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Connecting Dynamics and Thermodynamics to Predict Mobility and Glassiness

连接动力学和热力学来预测流动性和玻璃度

基本信息

批准号：
2006504
负责人：
Jane Lipson
金额：
$ 35万
依托单位：
Dartmouth College
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-12-01 至 2024-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2006504&HistoricalAwards=false
关键词：
Connecting Dynamics Thermodynamics Predict Mobility

项目摘要

Non-technical abstractThis research will lead to new understanding of how certain very widely-used materials behave and why they sometimes misbehave. Some solid materials are crystalline; table salt and sugar are two familiar examples. In these cases the atoms or molecules that make up the solid are regularly positioned and highly organized, and their structure and properties do not change with time - they are at equilibrium. In many other cases the solids are glassy, as if the particles in the liquid state were stuck in place. Window glass is just one example; it is made of small molecules containing silicon and oxygen. A large fraction of specially designed materials, which often involve very large molecules known as polymers, are also in the glassy solid state. Although glassy solids have been part of our surroundings for centuries, there are still aspects of their behavior that are not well understood. Examples from daily life include protective coatings, photoresists, polymers reinforced with nanoparticles, membranes, and filters. In each of these cases a significant fraction of the glassy solid molecules are near an interface; different kinds of experiments have led to the conclusion that these molecules can behave very differently from neighboring molecules ensconced in the bulk. A related problem is that, where glassy solid properties are carefully designed to optimize performance, as the material ages its properties can change in undesirable ways. These situations reflect the fact that glassy solids, unlike crystalline solids, are not at equilibrium; and their properties can shift over time. These changes can affect their performance, and therefore cause problems. This project will produce new ways of modeling glassy solids that will account for the influence of a neighboring surface on how molecules pack. The models will work together with experimental data and lead to new methods for understanding and predicting the ways that glassy material behavior can change when interfaces are present.Technical abstractDynamic relaxation of material begins locally through segmental motion; its progression over short time and length scales drives the longer and larger response. Dynamic behavior also reflects the local structural and energetic characteristics that determine thermodynamic properties. The research proposed here will reveal deep connections between these realms by using and advancing thermodynamic (Locally Correlated Lattice) and dynamic (Cooperative Free Volume) models originated in the PI's research group. This new set of tools will be applied to predict glassy material behavior over a wide range of conditions. Two areas of particular focus involve the presence of interfacial regions and the effect of different experimental pathways used to mimic the effects of long-time aging. This research involves interrelated projects:(a) A model will be developed for the interfacial region from very near (nm) the surface to distances where bulk behavior is recovered. It will lead to predictions for local density, mobility (mobile layer thickness), segmental relaxation times, and the changing lengthscale of cooperative motion, as functions of distance from the interface, temperature, and film thickness.(b) A new model will be introduced for nanocomposites that reflects differences between the interfacial region (next to the particles) and the matrix. This model, informed by thermodynamic properties, will lead to predictions for segmental dynamics and changes in cooperative length scales as functions of temperature, pressure, and nanoparticle loading.(c) Advances from (a) and (b) will lead to new ways for connecting the thermodynamic and dynamic properties of glass formers to their long term stability. This work will also lead to insight about how those connections depend on the experimental path to glassiness.The materials targeted by this project serve an extremely wide range of functions, and this research will lead to new insight about how their molecular nature links to the particular properties that make them uniquely suited to their applications. The new models resulting from this research will be accessible and generally useful for linking thermodynamic properties to dynamic behavior.The PI will further successful efforts to involve and encourage STEM participation among women and will continue working with graduate and undergraduate students to add new resources on polymer-related science to the public knowledge base. The PI will also continue energetic efforts to introduce fundamental concepts in physical science to the general public.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要这项研究将导致对某些非常广泛使用的材料的行为以及为什么它们有时会出现错误的新理解。有些固体物质是晶体，食盐和糖就是两个常见的例子。在这些情况下，组成固体的原子或分子是规则定位和高度组织的，它们的结构和性质不随时间而变化-它们处于平衡状态。在许多其他情况下，固体是玻璃状的，好像液态的颗粒被粘在原地。窗玻璃只是一个例子;它是由含有硅和氧的小分子制成的。大部分特殊设计的材料，通常涉及非常大的分子，称为聚合物，也处于玻璃态。虽然玻璃状固体已经存在了几个世纪，但它们的行为仍有一些方面没有得到很好的理解。日常生活中的例子包括保护涂层、光致抗蚀剂、用纳米颗粒增强的聚合物、膜和过滤器。在每一种情况下，都有相当一部分的玻璃态固体分子靠近界面;不同种类的实验得出这样的结论：这些分子的行为可能与位于本体中的相邻分子非常不同。一个相关的问题是，在玻璃态固体性质被仔细设计以优化性能的情况下，随着材料老化，其性质可能以不期望的方式改变。这些情况反映了这样一个事实，即玻璃态固体与结晶态固体不同，它们并不处于平衡状态;它们的性质会随着时间的推移而变化。这些变化可能会影响其性能，从而导致问题。这个项目将产生新的方法来模拟玻璃状固体，将考虑到相邻表面对分子如何堆积的影响。该模型将与实验数据一起工作，并导致新的方法来理解和预测的方式，玻璃质材料的行为可以改变时，接口present.Technical abstractDynamic松弛的材料开始局部通过分段运动，其进展在短时间和长度尺度驱动器的更长和更大的响应。动力学行为也反映了决定热力学性质的局部结构和能量特征。这里提出的研究将通过使用和推进起源于PI研究小组的热力学（局部相关晶格）和动力学（合作自由体积）模型来揭示这些领域之间的深层联系。这套新的工具将被应用于预测玻璃材料在各种条件下的行为。特别关注的两个领域涉及界面区域的存在和用于模拟长期老化效应的不同实验途径的影响。这项研究涉及相关的项目：（a）将开发一个模型的界面区域从非常接近（nm）的表面的距离，在那里批量行为恢复。它将导致预测局部密度，流动性（移动的层厚度），节段弛豫时间，和合作运动的变化的长度尺度，作为从界面的距离，温度和膜厚度的函数。(b)一个新的模型将被引入纳米复合材料，反映界面区域（旁边的颗粒）和基体之间的差异。该模型，通知的热力学性质，将导致预测的节段动力学和合作的长度尺度的变化作为温度，压力和纳米粒子负载的函数。(c)（a）和（B）的进展将导致将玻璃形成物的热力学和动力学性质与其长期稳定性联系起来的新方法。这项工作也将导致洞察这些连接如何依赖于实验路径的玻璃化。该项目的目标材料具有非常广泛的功能，这项研究将导致新的见解，了解它们的分子性质如何与使它们独特适合其应用的特定属性联系起来。从这项研究中产生的新模型将是可访问的，通常用于将热力学性质与动态行为联系起来。PI将进一步成功地努力吸引和鼓励女性参与STEM，并将继续与研究生和本科生合作，为公共知识库增加聚合物相关科学的新资源。PI还将继续积极努力向公众介绍物理科学的基本概念。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。