Date of Award
Doctor of Philosophy (PhD)
Christopher N. Bowman
Jeffery W. Stansbury
Charles B. Musgrave
Stephanie J. Bryant
This thesis is focused on the preparation, characterization and implementation of polymeric colloids by a variety of heterogeneous polymerizations that are based on “click” reactions. Most commonly presented in spherical morphologies, nano/micro-particles are ubiquitous materials in coatings, composites, chromatography, drug delivery, biomedical analysis and many other applications. For decades, a variety of heterogeneous polymerization techniques have been extensively studied on the free-radical chain-growth polymerizations such as polystyrene and poly(methyl methacrylate). Due to the reaction inefficiency and its intolerance to polar solvents, conventional step-growth polymerizations are inexecutable in heterogeneous systems and thus incapable of particle preparation. Many attributes of step-growth polymers would be significant for colloidal materials, such as tunable backbone, intrinsic functionality and uniform network architecture. The “click” chemistry is an ideal toolbox to realize step-growth colloidal polymers, particularly as its high yield under mild conditions, and its orthogonality to a broad range of reagents, solvents and functional groups. Herein, firstly, thiol-Michael addition reaction polymerization is successfully carried out in miniemulsion systems. Nanoparticles with 100-200 nanometers in diameter are prepared, with capabilities of intrinsic functionality by off-stoichiometric reactions. Nanoparticles and latex films with excess acrylate undergo a second-stage radical photopolymerization, which greatly enhances their mechanical properties. Secondly, thiol-Michael addition reactions are employed in dispersion polymerization systems. Microparticles with mono/narrow size distributions are prepared, and particle sizes are dependent on the reaction kinetics. Mechanism study shows that the phase transition is primarily determined by the gelation effect. The chemical compositions and functionalities of those microparticles are proved to be uniform and precisely controllable, as demonstrated by a photo-induced tetrazole-ene reaction on the particle solid phase. Thirdly, covalent adaptable polymer particles contain either addition-fragmentation-transfer or transthioesterification moieties are prepared by both thiol-Michael and radical thiol-ene dispersion polymerizations, respectively. The adaptability of such colloids are validated in both microscopic and macroscopic materials. Further, a series of transthioesterification polymerizations are demonstrated in both linear and crosslinked systems, and are implemented in preparing dynamic covalent polymers, structurally dynamic organogels and hydrogels, and truly “recyclable” photopolymers.
Wang, Chen, "Step-Growth Nano/micro Polymer Networks" (2016). Chemical Engineering Graduate Theses & Dissertations. 7.
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