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Thermodynamic and Dynamic Behaviour in Polymer Melts, Glasses, and Mixtures: Links to Structure Using Theory and Simulation

聚合物熔体、玻璃和混合物的热力学和动态行为：使用理论和模拟与结构的联系

基本信息

批准号：
1708542
负责人：
Jane Lipson
金额：
$ 33万
依托单位：
Dartmouth College
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-12-01 至 2021-01-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1708542&HistoricalAwards=false
关键词：
Thermodynamic Dynamic Behaviour Polymer Melts

项目摘要

NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education on polymeric systems and related materials. There are many applications for synthetic materials such as polymers, ranging from coatings for electronics, to clothing, furniture, and airplane components. Ideally, the material properties will be well matched to the intended use: e.g. tough and abrasion-resistant for hard-shell suitcases, resistant to tear for garbage bags. New synthetic strategies are yielding impressive ability to design a large molecule down to the level of which atoms are incorporated and how they are locally connected. In this project, the PI and her group will use theory and simulation to develop new tools for predicting how molecular composition controls bulk material properties. Because so many applications involve thin films, the effects of interfaces will also be of strong interest. One of the important themes that runs through much of the proposed research involves the "unused" volume captured within a solid or liquid; this will change with pressure and temperature. For example, a liquid will become more dense as temperature is lowered; a solid glassy state has less "free" volume than the liquid. Prior research in the PI's group shows that theoretical predictions for free volume correlate with materials properties, e.g. its melting temperature, how it absorbs energy, and its tendency to mix. This work will focus on linking free volume and molecular structure. The aim is to complete the path connecting the microscopic design of large molecules to their bulk and film properties. The process will introduce new strategies to the scientific community for materials design. Education and training of all undergraduate students and postdocs involved in the research will be broad since a strong emphasis in the PI's research is to hold simulation and theory directly accountable to experimental results. The PI has a strong track record of involving women in research, and also maintains an interest in public outreach.TECHNICAL SUMMARYThis award supports theoretical research and education aimed at discovering links between structure, equilibrium properties, and dynamic response in polymer melts, mixtures and glasses, in the bulk and confined through interfaces. Synthesis experts are developing methods that allow for increasing control of molecular content, and the ability to draw bright lines between chemical constituency and behavior is crucial. Materials of interest here include macromolecules in melt and solution, and glassy solids. Both analytic theory as well as simulations will be brought to bear, and the two routes will overlap for some of the studies of interest. The research will generate testable predictions that will be held accountable to experimental data. The result will be new strategies for choosing molecular constituents so as to produce desired physical properties. The goals of research include: (1) Connections between thermodynamic characterization and dynamic response. Preliminary evidence shows that the Locally Correlated Lattice (LCL) model developed under prior NSF support yields a well-defined thermodynamic quantification of free volume. Further, the free volume predictions correlate with the glass transition, and suggest an explanation for the temperature and volume dependence of dynamic relaxation in polymeric and small molecule systems. The PI aims to extend these results to a large variety of polymeric and other glassy systems, using relaxation data that spans many decades, as well as a broad range of temperatures and pressures. Thermodynamic scaling using the LCL free volume will collapse the entire data set for each system to a single line, requiring only a single optimization parameter. Application to many systems will allow correlation between local chemical structure, which can be synthetically controlled, and the material dependent scaling parameter. The result will be an ability to predict how a designed structure will dynamically relax. The scaling analysis will also lead to predictions about the pressure dependence of dynamic relaxation, given only ambient pressure experimental data. Both bulk and thin film systems will be studied.(2) Free Volume and Cohesive Energy Density as Orthogonal Controls on Miscibility. The cohesive energy density has a poor history of predicting miscibility in polymer solutions and blends. Application of the LCL model to study mixing behavior has shown the LCL free volume to be an orthogonal metric to cohesive energy density; there is evidence that it can serve as a predictive tool where the cohesive energy density fails. The LCL theory can predict both quantities, which will allow this hypothesis to be tested. Application to many systems will allow correlations with molecular properties, a particular interest being chain stiffness. (3) A Coarse-grained Simulation Method for Studying the Effects of Interfaces. Introduction and control of interfaces plays an increasingly important role in material design. The PI's Limited Mobility simulation approach can model a range of experimentally observed behavior. Key features include decoupling between local density and local mobility, and incorporating nearest-neighbor facilitation for local moves. Initial results indicate that simulation parameter values connect closely with experimentally measured characteristic molecular properties. In this work, the limited mobility model will be applied to capture the disruptive influences of a wide variety of interfaces, including anti/plasticizing additives and multilayer systems.

该奖项支持聚合物系统和相关材料的理论和计算研究和教育。聚合物等合成材料有许多应用，从电子涂料到服装、家具和飞机部件。理想情况下，材料性能将与预期用途：匹配良好：例如，坚韧且耐磨的硬壳行李箱，耐撕裂的垃圾袋。新的合成策略正在产生令人印象深刻的能力，可以设计一个大分子，直到原子被合并以及它们如何局部连接的水平。在这个项目中，PI和她的团队将使用理论和模拟来开发新的工具，用于预测分子组成如何控制散装材料的性能。由于如此多的应用涉及薄膜，界面的影响也将是强烈的兴趣。贯穿许多拟议研究的重要主题之一涉及固体或液体中捕获的“未使用”体积;这将随着压力和温度而变化。例如，当温度降低时，液体会变得更致密;固体玻璃态的“自由”体积比液体小。 PI小组先前的研究表明，自由体积的理论预测与材料特性相关，例如其熔化温度，吸收能量的方式以及混合的趋势。这项工作将集中在连接自由体积和分子结构。其目的是完成连接大分子的微观设计与其体积和薄膜性质的路径。这一过程将为材料设计的科学界引入新的策略。参与研究的所有本科生和博士后的教育和培训将是广泛的，因为PI研究的重点是让模拟和理论直接对实验结果负责。该奖项支持旨在发现聚合物熔体、混合物和玻璃中的结构、平衡性质和动态响应之间的联系的理论研究和教育，无论是在散装还是通过界面限制。合成专家正在开发允许增加对分子含量的控制的方法，并且在化学成分和行为之间画出清晰界限的能力至关重要。这里感兴趣的材料包括熔体和溶液中的大分子，以及玻璃状固体。分析理论和模拟都将发挥作用，这两条路线将在一些感兴趣的研究中重叠。这项研究将产生可测试的预测，这些预测将对实验数据负责。其结果将是选择分子成分的新策略，以产生所需的物理性质。研究的目标包括：（1）热力学特性和动态响应之间的联系。初步证据表明，在先前NSF支持下开发的局部相关晶格（LCL）模型产生了定义明确的自由体积的热力学量化。此外，自由体积的预测与玻璃化转变，并建议在聚合物和小分子系统的动态松弛的温度和体积依赖性的解释。PI的目的是将这些结果扩展到各种各样的聚合物和其他玻璃体系，使用跨越几十年的弛豫数据，以及广泛的温度和压力。使用LCL自由体积的热力学缩放将每个系统的整个数据集压缩到单条线，仅需要单个优化参数。许多系统的应用程序将允许本地化学结构，这可以综合控制，和材料相关的缩放参数之间的相关性。其结果将是预测设计结构如何动态松弛的能力。标度分析也将导致预测的压力依赖性的动态松弛，仅给定环境压力的实验数据。体和薄膜系统将被研究。(2)自由体积和内聚能密度对混溶性的正交控制。内聚能密度在预测聚合物溶液和共混物的相容性方面的历史不佳。应用LCL模型研究混合行为表明，LCL自由体积是内聚能密度的正交度量;有证据表明，它可以作为内聚能密度失效的预测工具。LCL理论可以预测这两个量，这将允许这个假设被测试。应用于许多系统将允许与分子性质的相关性，特别感兴趣的是链刚度。(3)研究界面效应的粗粒度模拟方法。界面的引入和控制在材料设计中起着越来越重要的作用。PI的有限移动性模拟方法可以模拟一系列实验观察到的行为。主要特点包括本地密度和本地流动性之间的脱钩，并纳入最近的邻居促进本地移动。初步结果表明，模拟参数值与实验测量的特征分子性质密切相关。在这项工作中，有限的流动性模型将被应用到捕捉各种各样的接口，包括抗/增塑添加剂和多层系统的破坏性影响。