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

我们在世界上看到的大多数东西都是由相对较少的元素组成的。它们联合收割机结合在一起，创造出各种各样的物质，具有如此广泛的行为，这一事实证明，化学成分和可观察到的物理性质之间的界限既不短也不直。 本研究所针对的研究主要集中在大分子及其混合物。 大分子或聚合物是由小分子“重复单元”连接而成的大分子。一个例子是聚乙烯，由乙烯制成，用于生产（除其他外）塑料袋，薄膜和瓶子。 聚乙烯只含有两种元素，碳和氢;其他聚合物，相对于聚乙烯具有不同的性能，可以由相同的两种元素制成。 即使对于这个简单的例子，仅仅从它们的化学“配方”来预测所有这些聚合物的性质也是不简单的。除了物质的化学性质之外，材料的性质还取决于它的配制方式。例如，无论是浇铸成膜，制成膜，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与其体积和薄膜性质之间建立新的联系。 开发的理论工具将能够从纯成分的表征（使用实验数据）引导到分析和预测该物质在不同条件下以及与不同伙伴混合时的行为。 这项研究的另一个方面涉及当处理薄膜甚至膜时，相对于大量样品，大分子的行为如何变化。例如，有证据表明，一些聚合物在薄膜时比在本体中时在显著更低的温度下熔化;有趣的是，当薄膜被加载到固体基底上时，这种效应可以被抵消甚至逆转，这取决于聚合物和基底的化学性质。PI将探索样品的物理形式及其相邻物的选择如何影响其可观察的性质;这种洞察力对于涉及薄膜聚合物的无数应用至关重要。在人力资源方面，该研究将为本科生、研究生和博士后研究员创造持续参与的机会，特别是针对本科女性的努力。 这项工作将促进新的机会，通过讲座，海报和出版物与科学公众联系，并推广到一般公众这项研究是由材料研究部和化学部共同资助的技术摘要聚合物成分可以混合，分层，或以受控的方式相分离，以生产复杂的新材料。 这些系统的性能取决于所选聚合物的微观化学性质，以及它们使用的形式，例如，散装，或作为薄膜，膜或复合材料。 因此，重要的是要了解化学成分和配方如何有助于宏观性质。这项研究将提供基本的见解，以分子特征，帮助驱动各种凝聚态物质在一系列情况下的转变。该工具结合了联合收割机分析统计力学理论与模拟方法。 感兴趣的系统包括分子的大小从小到聚合物，状态从玻璃态到熔融态到（在适用的情况下）蒸气。设置范围从单组分到多组分系统，从支撑膜到层状膜，从溶液到共混物。 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、溶液和共混物。在薄膜的情况下，支持，独立的膜，和多层膜都将被调查。多种方法的使用将提供交叉检查不同策略的机会，以及将每种方法的结果与实验进行比较。这项研究将为不同环境中复杂系统的特性提供新的见解，并将产生工具，用于仅基于纯组分特性对混合物行为进行实质性预测。此外，在所述不同领域取得的进展将在它们重叠的领域创造机会。 示例包括：了解聚合物混合物从本体到薄膜的行为变化，研究超临界二氧化碳在离子液体中的溶解度，从这里描述的工作中，将为更大的科学界和更广泛的公众带来社会效益。新方法将扩大软物质社区的范围，使其能够应用所提出的工作成果。这一扩展的范围将得到计算工具的帮助，这些工具是为休闲科学用户编写的，并发布在小组网站上。 在人力资源方面，研究将为本科生、研究生和博士后研究员的参与创造持续的机会，特别是针对女本科生的努力。 这项工作将通过讲座、海报和出版物促进与科学公众联系的新机会，并向公众推广。

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