The Development and Study of Protein Photocatalysts for Photoinduced Electron/Energy Transfer Reversible Addition-Fragmentation Chain Transfer Polymerizations

Abstract

This dissertation reviews literature relevant to the broader project of Biocatalyst Development for photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) Polymerizations. Chapter 1 traces the history of reversible deactivation radical polymerization (RDRP) and discusses the utility of photo electron/energy Transfer (PET) catalysis in RAFT polymerizations. We report, for the first time, an inherently photoactive protein that catalyzes PET-RAFT polymerizations. Zinc myoglobin (ZnMb) was identified as an inherently photoactive protein that was uniquely suited to photoinduced electron/energy transfer chemistry, and this protein was synthesized and used for PET-RAFT polymerizations. ZnMb proved to perform well, demonstrating all of the required features for a well-controlled polymerization, such as linear pseudo-first-order kinetics, linear growth in molecular weight with conversion, and maintained living chain ends, as evidenced by successful chain extension experiments. Inspired by the method developed for using ZnMb as a protein photocatalyst, we aimed to explore some of the consequences of using a protein in polymerization. For instance, we examined how polymer molecular weight affects chain-extension kinetics due to steric interactions with a restricted protein active site. Additionally, we investigated other reaction parameters to tune when using a protein, such as buffer composition and resulting protein stability. We demonstrate that by changing buffer composition and adjusting the salinity of the mixture, we can alter the kinetic performance of the polymerization while still maintaining a well-controlled process, as evidenced by linear pseudo-first-order kinetics, linear growth in molecular weights, and low dispersities.