Collaborative Research: Molecular-level Understanding of Small Molecule Transport in Glassy Polymers exhibiting Configurational Free Volume

近年来开发了许多新的膜材料，但很少有工业应用，主要是由于在实际操作条件下缺乏耐久性和坚固性。这一研究项目旨在从分子水平上了解膜材料中的传输机制，并为下一代膜材料的发展提供信息，这些材料可以与传统的能源密集型气体分离技术竞争。将要研究的膜材料的类型具有在材料中产生永久的、不可折叠的空隙(自由体积)的分子结构。与目前的分离膜不同，自由体积可用于选择性气体吸附，而空隙周围的分子结构有助于材料保持其自由体积和分离性能。这项研究产生的科学知识应该能够使分离膜取得重大进展，满足广泛的工业应用的需要。该研究项目作为本科生和研究生进行尖端研究的培训基地，将吸引在STEM领域代表性不足的群体的学生。研究人员还将参与结构良好的教育和外联活动，包括开发新课程，为高中生制定教育和研究内容，在公共“研究之夜”活动上发表演讲，以及为普通公众创建教育视频流。本研究项目的目的是阐明基于构象和构型的自由体积如何单独和协同地对膜的传输特性做出贡献。研究假设是，构象自由体积比构象自由体积更稳定，因此即使在恶劣的条件下，即在高温和具有化学挑战性的环境中，它也提供了前所未有的抗物理老化和塑化的能力。我们将合成具有特定的、但系统的、不同自由体积结构的聚丁二烯聚合物，并研究构型自由体积对分子传输的影响。基本输运性质(即吸附、扩散和渗透)将在环境和恶劣条件下进行实验和理论研究。最后，原子模拟将被用来阐明基于构型自由体积的聚合物中的基本输运机制以及纳米限制的影响。该项目的成果将是改进的工业气体分离膜，特别是在恶劣的条件下。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Many new membrane materials have been developed in recent years; however, very few of them have made it to industrial applications, mainly due to lack of durability and robustness under realistic operating conditions. This research project aims to develop a molecular-level understanding of transport mechanisms in membrane materials and to inform the development of the next generation of membrane materials that can compete with traditional energy-intensive gas separations technologies. The types of membrane materials that will be investigated have a molecular structure that creates permanent, non-collapsible voids (free volume) in the material. The free volume is available for selective gas sorption, and the molecular structure around the voids helps the material to maintain its free volume and separation performance, unlike current separation membranes. The scientific knowledge generated by this research should enable significant advances in separation membranes that will meet the needs for a broad range of industrial applications. The research project serves as a training ground for undergraduate and graduate students to perform cutting edge research and will engage students from groups underrepresented in STEM fields. The researchers will also engage in well-structured education and outreach activities, including developing new courses, formulating educational and research components for high school students, giving presentations at a public "research night" event, and creating an educational video streaming for general public. The goal of this research project is to elucidate how conformation- and configuration-based free volume contribute, individually and synergistically, to the membrane transport properties. The research hypothesis is that configurational free volume is much more stable than conformational free volume, and thus it provides unprecedented resistance to physical aging and plasticization even under harsh conditions, i.e., at high temperature and in chemically challenging environments. Iptycene-based polymers with specifically, yet systematically, varied free volume architecture will be synthesized, and the effect of configurational free volume on molecular transport will be studied. Fundamental transport properties (i.e., sorption, diffusion and permeation) will be investigated experimentally and theoretically under both ambient and harsh conditions. Finally, atomistic simulations will be performed to elucidate the underlying transport mechanism in polymers with configuration-based free volume and the effect of nano-confinement. The outcome of this project will be improved membranes for industrial gas separations, especially under harsh conditions.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.