Strategies for the Preparation of Functional Pendant Group Polymer Materials via Click Chemistry
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.