Single Molecule Studies for Characterizing Dynamical and Mechanical Properties of Glassy Systems

哥伦比亚大学的Laura考夫曼教授在化学系化学结构、动力学和机制A（CSDM-A）项目的支持下，正在使用单分子显微镜方法研究玻璃状聚合物中的结构域。玻璃似乎是固体，但与晶体相反，它们具有更类似于液体的无定形结构。聚合物，如塑料和橡胶，经常形成玻璃状固体。虽然它们在现代生活中无处不在，但它们仍然表现出人们知之甚少的行为。例如，它们似乎是由小的结构域组成的，这些结构域缓慢地穿过看似固体的材料，通常以不同的速度移动。考夫曼教授和她的学生们正在观察嵌入聚合物中的单个分子的荧光，以跟踪这些结构域的运动。他们的发现可以为材料的设计提供信息，这些材料可用于从家用物品到太阳能电池和生物医学材料的广泛应用。从事这项研究的学生学习广泛的实验技术和分析方法，适用于许多科学和技术领域。考夫曼小组还定期与K-12学生通过讲座和演示，向学生介绍玻璃材料的异常有趣的特性。教授考夫曼将完善和扩展单分子成像。补充方法的增加，预计将提供一个更详细的动态异质性聚合物玻璃形成。从新型探针检测到的荧光信号将在几分钟到几小时的时间尺度上进行跟踪，并用于表征玻璃态聚苯乙烯中异质区域的长度尺度、组织和机械性能。首先，一组实验比较自由和拴系的单分子探针在物理缠结和化学交联的聚合物的行为将阐明方面的空间范围的异质域。在此之后，调查在聚苯乙烯的玻璃化转变温度以下，包括以下扰动的散装和本地的机械性能，将在这个和类似的系统。考夫曼团队将使用模块化方法进行综合成像和流变学实验，以详细说明玻璃中的体相机械性能、局部自由体积和时空局部动力学之间的联系。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program in the Division of Chemistry, Professor Laura Kaufman of Columbia University is using single-molecule microscopy methods to study structural domains in glassy polymers. Glasses appear to be solid, but in contrast to crystals, they have amorphous structures that are more akin to liquids. Polymers, like plastics and rubbers, frequently form glassy solids. While they are ubiquitous in modern life, they still exhibit poorly understood behaviors. For example, they appear to be made up of small structural domains that slowly move through the seemingly solid material, oftentimes at different speeds. Professor Kaufmann and her students are watching the fluorescence from individual molecules embedded within polymers to track the movement of these domains. Their discoveries could inform the design of materials for use in a wide range of applications, from household goods to solar cells and biomedical materials. The students engaged in this research learn a broad range of experimental techniques and analysis approaches that are applicable to many areas of science and technology. The Kaufman group also regularly engages with K-12 students through talks and demonstrations that introduce students to the unusually interesting properties of glassy materials. Professor Kaufman will refine and extend single molecule imaging. The addition of complementary approaches is expected to provide for a more detailed view of dynamic heterogeneity in polymeric glass formers. Fluorescence signals detected from novel probes will be followed over time scales ranging from minutes to hours and used to characterize the length scale, organization, and mechanical properties of heterogeneous regions in glassy polystyrene. First, a set of experiments comparing the behavior of free and tethered single molecule probes in physically entangled and chemically cross-linked polymers will elucidate aspects of the spatial extent of heterogeneous domains. Following this, investigations into bulk and local mechanical properties in polystyrene below its glass transition temperature, including following perturbations, will be undertaken in this and similar systems. Using a modular approach, the Kaufman group will perform integrated imaging and rheology experiments to detail connections between bulk mechanical properties, local free volume, and spatiotemporally local dynamics in glasses.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.