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型膜材料；然而，由于在实际操作条件下缺乏耐用性和坚固性，它们很少能够应用于工业应用。该研究项目旨在从分子水平上理解膜材料的传输机制，并为下一代膜材料的开发提供信息，这些膜材料可以与传统的能源密集型气体分离技术竞争。将被研究的膜材料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。自由体积可用于选择性气体吸附，与目前的分离膜不同，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将使分离膜取得重大进展，满足广泛工业应用的需要。该研究项目将作为本科生和研究生进行前沿研究的培训基地，并将吸引来自STEM领域中代表性不足的群体的学生。研究人员还将参与组织良好的教育和推广活动，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，以及为公众创建教育视频流。本研究项目的目标是阐明基于构象和构型的自由体积如何单独和协同地影响膜的运输特性。研究假设构型自由体积比构象自由体积稳定得多，因此即使在恶劣条件下，即在高温和具有化学挑战性的环境下，它也具有前所未有的抗物理老化和塑化能力。本文将系统地合成具有不同自由体积结构的iptyene基聚合物，并研究构型自由体积对分子运输的影响。基本输运性质（即吸收、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，将进行原子模拟来阐明基于构型自由体积的聚合物中的潜在输运机制和纳米约束的影响。该项目的成果将改进用于工业气体分离的膜，特别是在恶劣条件下。该奖项反映了美国国家科学基金会的法定使命，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。

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.