to cultivate students and future workforce with this curriculum, to foster the growth of a soft matter community in Virginia, and to promote nonequilibrium physics and the emerging concepts of “computational thinking” and “materials via self-assembly” to the general public.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.