Characterization of Polymer Brushes on Nanoparticle Surfaces

Polymer brushes have been prepared through metal-mediated, surface-initiated polymerization (SIP) from gold and silica nanoparticles such that all parameters of the resulting nanocomposite material are under synthetic control. Gold and silica nanoparticles provide unique model systems for testing theories of polymer brush synthesis in confined geometries, and are also useful for screening chemical variations for SIP schemes. Specifically, titanium alkoxide-mediated polymerizations of polyhexylisocyanates were performed from gold nanoparticles that were stabilized with mixed layers of thiols containing terminal hydroxyls, and ruthenium alkylidenes were bound to norbornene functionalized Stober silica for the ring-opening metathesis polymerization of norbornene monomers. These two different nanoparticle/ polymer brush systems were analyzed for brush thickness, polymer molecular weight, and particle size. Detailed information on initiation efficiency and on the density of chain attachment points will ultimately lead to future refinements in preparation of polymer brushes using the “grafting from” or SIP approach.