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

我们在世界上看到的大部分东西都是由相对少量的元素组成的。它们结合在一起，创造出如此多种多样、行为范围如此之广的物质，这一事实证明，化学成分与可观察到的物理性质之间的界限既不短也不直。本研究的研究目标主要集中在大分子及其混合物上。大分子或聚合物是由小分子“重复单元”连接而成的大分子。聚乙烯就是一个例子，它是由乙烯制成的，用于生产塑料袋、薄膜和瓶子等。聚乙烯只含有两种元素，碳和氢；其他与聚乙烯性质不同的聚合物也可以由这两种元素制成。即使对于这个简单的例子，仅从它们的化学“配方”来预测所有这些聚合物的性质也不是直截了当地的。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，它是浇铸成薄膜，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。在通过该提案资助的研究中，理论和计算机模拟的结合将用于在复杂材料的微观性质和表征及其体积和薄膜特性之间建立新的联系。开发的理论工具将能够从纯成分的表征（使用实验数据）到分析和预测该物质在不同条件下的行为，以及与不同的伙伴混合。这项研究的另一个方面是研究相对于大块样品，当处理薄膜甚至薄膜时，大分子的行为是如何变化的。例如，有证据表明，一些聚合物在薄膜状态下的熔化温度明显低于在散装状态下的熔化温度；有趣的是，当薄膜被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将探索样本的物理格式及其邻居的选择如何影响其一些可观察属性；这种洞察力是涉及薄膜聚合物的无数应用的关键。在人力资源方面，这项研究将为本科生、研究生和博士后创造持续参与的机会，并特别针对女本科生。这项工作将通过讲座、海报和出版物，为与科学公众建立联系提供新的机会，并向公众推广。这项研究由材料研究部和化学部共同资助。技术摘要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。这类系统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，是整体使用，还是作为薄膜、膜或复合材料。因此，了解化学成分和配方如何影响宏观性质是很重要的。这项研究将为分子特征提供基本的见解，这些特征有助于在一系列情况下驱动各种凝聚态物质的转变。该工具将分析统计力学理论与仿真方法相结合。感兴趣的系统包括从小到聚合物的分子，从玻璃到熔融到（适用时）蒸汽的状态，设置范围从单组分到多组分系统，从支撑到层状膜，从溶液到混合物。这些性质包括平衡和动态，后者与玻璃化过程有关。特别感兴趣的系统包括玻璃、聚合物熔体、溶液和混合物。在薄膜的情况下，支持的、独立的薄膜和多层薄膜都将被研究。多种方法的使用将为交叉检查不同的策略提供机会，并将每种策略的结果与实验进行比较。这项研究将对不同环境下复杂系统的特性产生新的见解，并将产生工具，仅基于纯组分特性对混合行为进行实质性预测。此外，上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体到薄膜的行为变化，以及研究超临界二氧化碳在离子液体中的溶解度。这里描述的工作将为更大的科学界和更广大的公众带来社会效益。新方法将扩大软物质群落的范围，使其能够应用所提出的工作结果。这个扩展的范围将会得到一些计算工具的帮助，这些工具是为随意的、科学的用户编写的，并发布在小组网站上。在人力资源方面，这项研究将为本科生、研究生和博士后创造持续参与的机会，并特别针对女本科生。这项工作将通过讲座、海报和出版物，为与科学公众建立联系提供新的机会，并扩大与公众的联系。这项研究是由材料研究部和化学部共同资助的

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