CAREER: Binucleating Bis(pyrazolyl)alkanes for Tractable Bimetallic Polymerization

With the support of the Chemical Catalysis Program in the Division of Chemistry, Robert Comito of the University of Houston is developing bimetallic catalysts for the synthesis of biodegradable polymers. Currently, most synthetic plastics and elastomers are prepared from petrochemicals and are neither biodegradable nor biocompatible. Although some biodegradable polymers have been developed as replacements for petrochemical ones, their synthesis requires different catalysts than those used for petrochemicals that are not well understood. The goal of the Comito research program is to develop a new platform of catalysts for biodegradable polymer synthesis by focusing on the cooperation between multiple metal sites. These studies are focused on finding new catalysts that can be tuned to prepare biodegradable polymers with novel structures, new physical properties, and improved performance. These activities are further being used to train a diverse group of students in organometallic chemistry, catalysis, and polymer synthesis with emphasis on the inclusion of undergraduates, first-generation scholars, and underrepresented groups in STEM (science, technology, engineering and mathematics) disciplines. Moreover, the technical knowledge generated through this research program is being converted into publicly available educational materials for teaching mechanistic analysis to graduate students and reaction mechanisms to undergraduates. Under this award, Robert Comito and his research team are developing ligands for the proximal coordination of two main group metals for cooperative catalysis toward the controllable synthesis of biodegradable polymers. The hypothesis underlying this research program is that the catalytic polymerization of esters and carbonates by main group metals inevitably involves multi-metallic mechanisms. Considering that metal-bridging coordination of an alkoxide chain end and bifunctional insertion of the monomer feedstock are essential features of chain growth during polymerization, Comito and his group are evaluating the orientation, distance, and substitution of adjacent catalytic metal sites to identify the controlling mechanistic features of main-group catalyzed polymerization that produce unique polymer structures. Applying these skills in mechanistic analysis toward teaching, Dr. Comito is generating drag-and-drop teaching materials that will improve the instruction of reaction mechanisms in a digital format. He is also generating pedagogical materials on control experiments, a class of experiments essential toward understanding mechanisms in science but which are rarely taught in the classroom. 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.