Prof. Dr. Axel Müller

We report on the synthesis and characterization of water-soluble stimuli-responsive organo-silica hybrid nanowires that can be used as carriers for metallic nanoparticles. The nanowires were prepared from core-shell structured cylindrical polymer brushes that served as templates with uniform size and shape. The core of the nanowires consists of a silsesquioxane network synthesized through a precursor route. The shell consists of a dense layer of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA). The hybrid nanowires exhibit a pH-responsive behavior due to the weak polyelectrolyte nature of the PDMAEMA shell. Simultaneously, the shell of PDMAEMA acts as nanoreactor for the synthesis and immobilization of metal nanoparticles. It was further quaternized with methyl iodide, leading to a poly{[2-(methacryloyloxy)ethyl] trimethylammonium iodide} (PMETAI) cationic polyelectrolyte shell around the silsesquioxane core. The as-synthesized cationic organo-silica hybrid nanowires are sensitive to salt concentration in terms of their hydrodynamic radius. They can be functionalized with Pt nanoparticles as well, leading to stable composites of the nanowires and the Pt-nanoparticles. The nanocomposites show high catalytic activity, as kinetically analyzed in the reduction of 4-nitrophenol by sodium borohydride.