Nanoparticle functionalization and grafting-from chemistry for controlling surface properties and nanocomposite behavior
Nanoparticles were functionalized in order to incorporate their unique properties into functional materials. Gold nanoparticles were functionalized to direct their assembly at the oil-water interface, and further modified to achieve cross-linking at the interface, incorporation of charged groups or targeting groups, and extrusion to resize the capsules for potential delivery applications. Capsules were characterized by fluorescence microscopy by encapsulation of a fluorescent dye, and after drying on substrates by scanning force microscopy (SFM) and transmission electron microscopy (TEM). Gold nanoparticles were functionalized for their assembly into a microphase separated block copolymer, polystyrene-b-poly(2-vinyl pyridine) (PS-PVP) and the nanoparticles were directed within the domains by modification of the ligand periphery. Varying the ratio of hydrophobic to hydrophilic ligands allowed for the controlled assembly of the nanoparticles within the PVP domain of the diblock copolymer or at the interface between the two blocks. Thermal annealing resulted in ripening of the particles and migration of all particles to the center of the PVP domain. Location of the nanoparticles was determined by TEM and SFM. Gold nanoparticles were modified with acid-labile groups for potential use in photolithography applications, and with amine groups for incorporation in water purification membranes. Silica particles were modified with a dithiocarbonate chain transfer agent to achieve controlled polymerization by reversible addition fragmentation chain transfer polymerization (RAFT) of vinyl acetate from the particle surface. The poly(vinyl acetate) was hydrolyzed to poly(vinyl alcohol) to achieve particles dispersible in water with potential gas barrier properties. Functionalized silica particles were characterized by thermogravimetric analysis, TEM, and polymer was characterized by size exclusion chromatography.