Studies on Polymeric Glasses, Melts, and Mixtures: Connecting Microscopic Character with Observable Behaviour

非技术摘要我们在世界上看到的大部分东西都是由相对较少的元素组成的。它们结合在一起创造了具有如此巨大行为范围的各种物质这一事实证明，化学成分和可观察到的物理性质之间的线既不短也不直。本研究的目标主要集中在大分子及其混合物上。大分子，或聚合物，是小分子‘重复单元’连接的大分子。一个例子是由乙烯制成的聚乙烯，它被用于生产塑料袋、薄膜和瓶子(以及其他东西)。聚乙烯只含有两种元素，碳和氢；与聚乙烯具有不同性质的其他聚合物可以由相同的两种元素制成。即使是这个简单的例子，单从它们的化学“配方”来预测所有这些聚合物的性质也不是简单的。除了物质的化学性质外，材料的性质还取决于它的配方。例如，无论是浇注在薄膜中、制成薄膜，还是批量加工，都会影响材料对温度、压力和其他成分的反应。在这项由该提议资助的研究中，将使用理论和计算机模拟相结合的方法，在复杂材料的微观性质和特性与其块体和薄膜特性之间建立新的联系。开发的理论工具将能够从对纯成分的表征(使用实验数据)引导到分析和预测该物质在不同条件下的行为，并与不同的合作伙伴混合。这项研究的另一个方面涉及在处理薄膜甚至膜时，相对于大块样品，大分子的行为如何变化。例如，有证据表明，一些聚合物在薄膜中的熔化温度比在块体中时低得多；有趣的是，当薄膜加载到固体衬底上时，这种效应可以被抵消，甚至逆转，这取决于聚合物和衬底的化学性质。PI将探索样品的物理形式及其邻居的选择如何影响其一些可观察到的特性；这种洞察力对于涉及薄膜聚合物的无数应用来说是关键。在人力资源方面，这项研究将为本科生、研究生和博士后研究员创造持续参与的机会，特别是针对本科生女性。这项工作将创造新的机会，通过讲座、海报和出版物与科学公众建立联系，并与普通公众进行接触。这项研究由材料研究部和化学部共同资助。技术总结聚合物组分可以以受控的方式混合、分层或相分离，以生产复杂的新材料。这种体系的性质既取决于所选聚合物的微观化学性质，也取决于它们的使用形式，例如，以块状或作为膜、膜或复合材料的形式使用。因此，了解化学组分和分子式对宏观性质的贡献是很重要的。这项研究将为在一系列情况下帮助驱动各种凝聚态转变的分子特征提供基本的见解。这些工具将分析统计力学理论与模拟方法相结合。感兴趣的体系包括尺寸从小到聚合物的分子，从玻璃态到熔融到(如果适用)蒸汽的状态，设置范围从单组分到多组分体系，从支撑膜到层状膜，从溶液到混合物。这些属性包括平衡性和动态性，后者与玻璃化过程有关。特别感兴趣的体系包括玻璃、聚合物熔体、溶液和混合物。在薄膜的情况下，将研究支撑膜、独立膜和多层膜。多种方法的使用将为交叉检查不同的战略提供机会，并将每种战略的结果与实验进行比较。这项研究将为复杂系统在不同环境中的性质创造新的见解，并将产生仅基于纯组件性质对混合物行为进行实质性预测的工具。此外，所述不同领域的进展将在它们重叠的领域创造机会。例如：了解聚合物混合物从块状到薄膜的行为变化，研究超临界二氧化碳在离子液体中的溶解度。针对更大的科学界和更普通的公众的社会效益将从这里描述的工作中获得。新的方法将扩大软物质社区的范围，使其能够应用拟议的工作成果。这一范围的扩大将得到发布在该组织网站上的计算工具的帮助，这些工具是为临时的科学用户编写的。在人力资源方面，这项研究将为本科生、研究生和博士后研究员创造持续参与的机会，特别是针对本科生女性的努力。这项工作将创造新的机会，通过讲座、海报和出版物与科学公众建立联系，并与公众进行接触。这项研究由材料研究部和化学部共同资助

Nontechnical SummaryMost of what we see in the world is made up of a relatively small number of elements. The fact that they combine together to create such a variety of matter with such an enormous range of behavior provides evidence that the line between chemical constituency and observable physical properties is neither short nor straight. The research targeted by this study focuses largely on macromolecules and their mixtures. Macromolecules, or polymers, are large molecules that result from the connection of small molecule 'repeat units'. One example is polyethylene, made from ethylene, which is used to produce (among other things) plastic bags, films, and bottles. Polyethylene contains only two elements, carbon and hydrogen; other polymers, having different properties relative to polyethylene, can be made from the same two elements. Even for this simple example, it is not straightforward to predict the properties of all of these polymers from their chemical 'recipe', alone.In addition to the chemical nature of a substance, the properties of a material can depend on how it is formulated. For example, whether it is cast in a film, made into a membrane, or processed in bulk, influences how the material responds to temperature, pressure, and the presence of other constituents. In the research funded through this proposal a combination of theory and computer simulation will be used to create new connections between the microscopic nature and characterization of complex materials and their bulk and film properties. Developed theoretical tools will be capable to lead from the characterization of a pure component (using experimental data) to analysis and prediction of how that substance will behave under varying conditions, and mixed with different partners. Another aspect of this research deals with how the behavior of a macromolecule changes when dealing with a thin film or even a membrane, relative to a bulk sample. For example, there is evidence that some polymers melt at significantly lower temperatures when they are thin films than when in the bulk; intriguingly, this effect can be nullified or even reversed when the film is loaded onto a solid substrate, depending on the chemical nature of the polymer and the substrate. The PI will explore how the physical format of the sample, and the choice of its neighbors, affects some of its observable properties; such insight is key for the myriad applications that involve thin film polymers.In terms of human resources, the research will create continuing opportunities for involvement by undergraduates, graduate students, and postdoctoral fellows, with particular efforts aimed towards undergraduate women. This work will foster new opportunities for connecting with the scientific public, via talks, posters, and publications, and for outreach to the general publicThis research is co-funded by the Division of Materials Research and the Chemistry DivisionTechnical SummaryPolymeric components may be blended, layered, or phase separated in a controlled fashion, in order to produce sophisticated new materials. The properties of such systems depend both on the microscopic chemical nature of the polymers chosen, as well as the form in which they are used, for example, in the bulk, or as films, membranes, or composites. It is therefore important to understand how both chemical constituency and formulation contribute to macroscopic properties.This research will provide fundamental insight as to the molecular features that help drive a variety of condensed matter transitions under a range of circumstances. The tools combine analytic statistical mechanical theory with simulation methods. The systems of interest comprise molecules ranging in size from small to polymeric, states ranging from glassy to melt to (where applicable) vapor, The setups range from single to multicomponent systems, from supported to layered films, from solutions to blends. The properties encompass both equilibrium and dynamic, the latter associated with the process of glassification. Systems of particular interest include glasses, and polymer melts, solutions, and blends. In the case of thin films, supported, freestanding films, and multi-layered films will all be investigated. The use of multiple approaches will provide opportunity for cross checking the different strategies, as well as comparing the results of each to experiment. The research will create new insight regarding the properties of complex systems in different environments, and will produce tools for making substantive predictions about mixture behavior based on pure component properties, alone. In addition, progress in the different areas described will create opportunities in areas where they overlap. Examples include: understanding the changes in polymer mixture behavior going from the bulk to a thin film, and studying the solubility of supercritical carbon dioxide in ionic liquids.Societal benefits aimed both at the larger scientific community and the more general public will accrue from the work described here. New methods will expand the range of soft matter communities able to apply the results of the work proposed. This extended reach will be aided by computational tools written with casual, scientific users in mind, posted on the group website. In terms of human resources, the research will create continuing opportunities for involvement by undergraduates, graduate students, and postdoctoral fellows, with particular efforts aimed towards undergraduate women. This work will foster new opportunities for connecting with the scientific public, via talks, posters, and publications, and for outreach to the general public.This research is co-funded by the Division of Materials Research and the Chemistry Division