Date of Award

Fall 12-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

Committee Chair

Dr. Derek Patton

Committee Chair Department

Polymers and High Performance Materials

Committee Member 2

Dr. Sarah Morgan

Committee Member 2 Department

Polymers and High Performance Materials

Committee Member 3

Dr. Charles McCormick

Committee Member 3 Department

Polymers and High Performance Materials

Committee Member 4

Dr. Robson Storey

Committee Member 4 Department

Polymers and High Performance Materials

Committee Member 5

Dr. Yoan Simon

Committee Member 5 Department

Polymers and High Performance Materials

Abstract

The design and synthesis of functional, controlled polymer architectures is essential to the development of new materials with precise and tailorable properties or applications. The work described in this dissertation focuses on the development of controlled polymer architectures with dynamic linkages for the design of multifunctional materials and surfaces via robust, efficient, and stimuli-responsive strategies.

In Chapter III, a post-polymerization modification strategy based on ambient temperature nucleophilic chemical deblocking of polymer scaffolds bearing N-heterocycle blocked isocyanate moieties is reported. Room temperature RAFT polymerization of three azole-N-carboxamide methacrylates, including 3,5-dimethyl pyrazole, imidazole, and 1,2,4-triazole derivatives, afforded reactive polymer scaffolds with well-defined molecular weights and narrow dispersities (Ð < 1.2). The reactivity of the azole-N-carboxamide moieties towards nucleophiles can be tuned simply by varying the structure of the azole blocking agents. DBU-catalyzed reactions of thiols with imidazole- and 1,2,4-triazole-blocked isocyanate scaffolds were shown to occur rapidly and quantitatively under ambient conditions. Reactivity differences of 1,2,4-triazole and 3,5-dimethyl pyrazole-blocked isocyanate copolymers with various nucleophiles at room temperature facilitated sequential post-polymerization modification. This strategy advances the utility of blocked isocyanates and promotes the chemistry as a powerful postmodification tool to access multifunctional polymeric materials.

Aqueous RAFT (aRAFT) polymerization at pH=0 mediated by a novel imidazolium-containing chain transfer agent is reported in Chapter IV. In 1 M HCl, unprecedented controlled polymerization and chain-extension of unprotected acyl hydrazide methacrylamides is achieved enabling the synthesis of well-defined acyl hydrazide functionalized polymer scaffolds of interest for dynamic covalent and bioconjugation strategies. Additionally, the well-controlled aRAFT polymerization of 4-vinylimidazole is demonstrated in water for the first time. Futhermore, methods for low pH aRAFT polymerizations will afford new access to controlled polymerization of monomers with low pKa values such as 4-vinylimidazole.

In Chaper V, hydrazide-functional brush surfaces are synthesized via a combination of surface-initiated atom-transfer radical polymerization (SI-ATRP) and post-polymerization modification (PPM). Hydrazone formation, cleavage, and exchange reactions on surfaces were achieved via these hydrazide-functional brush surfaces. The dynamic nature of the hydrazone linkage was leveraged toward reversible control of surface properties. The work in this chapter serves as a powerful and robust strategy for dynamic surfaces with pH-responsive linkages.

Available for download on Saturday, December 16, 2017

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