Ideal Probe Single Molecule Imaging for the Study of Small Molecule and Polymeric Glass Formers

在这个由化学系化学结构动力学和机制（CSDM-A）项目资助的项目中，哥伦比亚大学的劳拉考夫曼教授正在使用先进的成像技术来研究分子如何在一类被称为玻璃成型剂的材料中移动。玻璃形成物可能以过冷液体或玻璃的形式存在，这些材料在微观和宏观尺度上都表现出不寻常和知之甚少的行为。这些材料在自然界和现代技术中无处不在，存在于窗户玻璃，塑料和以药丸和片剂形式提供的药物中。了解分子如何在这些系统中移动不仅解决了基本问题，而且还增强了对如何稳定这些材料以防止各种类型降解的理解。PI开发并使用单分子成像方法来详细描述这些系统中分子的旋转和平移，梳理出与这些环境中分子运动和弛豫相关的关键时间尺度和长度尺度。在过冷液体中进行的单分子成像实验采用了新设计和合成的理想探针分子;这些探针在玻璃宿主中的非均匀性在空间或时间上不平均。因此，这些探针直接询问这些系统中感兴趣的长度和时间尺度，并测试玻璃化转变理论的预测。实验详细的动态异质性，表现在小分子和聚合物玻璃形成的旋转动力学的弛豫和交换时间分布。此外，需要子衍射本地化的实验正在进行以下平移动力学和结构重排过冷液体，以解决有关的旋转平移解耦现象知之甚少的问题。采用两种类型的探针的相关技术来测量动态相关性，允许识别的长度尺度的过冷液体中的异质性。理想的探针单分子测量也在薄聚合物膜中进行，重点是识别对薄膜器件和气相沉积玻璃的稳定性具有实际影响的假定表面移动的层。为了补充通过冷却制备的玻璃态系统的研究，也正在进行通过溶胀制备的此类系统的研究。这些研究都详细的动态异质性方面，并直接可视化这些系统中的长时间尺度弛豫的结构重排。

In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Laura Kaufman of Columbia University is using advanced imaging techniques to study how molecules move in a class of materials known as glass formers. Glass formers may exist as supercooled liquids or glasses, materials that demonstrate unusual and poorly understood behaviors at both the microscopic and macroscopic scales. These materials are ubiquitous in nature and in modern technology, present in window glass, plastics, and medications delivered as pills and tablets. Understanding how molecules move in these systems not only addresses fundamental questions but also enhances understanding of how to stabilize these materials against various types of degradation. The PI develops and uses single molecule imaging approaches to detail the rotations and translations of molecules in these systems, teasing out key time scales and length scales related to molecular motions and relaxations in these environments. The single molecule imaging experiments in supercooled liquids underway employ newly designed and synthesized ideal probe molecules; these are probes that do not average in space or time over heterogeneities in a glassy host. As a result, these probes directly interrogate length and time scales of interest in these systems and test predictions of theories of the glass transition. The experiments detail dynamic heterogeneity as manifested in relaxation and exchange time distributions of rotational dynamics in both small molecule and polymeric glass formers. In addition, experiments that require sub-diffraction localization are being performed to follow translational dynamics and structural rearrangements in supercooled liquids to resolve questions regarding the poorly understood phenomenon of rotational-translational decoupling. Related techniques employing two types of probes are employed to measure dynamic correlations, allowing identification of length scales of heterogeneity in supercooled liquids. Ideal probe single molecule measurements are also being performed in thin polymeric films, with a focus on identifying the putative surface mobile layer that has practical ramifications for the stability of thin film devices and vapor-deposited glasses. To complement studies of glassy systems prepared through cooling, studies of such systems prepared through swelling are also underway. These studies both detail aspects of dynamic heterogeneity and directly visualize structural rearrangements underlying long time scale relaxations in these systems.