Exploring Metal-Free Living Cationic Polymerizations via Reversible Addition-Fragmentation Chain Transfer

点击翻译按钮获取中文摘要

Synthetic polymers (commonly known as plastics) are a mixture of different molecular "strings" having different lengths. While for many applications, such a mixture does not impact the physical properties of the polymer, some applications require polymers to have strings of the same length to attain specifically-desired polymer properties. The research group of Professor Wei You at the University of North Carolina Chapel Hill has discovered a new polymerization methodology for preparing polymers that have a narrow distribution of lengths. To further develop the methodology, this research seeks a better understanding of the polymerization process in order to achieve greater control of the lengths of such molecular strings. The research also seeks to broaden the applicability of the synthesis methods to a wide range of different polymers. Education, collaboration, and outreach are integral aspects of this project. Professor You actively recruits students of underrepresented groups into his research group. Graduate, undergraduate, and high school students receive training in cutting-edge small molecule and polymer synthetic methods, along with complex analytical techniques through engaging in this interdisciplinary research project. Professor You is actively involved in a number of outreach activities, including the UNC Science Expo (part of the North Carolina Science Festival). This event is UNC?s single largest science outreach event, attracting approximately 10,000 participants annually. In addition, Professor You has also designed short lectures on polymer solar cells for high school students and teachers brought as part of the Climate LEAP program.The classical living cationic polymerization achieves "living" characteristics via the equilibrium between the ionic (i.e., propagating chain end) and the covalent (i.e., resting chain end) species. In contrast, the controlled cationic polymerization recently discovered in Professor You's laboratory proceeds through an entirely new mechanism - a cationic chain transfer mechanism, analogous to that of the conventional Reversible Addition-Fragmentation Chain Transfer (RAFT) radical polymerization. This research explores and elucidates the mechanism of this new cationic polymerization process. The project investigates the mechanistic details of a new metal-free, protonic acid initiated and alcohol-mediated controlled cationic polymerization. The researchers expand this unique living cationic polymerization into polymerizing various electron-rich monomers, and unveiling the roles of the applied photocatalysts in the controlled cationic RAFT polymerization.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.