Single Molecule Imaging for the Study of Heterogeneous Materials: Supercooled Liquids, Polymer Nanocomposites, and Ionic Liquids

用于研究异质材料的单分子成像：过冷液体、聚合物纳米复合材料和离子液体

基本信息

批准号：
1954803
负责人：
Laura Kaufman
金额：
$ 48万
依托单位：
Columbia University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-06-01 至 2023-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1954803&HistoricalAwards=false
关键词：
Single Molecule Imaging Study Heterogeneous

项目摘要

We may think of a container of a pure liquid as uniform, the same properties (for example, density, refractive index and viscosity) throughout the sample container. At the molecular level however, the liquid is not uniform, but highly varied in how the molecules are arranged with respect to one another. At most temperatures, molecules are in motion. At any given moment, some regions of the liquid might be denser, or more viscous than other regions. This condition is called “dynamic heterogeneity,” and it is an important consideration in discussing the mechanical properties of polymers, how proteins move through water, etc. Dynamic heterogeneity is difficult to measure precisely - most measurements look at averages within a sample. In this project, funded by the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program of the Chemistry Division, Professor Laura Kaufman of Columbia University and her students are using an advanced molecular imaging technique that can track the motion of a single (molecule probe) through a liquid or polymer material. The probe molecule is strongly fluorescent, meaning that when exposed to light of one wavelength, it emits light of another specific wavelength. The emitted light allows the molecule to be tracked as it moves through different regions of the material. The probe reveals dynamic heterogeneity as its motions are altered by changes in the structure of its environment. Professor Kaufman and her students are investigating dynamic heterogeneity in supercooled liquids (liquids colder than their freezing temperature but somehow still liquid), polymer nanocomposites (used in gas separations and electronic components), and ionic liquids. Most familiar ionic systems are solid, like table salt. Ionic liquids are composed of positive and negative ions but are liquid at room temperature. Ionic liquids may have potential for “green” industrial processes. The students engaged in this research are learning a broad range of experimental techniques and analysis approaches relevant to the specific project, These approaches are also applicable to many areas of science and emerging technologies. In addition to providing training for graduate students, this project also includes outreach to K-8 students. The outreach events feature topics that provide an entry point to chemistry concepts such as phase diagrams and the concept of chemical stability.Professor Kaufman and her students are refining and extending single molecule imaging approaches to detail aspects of dynamic heterogeneity in small molecule supercooled liquids and polymeric glass formers, with advances coming in the form of new probe molecules and new techniques to distinguish spatial and temporal heterogeneity. At the same time, the scope of this work is being extended to polymer nanocomposites and ionic liquids. Newly designed tethered probe molecules are prepared and used to complement free probe measurements and discriminate changes in dynamics that occur due to environmental rearrangement from those related to probe translocation. The tethered probes provide a new approach to characterizing spatial extent of regions of distinct dynamics in these complex systems. The project also employs super-resolution experiments that allow simultaneous tracking of rotations and translations; this study seeks to resolve questions regarding the poorly understood phenomenon of rotational-translational decoupling, clarifying if it emerges from experimental biasing. The study of polymer nanocomposites focuses on the dynamics of the interfacial layer, and how interfacial layer properties vary with changes in the host matrix. Molecular probes are being developed to clarify how the interaction between structural and dynamic heterogeneity influences the properties of ionic liquids.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.

我们可以认为纯液体的容器是均匀的，整个样品容器具有相同的属性（例如，密度、折射率和粘度），但是在分子水平上，液体并不均匀，而是在如何变化方面存在很大差异。在大多数温度下，分子都处于运动状态，液体的某些区域可能比其他区域更稠密或更粘稠，这种情况称为“动态异质性”。是讨论中的一个重要考虑因素动态异质性很难精确测量 - 大多数测量都着眼于样品内的平均值，该项目由化学结构、动力学和机制-A (CSDM-) 资助。 A）化学系的项目，哥伦比亚大学的劳拉·考夫曼教授和她的学生正在使用一种先进的分子成像技术，可以跟踪单个（分子探针）穿过液体或聚合物材料的运动，这意味着探针分子是荧光的。那当暴露于一种波长的光时，它会发射另一种特定波长的光，当分子穿过材料的不同区域时，探针可以通过其结构的变化来跟踪分子的动态异质性。考夫曼教授和她的学生正在研究过冷液体（比冰点温度低但仍然是液体的液体）、聚合物纳米复合材料（用于气体分离和电子元件）和离子的动态异质性。大多数熟悉的离子系统都是固体，例如食盐，离子液体由正离子和负离子组成，但在室温下离子液体可能具有“绿色”工业过程的潜力。与特定项目相关的广泛的实验技术和分析方法，这些方法也适用于许多科学领域和新兴技术，除了为研究生提供培训外，该项目还包括向 K-8 学生进行推广活动。提供化学概念切入点的主题例如相图和化学稳定性的概念。考夫曼教授和她的学生正在完善和扩展单分子成像方法，以了解小分子过冷液体和聚合物玻璃形成体中动态异质性的细节，并以新探针分子的形式取得进展同时，这项工作的范围正在扩展到聚合物纳米复合材料和离子液体的制备和补充。自由探针测量并区分由于环境重排而发生的动态变化与探针易位相关的动态变化，该项目还采用了超分辨率实验来表征这些复杂系统中不同动态区域的空间范围。允许同时跟踪旋转和平移；这项研究旨在解决人们对旋转平移解耦现象知之甚少的问题，澄清它是否是由实验偏差产生的。界面层，以及界面层性质如何随着主体基质的变化而变化。正在开发分子探针，以阐明结构异质性和动态异质性之间的相互作用如何影响离子液体的性质。该奖项反映了 NSF 的法定使命，并被认为是值得的。通过使用基金会的智力优势和更广泛的影响审查标准进行评估来获得支持。