DEVELOPMENT AND INVESTIGATION OF EXTERNALLY CONTROLLED POLYMERIZATIONS

Abstract

Controlled polymerization methodologies have been pivotal to the development of advanced polymeric materials. These methodologies take advantage of chain-growth polymerization mechanisms wherein each initiating species theoretically generates a single growing polymer chain—this leads to tunable polymer molecular weights (Mns) and molecular weight distributions (dispersity, _), and thus supports the synthesis of novel, designer materials. Despite major advancements in controlled polymerization methods, there is still significant difficulty in generating materials with highly regular structures in a controlled manner without the need for challenging multistep syntheses that often require several isolations, purifications, and chain-end modifications before the final polymer material is acquired. To overcome this challenge, we sought to explore externally controlled polymerizations as they are uniquely positioned to generate complex polymer structures and architectures due to the inherent spatiotemporal control they provide over the polymerization (Chapter 1). An in-depth mechanistic analysis of photocontrolled cationic reversible addition-fragmentation chain transfer (RAFT) polymerization was performed to gain a better understanding of the stimuli controlled polymerizations (Chapter 2). Using the mechanistic insight gained during this previous study, we sought to improve upon the previously developed photocontrolled cationic RAFT polymerization by generating efficient photocatalysts which achieve greater temporal control and extending this chemistry toward polymer chain-end modification (Chapter 3). To enable the synthesis of multiblock copolymers through a facile process, a new chemically controlled cationic polymerization was developed and paired with an orthogonal photocontrolled radical polymerization, affording the synthesis of multiblock copolymers in a one-pot process (Chapter 4). Following this, a new electrochemically controlled cationic polymerization mediated by ferrocene was developed; this process was compatibilized with a photochemically controlled radical polymerization to facilitate the in situ synthesis of higher-order multiblock copolymers than were previously achievable by similar methodologies (Chapter 5). We then sought to develop a novel set of redox controlled acids and demonstrated that large changes in acidity occur upon oxidation, thus facilitating the polymerization of cyclic monomers (Chapter 6).