Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Chemistry

Supervisor

Workentin, Mark S.

2nd Supervisor

Gilroy, Joseph B.

Joint Supervisor

Abstract

This thesis describes the development of a polymer via a unique masking-unmasking strategy allowing for physical and chemical modification as desired. Modifiable polymers may lead to improved applications in drug delivery, photo-patterning and emissive materials design. In recent years, these potential traits have motivated the search for efficient protocols for the synthetic modification of polymers. Accordingly, click chemistry, characterized by fast, clean and high yielding reactions represents an effective tool for the modification of polymers. To achieve this goal, an efficient methodology is created to incorporate a highly reactive strained alkyne functional group as a modification site to expand the post polymerization modification of polymers. A desirable family of functional groups for click chemistry are the highly reactive strained alkynes, which can undergo strain promoted alkyne-azide cycloaddition in the absence of a transition metal catalyst. Although the reactivity of the strained alkyne is desirable, it can be susceptible to side reactivity due to the highly reactive carbon-carbon triple bond. To circumvent this problem, a cyclopropenone masking group, which can undergo a decarbonylation by UV irradiation to afford the strained alkyne, can be employed. The advantage of this unmasking strategy is the fact that only CO gas is evolved, no purification is required, there is spatial and temporal control and due to the high atom economy of the polymer, and every repeating unit of the polymer backbone can be functionalized. The photochemical decarbonylation which proceeds cleanly and efficiently, liberates the strained alkyne functional group, which can form covalent bonds with azides reactions bearing substituents with specific functionality such as redox-active or emissive properties. Thus, the iii liberation of the strained alkyne and the subsequent reaction with a variety of azide reaction partners provides a robust route towards post-polymerization modification of polymers and generating a library of polymers. This thesis outlines the synthesis and characterization of a masked strained alkyne dibenzocyclooctyne-monomer, its polymerization, polymerization kinetics study and postpolymerization modification of the resulting polymer.

Summary for Lay Audience

Materials such as plastic bags and Styrofoam cups are used in our everyday lives. These materials are called polymers, and are made up of small building blocks called monomers and produced via a process known as polymerization. Most bulk polymers are designed for one specific role, which requires the physical and chemical properties to remain constant. Modifiable polymers on the other hand, allow the physical and chemical properties to be altered as desired. The goal of my thesis research was to synthesize a polymer that has the ability to be altered post polymerization. To incorporate functionality such as emissive properties for dyes or redox properties for batteries. The functional group of choice for my project was a strained alkyne, which is a highly reactive group allowing for fast and efficient reactivity. The reactivity of the strained alkyne is desired; however, it can also undergo undesirable side reactions and thus we also incorporated a masking strategy so the strained alkyne will not interfere with the polymerization process and only react when needed. The masked strained alkyne can be unmasked by treatment with UV light limiting the need for purification. Herein, I report a novel monomer, its unique masking-unmasking, polymerization and synthetic modification. The new monomer and polymers were identified using state-of-the-art analytical techniques such as nuclear magnetic resonance, UV-Visible absorption spectroscopy and mass spectrometry.

Available for download on Thursday, October 01, 2020

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