Multidimensional Methods for Kinetics in Complex Materials

在化学系化学测量和成像计划的支持下，南卡罗来纳大学的Mark Berg教授正在开发和应用基于激光的新方法，以测量聚合物和离子液体等复杂材料中的非常快速的化学反应。传统的方法使用激光脉冲来扰动化学体系一次，然后在一段时间内跟踪反应。该项目中开发的新方法将使用由精心选择的时间间隔分隔的多个扰动。这种方法应该允许观察复杂混合物中特定类型的分子或反应，例如光激发分子在光活性材料中的碰撞。这个项目将扩大这些方法可以应用的过程和时间尺度，从而允许它们应用于更广泛的问题。具体目标包括：当分子聚合时，均相的小分子溶剂如何变得多相？离子液体中会出现不同分子大小的位置吗？这些位置是否会改变以离子液体为溶剂的反应的进程？光激发在共轭聚合物中的传播距离是多少？由此产生的碰撞如何熄灭俘获的能量？伯格教授积极参与了一项大学范围内的倡议，增加代表人数不足的群体申请研究生院的人数。他还参加了一个由NSF资助的IGERT项目，该项目旨在南卡罗来纳大学发展跨学科培训项目。

With support from the Chemical Measurement and Imaging program in the Division of Chemistry, Professor Mark Berg of the University of South Carolina is developing and applying new laser based methods for measuring very fast chemical reactions in complex materials such as polymers and ionic liquids. Traditional methods use a laser pulse to perturb a chemical system once and then follow the reaction over a single time period. The new methods developed in this project will use multiple perturbations separated by carefully chosen time intervals. This approach should allow for the observation of specific types of molecules or reactions within a complex mixture, for example the collisions of light-excited molecules in photoactive materials.This project will expand the range of processes and time scales where these methods can be applied and thereby allow their application to a wider range of problems. Specific targets include: How does a homogeneous, small-molecule solvent become heterogeneous as the molecule polymerizes? Do different molecule-sized sites occur in an ionic liquid, and do these sites alter the progress of reactions that use ionic liquids as the solvent? What is the range of travel for an optical excitation in a conjugated polymer, and how do the resulting collisions quench captured energy? Professor Berg is active in a university-wide initiative to increase applications to graduate school by underrepresented groups. He is also participating in an NSF-funded IGERT program aimed at developing interdisciplinary training programs at the University of South Carolina.