Macromolecular Design Principles: Tailoring Emergent Polymer Properties Through Microstructural Engineering

Abstract

Organic polymers are an important class of synthetic materials, with applications across an array of industries, such as textiles, plastics, electronic, and more. This diverse array of applications stems from the structural diversity available to synthetic polymers: Polymer structure can be controlled at a variety of length scales, ranging from 10-10 meters (individual chemical bonds) through 10-9 – 10-6 meters (individual polymer chains and self-assembled morphologies) to 10-3 meters (bulk materials). The bulk properties of synthetic polymer materials therefore depend upon the polymer microstructure (i.e., the chemical/molecular structure of the polymer and the resulting assembly and architecture of distinct polymer chains), which can be controlled and investigated using the tools of molecular and synthetic chemistry. By manipulating the chemical and chain structures of synthetic polymers, it is therefore possible to rationally design novel materials with tunable emergent thermal and mechanical properties. In this thesis, I describe my investigations into a variety of unique polymer microstructures, and explore the effects of microstructural changes on emergent polymer properties. Namely, I utilize the fluxional molecule bullvalene as a microstructural scrambling agent, demonstrating that incorporation of this dynamic molecule into polymer chains results in polymer chains which dynamically regioisomerism to reorient individual chains in response to mechanical stress (Chapter 2). I also advance the synthesis of cyclic polymers to enable the facile preparation of cyclic bottlebrush polymers (Chapter 3) and to enable, for the first time, the photochemical synthesis of cyclic polymers (Chapter 4). These studies include investigations into the thermal and mechanical properties of the resulting cyclic polymers, showing that they have enhanced mechanical properties relative to linear counterparts.