Modeling Nanoscale Confinement of Fluids: Applications to Fluids in Porous Materials and Liquids Wetting Nano-structured Surfaces

智力优势：该项目针对纳米尺度约束下流体性质的分子热力学建模。在这种情况下，约束一方面是指复杂多孔材料中的流体，另一方面是指当液体与固体表面上的小尺度图案接触时，约束是由表面图案的长度尺度产生的。对于多孔材料中的流体，了解基本的热力学行为对从催化、吸附分离到膜，以及在多孔材料表征中使用吸附等应用具有重大影响。液体对多孔、结构或图案表面的界面润湿已经在许多技术中引起了相当大的兴趣，从开发防水纺织品到设计气-液-固催化反应器。最近，人们对液体接触固体的纳米技术的应用也产生了兴趣，如微流体和纳米流体、纳米光刻或“芯片实验室”技术。研究主要集中在两个方面：(i)复杂孔隙结构中流体的粗粒度模型的开发和应用。研究人员正在开发一种复杂孔隙结构流体的统一建模方法，该方法可以在单一框架中处理润湿流体（气体吸附）和非润湿流体（汞孔隙度测定）。该研究计划旨在了解这些系统的平衡状态以及滞后和伴随的动力学。（ii）了解液体如何润湿拓扑和化学图案表面。研究人员使用密度泛函理论和分子模拟来计算液滴在图案表面上的密度分布。目标是了解三相固-液-气接触的细节，以及固体表面结构对接触的影响。这些研究领域通过流体约束和界面润湿现象的共同主题基本联系在一起。在这些领域中，统计力学研究的一个中心问题是需要处理这些系统中由于几何结构的复杂性而产生的密度分布的三维性。这些模型应该允许人们在纳米尺度和介观尺度之间架起桥梁。本研究采用了平均场密度泛函理论和蒙特卡罗模拟等计算方法。更广泛的影响：该项目代表了分子热力学基础研究的一个例子，与重要的工程应用密切相关。该研究的主要影响是应用于气体吸附和汞孔隙度法表征多孔材料。这项研究正在为理解这两种重要的表征技术创建一个单一的分子建模框架。最近的纳米技术研究显示了在小尺度上理解界面的重要性。这里开发的用于研究承压流体的建模技术，侧重于三维界面结构，也可以在这一领域产生重大影响。该项目具有重要的教育成分，首先是通过研究生、博士后学者和本科生的参与。研究小组活动旨在培养学生交流其研究成果的能力，我们的研究生参与本科课程的教学，作为他们学位课程的教育要求。在国家科学基金支持下开发的材料将用于为本科生编写吸附热力学讲座和为化学工程研究生编写统计热力学课程的项目材料。该项目的特点是与工业界（Quantachrome Corporation）的研究人员合作，以及与莱比锡大学和柏林技术大学的研究小组进行国际合作。

Monson / 0649552Intellectual merit: This project is directed at the molecular thermodynamic modeling of fluid properties under nano-scale confinement. In this context, confinement refers on the one hand to the case of fluids in complex porous materials and on the other to when a liquid is in contact with a small scale patterning on a solid surface, where confinement is created by the length scale of the surface patterning. For fluids in porous materials, understanding of fundamental thermodynamic behavior has significant impact on applications ranging from catalysis to adsorption separations to membranes, as well as in the use of adsorption for porous materials characterization. The interfacial wetting of porous, structured or patterned surfaces by liquids has been of considerable interest in many technologies, ranging from the development water resistant textiles to the design of gas-liquid-solid catalytic reactors. Recently, interest is also emerging in applications in nanotechnology where liquids contact solids such as micro- and nano-fluidics,nano-lithography or "lab on a chip" technologies.The research focuses on two areas: (i) Development and application of coarse-grained models for fluids confined in complex pore structures. The investigators are developing a unified modeling approach to fluids in complex pore structures that can treat both wetting fluids (gas adsorption) and non-wetting liquids (mercury porosimetry) in single framework. The research program seeks to understand the equilibrium states of these systems as well as hysteresis and the accompanying dynamics. (ii) Understanding how liquids wet topologically and chemically patterned surfaces. The investigators use density functional theory and molecular simulations to calculate the density distributions for liquid droplets on patterned surfaces. The goal is to understand the fine details of the three-phase solid-liquid-vapor contacting and how this is influenced by the structure of the solid surface. These research areas are linked fundamentally by a common theme of fluid confinement and interfacial wetting phenomena. A central issue for statistical mechanics research in these areas is the need to deal with the three-dimensionality of the density distribution in these systems created by the complexity in the geometry. These models should allow one to bridge the nanoscopic and mesoscopic length scales. This research features several computational methods including mean field density functional theory and Monte Carlo simulation. Broader Impacts: The project represents an example of fundamental research in molecular thermodynamics that is closely linked with important engineering applications. The primary impact of the research is in application to porous material characterization using gas adsorption and mercury porosimetry. The research is creating a single molecular modeling framework for understanding both of these important characterization techniques. Recent research in nanotechnology has shown the importance of understanding interfaces at small length scales. The modeling techniques developed here for studying confined fluids, which focus on three-dimensional interfacial structure, can make a significant impact in this area also. The project has significant educational components, in the first instance through the involvement of graduate students, postdoctoral scholars and undergraduates. Research group activities are designed to develop the ability of students to communicate their research achievements, and our graduate students participate in teaching undergraduate courses as an educational requirement of their degree program. Material developed under NSF support will be used to develop lectures in adsorption thermodynamics for undergraduates and project materials for a course in statistical thermodynamics for chemical engineering graduate students. The project features collaboration with researchers in industry (Quantachrome Corporation) as well as international collaboration with research groups at the University of Leipzig and the Technical University of Berlin.