Thermally Robust and Redox Active Catalysts: Studying Their Behavior for Ethylene and L-lactide Polymerization

The development of homogenous single-site catalysts has significantly impacted the field of organometallic chemistry. The well-defined structures of homogenous catalysts make it less cumbersome to understand and develop methods to tailor these compounds for specific catalytic processes. Currently, polymerization catalysis is a major division in organometallic chemistry due to the global demand for polymeric materials such as polyethylene (PE) and polypropylene (PP), based on their low-cost feedstock, remarkable mechanical properties, and their use in a wide range of applications. However, bioplastics have become a highly sought-after alternative to conventional petrochemical-based plastics due to their biodegradability and derivatization from renewable resources. Specifically, polylactic acid (PLA) has shown tremendous promise for a variety of applications including medical and packaging products. With such a high demand for these materials, there is a great desire to understand and to be able to control the polymerizations of monomers such as ethylene and lactide.

This dissertation will describe several advances the Long group has taken toward designing advanced single-site catalysts for the polymerization of ethylene and L-lactide. In our studies, we have determined that catalyst design can have a major impact on polymerization behavior and catalyst stability. More specifically, our group has been particularly successful in (1) designing thermally robust catalysts for ethylene polymerization and (2) designing redox-switchable catalysts for L-lactide polymerization. To date, our group has published several fundamental studies encompassing thermally robust catalysts for polyethylene and the development of redox-switchable catalysts for PLA. A portion of these results will be described herein.