Ultrafast Vibrational Spectroscopy (2D-IR) of Carbon Dioxide in Ionic Liquid-Polymer Composite Materials

在这个由化学系化学结构、动力学和机理-A（CSDM-A）项目资助的项目中，匹兹堡大学的Sean Garrett-Roe教授的实验室正在使用激光研究如何使用新型材料来过滤掉发电厂释放的不需要的二氧化碳，在它到达大气之前。 这可能比目前的其他方法便宜得多。 例如，这些材料可以在塑料膜的结构内含有在室温下为液体的盐（离子液体）。 Garrett-Roe教授项目的目标之一是了解如何优化二氧化碳分子与新材料的相互作用。 该项目正在确定塑料膜内离子液体的结构，并利用这些信息来模拟控制二氧化碳如何通过材料的化学特征。 在研究的同时，该补助金还支持跨学科科学领域的研究生培训。 每年有两名来自历史悠久的黑人本科院校的本科生访问暑期研究机会。 此外，该项目还开发了教学基础设施，特别是一个在线平台，供教师开发，分享和获得新的POGIL（过程导向的引导探究学习）活动的反馈。该项目的具体目标是了解离子液体和交联聚乙二醇二丙烯酸酯（PEGDA）复合材料中的二氧化碳溶剂化。 该项目使用超快振动光谱（2D-IR）对二氧化碳的反对称拉伸来报告二氧化碳局部溶剂化环境的结构和动力学。 这项工作测试的假设，即二氧化碳的溶剂化环境是由离子液体的阴离子为主，聚合物基体减缓动力学通过增加活化熵重组溶剂壳。 假设的检验包括三个部分：（1）用一套工具，包括原子力显微镜、偏振光显微镜和扫描电子显微镜，覆盖从几十纳米到微米的长度尺度，确定离子液体- PEGDA离子凝胶中离子液体的结构;（2）通过记录作为离子液体体积百分比的函数的2D-IR光谱来测试溶剂化动力学的核-壳-基质模型;和（3）确定本体热力学和传输（溶解度、扩散率和渗透性）以及特定分子动力学（结构和旋转光谱扩散）的活化能。 该项目通过展示温度和偏振分辨方法来分离与振动发色团和周围溶剂的运动相关的活化能，从而推进2D-IR光谱。 该研究通过提供开发下一代材料所需的基本理解，支持了提高国家在全球高科技经济中竞争能力的重要目标。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

AbstractIn this project, funded by the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program of the Chemistry Division, Professor Sean Garrett-Roe’s laboratory at the University of Pittsburgh is using lasers to study how new types of materials could be used to filter out unwanted carbon dioxide that is given off by power plants, before it reaches the atmosphere. This could be much less expensive than other current methods. These materials could, for example, contain salts that are liquid at room temperature (ionic liquids) within the structure of plastic membranes. One of the aims of Professor Garrett-Roe’s project is to understand how to optimize the interactions of carbon dioxide molecules with the new materials. The project is determining the structures of the ionic liquids within the plastic membranes and using that information to model the chemical features that control how carbon dioxide moves through the materials. Parallel to the research, the grant supports the training of graduate students in interdisciplinary scientific areas. Two undergraduates per year from a historically black undergraduate institution visit for summer research opportunities. In addition, the project develops teaching infrastructure, specifically an online platform for teachers to develop, share, and get feedback on new POGIL (Process Oriented Guided Inquiry Learning) activities.The specific goal of this project is to understand carbon dioxide solvation in composites of ionic liquids and cross-linked poly(ethylene glycol) diacrylate (PEGDA). The project uses ultrafast vibrational spectroscopy (2D-IR) on the antisymmetric stretch of the carbon dioxide to report the structure and dynamics of carbon dioxide's local solvation environment. The work tests the hypothesis that the solvation environment of carbon dioxide is dominated by the anions of the ionic liquid, and that the polymer matrix slows dynamics by increasing the entropy of activation for reorganizing a solvent shell. The test of the hypothesis has three components: (1) to determine the structures of the ionic liquid in the ionic liquid - PEGDA ion gels with a suite of tools, including atomic force microscopy, polarized light microscopy, and scanning electron microscopy, covering length scales from tens of nanometers to microns; (2) to test a core-shell-matrix model of solvation dynamics by recording 2D-IR spectra as a function of ionic liquid volume percent; and (3) to determine the activation energies of bulk thermodynamics and transport (solubility, diffusivity, and permeability) as well as specific molecular dynamics (structural and rotational spectral diffusion). This project advances 2D-IR spectroscopy by demonstrating a temperature- and polarization-resolved approach to separate the activation energies related to motion of the vibrational chromophore and the surrounding solvent. The research supports important goals in advancing the nation's ability to compete in the global, high-technology economy by providing the fundamental understanding needed to develop next generation materials.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.