Microstructural Control in Metal-Free Ring-Opening Metathesis Polymerization

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Andrew J. Boydston of the University of Wisconsin-Madison will mechanistically investigate polymer structural control in metal-free ring opening metathesis polymerization. Ring opening metathesis polymerization is a type of polymerization that can be used to produce a variety of useful materials, many of which are considered high-performance plastics since they display remarkable toughness and durability. Such materials are greatly needed in areas such as light-weighting of vehicles to improve energy efficiency, ballistic impact resistant composition, and even 3D printing. In this research, systematic studies will be performed to gain understanding of how the specific three-dimensional arrangement of atoms in the polymer structure is controlled during polymerization. Successful advancement of this new polymerization method has the potential to provide useful information for further developments of synthetic organic chemistry, polymer synthesis, and light induced catalysis. This work will provide training and education to undergraduate and graduate students in synthetic polymer chemistry, and collaborative research activities with other university researchers. Outreach activities will focus on workshops to middle and high school visitors to the University of Wisconsin-Madison, and an Educators Open House to increase interest in science at local high schools. This research will focus on the mechanistic understanding of polymer microstructural control in photoredox-mediated ring opening metathesis polymerization initiated by vinyl ethers. Careful studies will be conducted to investigate steric and electronic interactions that govern the orientation of neighboring repeat units in the polymer chains. The unique mechanism of vinyl ether activation in this polymerization will be leveraged to investigate new strategies for controlling polymer stereochemistry and chain-end functionalization. A mechanistic hypothesis based upon ion-pairing interactions will be evaluated, and the results will be used to design synthetic strategies for currently inaccessible stereoblock copolymers as well as generalizable methods for reducing molecular weight dispersity of the polymer products. These studies have the potential to provide opportunities to complement, validate, and challenge existing hypothesis and assumptions in a broad range of research areas. The metal-free, radical cation-based polymerization methodology being developed in these laboratories has the potential to provide access to classes of polymers that are challenging to produce using metal-based initiators. 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.