CAREER: Systematic Design of Polymers to Reveal the Anomalous Role of Fluorine on Membrane-based Separations

聚合物膜通过去除各种工艺流程中的污染物，可能会使美国经济的许多部门受益，包括制造业、化学品生产、医疗保健和国防。然而，制造这些膜所需的材料缺乏当前和新兴应用所需的效率、生产力和稳定性。为了填补这一空白，并为美国经济的各个部门提供广泛的增长机会，需要进行基础研究，以开发新的材料设计策略。这一建议的重点是一类独特的聚合物，氟共价连接到他们的结构。与所有其他已知的聚合物不同，这些含氟聚合物在理论上具有意想不到的和有益的能力，可以从各种产品中分离污染物。为了揭示这些能力背后的原因，我们将对一系列含氟量不同的聚合物进行表征，以揭示氟对膜基分离的效率、生产率和稳定性的提高所起的作用。此外，该提案将发展聚合物奇才项目，将麻省理工学院的本科生和研究生与科学和工程领域代表性不足的高中生和中学生联系起来。本课程将涉及与聚合物相关的亲自授课和动手实验，提供这些实验与分子分离之间的相关联系。为这一项目开发的课程也将被录制成视频，并通过在线平台传播，以促进更广泛的参与。最后，本提案旨在通过与MIT UROP计划、MIT ACCESS计划和NetPals合作，吸引新一代研究人员进入分离科学领域。通过UROP计划，将做出具体努力，为女学生和代表性不足的少数民族在这项提案的研究项目中提供更多机会。与其他非极性分子不同，全氟分子与非氟物质结合时不服从热力学混合理论。这种分解在理论上对膜基气体分离具有重要意义。对于某些工业上相关的气体对，全氟聚合物具有所有已知聚合物中最佳的渗透性和选择性组合，并且这些材料还表现出前所未有的物理老化稳定性和抗塑化性。然而，这种理论异常的起源还没有得到很好的理解。因此，本课题主要考虑氟对膜分离性能的影响。为了实现这一目标，该项目将利用大分子合成的策略来设计高分子量的玻璃状聚合物，并在聚合物的主链上附加不同数量的氟。这些努力将与先进的材料和传输特性相辅相成，研究结果将通过理论和模拟来解释。通过这样做，假设驱动的问题将被测试，以调查为什么氟出乎意料地增加选择性，减少物理老化，并提高膜基气体分离的抗塑化能力。从更广泛的角度来看，本提案旨在发表关于参考材料和参考标准的同行评议论文，以在膜社区中实现更强大的测量技术。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。

Polymer membranes would potentially benefit many sectors of the U.S. economy, including manufacturing, chemicals production, healthcare, and defense, by removing contaminants from various process streams. However, the materials needed to make these membranes lack the efficiency, productivity, and stability that is often required for current and emerging applications. To fill this gap and provide broad opportunities for growth in various sectors of the U.S. economy, fundamental research is needed to develop new materials design strategies. This proposal focuses on a unique class of polymers that have fluorine covalently attached to their structure. Unlike all other known polymers, these fluoropolymers have theoretically unexpected and beneficial abilities to separate contaminants from various products. To uncover the reason behind these abilities, a series of polymers with varying amounts of fluorine will be characterized to reveal the role of fluorine on enhanced efficiency, productivity, and stability for membrane-based separations. Additionally, this proposal will develop the Polymer Prodigies program to connect undergraduate and graduate students from MIT with high school and middle school students who are underrepresented in science and engineering. This program will involve in-person lectures and hands-on experiments related to polymers, providing relevant connections between these experiments and molecular separations. Curriculum developed for this program will also be recorded as videos and disseminated through online platforms to promote broader engagement. Finally, this proposal seeks to attract a new generation of researchers to the field of separation science through collaboration with the MIT UROP program, MIT ACCESS Program, and NetPals. Through the UROP program, specific efforts will be made to bolster opportunities for female students and underrepresented minorities in research projects for this proposal.Unlike other nonpolar molecules, perfluorinated molecules do not obey thermodynamic mixing theories when combined with non-fluorinated species. This breakdown in theory has important implications for membrane-based gas separations. For certain industrially relevant gas pairs, perfluoropolymers have the best combinations of permeability and selectivity of all known polymers, and these materials also exhibit unprecedented stability to physical aging and a resistance to plasticization. However, the origins of this theoretical anomaly are not well understood. Therefore, the main consideration of this proposal is to investigate the role of fluorine on membrane separation performance. To accomplish this goal, this project will leverage strategies in macromolecular synthesis to design glassy polymers of high molecular weight with varying amounts of fluorine appended to the backbone of the polymer. These efforts will be complemented with advanced materials and transport characterization, and findings will be interpreted through theory and simulations. By doing so, hypothesis-driven questions will be tested to investigate why fluorine unexpectedly increases selectivity, reduces physical aging, and improves plasticization resistance for membrane-based gas separations. From a broader perspective, this proposal seeks to publish peer-reviewed papers on reference materials and reference standards to enable more robust measurement techniques within the membrane community.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.