Elucidating Length and Time Scales of Spatiotemporal Heterogeneity in Supercooled Liquids

在这个由化学系化学结构、动力学和机制计划支持的项目中，劳拉·考夫曼教授将与她的博士后同事、研究生和哥伦比亚大学的本科生研究人员一起，研究小分子和模拟过冷液体中时空不均一性的基本方面。拟议的实验将采用一套精心挑选的探测分子，允许系统地询问各种小分子玻璃成型器中异质性的长度和时间尺度。这些测量将详细说明非均质性的空间和时间范围，特别是过冷液体，并可能表明过冷液体的脆性与时空不均一性的广度之间的潜在联系。除了典型的过冷液体外，还提出了对表现出类似现象但被怀疑具有结构非均质性的系统的实验。除了监测单分子(SM)探测器旋转动力学的这些测量之外，还将进行直接询问SM水平上的平移扩散的实验。同时跟踪旋转和平移将解决关于过冷液体中旋转-平移去耦合现象的鲜为人知的问题，揭示这种行为是否可以存在于单分子水平上。伴随着精心设计的模拟，将允许以与拟议的实验类似的方式跟踪旋转和平移运动性，并将以一种将告知并加强对实验结果的解释的方式来研究探测器与宿主的相互作用。更全面地了解过冷液体中的时空非均质性，在从石油运输到细胞低温保存的各个领域都具有重要的基础意义和应用价值。这项拟议的工作也将对考夫曼实验室的本科生、研究生和博士后研究人员以及年轻学生产生强烈的教育影响。考夫曼教授与当地一所特许学校建立了合作关系，向4-6年级的学生讲授复杂流体的课程，与他们的科学老师合作开发额外的课程，并将该学校使用的实时评估工具转化为哥伦比亚大学的普通化学课程。通过在哥伦比亚大学生活质量委员会的服务，考夫曼教授将促进向哥伦比亚大学理科学生和教职员工传播有关联邦机构和以大学为基础的家庭友好政策的信息，并将协助设计、传播和分析一项关于哥伦比亚大学教职员工使用情况和对大学家庭假政策的看法的研究。

In this project supported by the Chemical Structure, Dynamics and Mechanisms Program of the Division of Chemistry, Professor Laura Kaufman, together with her postdoctoral associates, graduate students, and undergraduate researchers at Columbia University will investigate fundamental aspects of spatiotemporal heterogeneity in small molecule and simulated model supercooled liquids. The proposed experiments will employ a set of carefully chosen probe molecules that allow for systematic interrogation of the length and time scales of heterogeneity in a variety of small molecule glass formers. These measurements will detail the spatial and temporal extents of heterogeneity in particular supercooled liquids and may suggest underlying connections between supercooled liquid fragility and breadth of spatiotemporal heterogeneity. Beyond typical supercooled liquids, experiments on systems that display similar phenomenology but are suspected of possessing structural heterogeneity are proposed. In addition to these measurements that monitor single molecule (SM) probe rotational dynamics, experiments that directly interrogate translational diffusion at the SM level will be undertaken. Simultaneous tracking of rotations and translations will resolve questions regarding the poorly understood phenomenon of rotational-translational decoupling in supercooled liquids, revealing whether this behavior can exist on a single molecule level. Accompanying carefully crafted simulations will allow for both rotational and translational motility to be tracked in analogy with the proposed experiments and will investigate reciprocal probe-host interactions in a manner that will inform and strengthen interpretation of experimental results. Achieving a fuller understanding of spatiotemporal heterogeneity in supercooled liquids is of great fundamental interest as well as of applied interest in diverse fields, from petroleum transportation to cryopreservation of cells. The proposed work will also have strong educational impact on undergraduate, graduate, and postdoctoral researchers in the Kaufman laboratory as well as on younger students. Professor Kaufman has initiated a relationship with a local charter school to present lectures on complex fluids to 4th-6th grade students, collaboratively develop additional lectures with their science teacher, and translate real-time assessment tools used in this school into the General Chemistry courses at Columbia University. Through service on Columbia University's Quality of Life Committee, Professor Kaufman will facilitate dissemination of information to Columbia University science students and faculty on federal agency and University-based family friendly policies, and will assist in design, dissemination, and analysis of a study on Columbia University faculty use and perceptions of the University's family leave policies.