Date of Award
Open Access Dissertation
Chemistry and Biochemistry
Brian C. Benicewicz
This work focused on using polymers to modify the surface of various inorganic substrates, ranging from TiO2, ITO, CDSe and CdS nanostructures to micron sized silica particles. The synthesis of the polymers using the RAFT technique and the characterization of the functionalized substrates were analyzed in detail to provide insights into their use for various applications. In the first part of this work, novel phosphate based RAFT agents and phosphate containing polymers, including poly(methyl methacrylate) (PMMA), poly(glycidyl methacrylate) (PGMA) and poly(dimethyl siloxane) (PDMS) were synthesized. Alkyne functionalized PGMA was used to click to ITO surfaces in a grafting-to method, and a phosphate based RAFT agent was utilized to demonstrate the first example of PMMA grafted from ITO nanoparticles. Using commercially available hydroxyl-modified PDMS, the PDMS-phosphate was synthesized and anchored to TiO2 nanoparticles using both monomodal and bimodal approaches. The second part of this thesis focused on the development of imidazole functionalized polymers for attachment to quantum dot materials. Activated esters were directly copolymerized with poly(ethylene glycol) methacrylate (PEGMA) followed by postmodification with histamine to obtain water soluble multidentate imidazole copolymers. The applicability of these polymers in functionalizing and stabilizing CdSe quantum dots was investigated, resulting in good quantum yields of the functionalized dots as well as excellent dispersions in water. Detailed polymerization studies were conducted to determine the reactivity ratios for this important monomer pair. In the third section, the earlier fundamental studies on the polymerization of activated esters were expanded by adding a boc-protected methacrylamide to the methacrylate based activated ester and PEGMA. Due to the intrinsic differences in the electronegativity of the groups next to the vinyl bond, the vinyl groups displayed unique NMR signals, and allowed for the measurement of the individual monomer conversions in the terpolymer system. The terpolymer was postmodified with imidazole units, followed by the boc-deprotection of the amine terminal groups. The resulting poly(imid-PEGMA-MAMimine) provided water solubility, dye loading capability and well as the ability to coordinate with CdS surfaces using the imidazole units. Upon the attachment of a rhodamine dye, studies to analyze the potential of such polymers to modify CdS nanowires were performed using florescence spectroscopy. The results also showed that the carefully designed terpolymers were more effective as a labeling species than the free dyes. Finally, the fourth part of the thesis investigated additional monomer classes and particle types for functionalized polymer applications. In this section, the synthetic toolbox was expanded by studying the growth of poly(acrylic acid) and poly(acrylamide) (PAM) on larger porous silica particles (5.5 μm) using RAFT. Additionally, a novel activated azo initiator was also shown to polymerize methyl methacrylate and styrene from the silica surface as a cost-effective alternative to RAFT. In a demonstration of this technology for environmentally friendly fracturing fluids, migration studies were designed by passing the silica-polymer samples through columns of filter material to show that the polymer-anchored samples were retained in the filter media more than unfunctionalized silica particles.
Viswanath, A.(2014). Surface Functionalization of Inorganic Substrates with Polymeric Ligands Using Raft Polymerization. (Doctoral dissertation). Retrieved from http://scholarcommons.sc.edu/etd/3044