AN APPROACH TO SURFACE MODIFICATIONS WITH POLYMER BRUSHES USING AQUEOUS SYNTHETIC TECHNIQUES AND CHARACTERIZATION
This thesis introduces a new emulsion polymerization technique called mini monomer encapsulated emulsion polymerization (mini ME emulsion) using activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP) to form narrow dispersity poly(methyl methacrylate), PMMA and polystyrene, PS. Subsequent chapters discuss use of this method to create polymer brushes on silica nanoparticles to form “hairy” nanoparticles, and the use of polymer brushes on silica and cellulose substrates to serve as an antibody sensor. “Hairy nanoparticles” use a combination of a polymer brush and an inorganic nanoparticle core to improve the mechanical and thermal properties of a film. Mini ME emulsion polymerization was created for the controlled polymerization of PMMA and PS in an aqueous medium. By guiding reaction localization with a phase transfer agent, tetrabutylammonium bromide (TBAB) and with acetone to control their diffusion rate, continuous feeding of the reaction loci with monomer was employed to keep a constant concentration of propagating radicals. This reaction process leads to low dispersity polymers with a predetermined molecular weight in an emulsion polymerization. Once mini ME emulsion polymerization was established in aqueous media, the polymerization method was modified to grow polymer chains on a nanoparticle surface to obtain hairy nanoparticles. Within recent years, the study of polymer brushes, which is broadly defined as polymer chains bound to a surface, has enabled ground-breaking materials with tailored interfaces, finding applications in nonfouling biosurfaces and creating novel mechanical and optical nanocomposite materials. The particles were functionalized with a hydrophobic initiator to control the polymerization loci forcing initiation to occur only within the organic phase surrounding the nanoparticle and minimizing reaction in the aqueous medium. Results of the new reaction route are described. This technique was also employed to generate polymer brushes on surfaces such as those suitable for biosensing devices and is discussed. Reaction conditions and the results of preliminary testing to these new structures for antibody sensing are described. A poly(oligoethylene glycol) methacrylate (POEGMA) polymer brush, which is used to prevent non-specific adsorption of biomolecules, was grown from cellulose or silica microparticles under aqueous conditions. These brushes were then post-modified with a model antigen, dinitrophenyl (DNP) to increase the specificity of the sensor via specific antibody-antigen recognition. Preliminary results suggest that polymer brushes are needed to increase the sensitivity of the sensor by repelling molecules that would lead to a false positive result. A sensor based on the antibody catalyzed water oxidation pathway (ACWOP) eliminates the need for a secondary antibody, thus further increasing both the specificity and sensitivity of the device and is described in this thesis.
Ober, Christopher Kemper
Baird, Barbara Ann; Abruna, Hector D.
Chemistry and Chemical Biology
Ph. D., Chemistry and Chemical Biology
Doctor of Philosophy
dissertation or thesis