Uniform star-polystyrene nanoparticles prepared by emulsion atom transfer radical polymerization

Pentaerythritol (PT) was converted into four-arm initiator pentaerythritol tetrakis(2-chloropropionyl) (PT-Cl) via reaction with 2-chloropropionyl chloride. Uniform (monodisperse) star-polystyrene nanoparticles were prepared by emulsion atom transfer radical polymerization of styrene, using PT-Cl/CuCl/bpy (bpy is 2,2'-dipyridyl) as the initiating system. The structures of PT-Cl and polymer were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The morphology, size and size distribution of the star-polystyrene nanoparticles were characterized by transmission electron microscopy, atomic force microscopy and photon correlation spectroscopy. It was found that the average diameters of star-polystyrene nanoparticles were smaller than 100 nm (30-90 nm) and monodisperse; moreover, the particle size could be controlled by the monomer/initiator ratio and the surfactant concentration. The average hydrodynamic diameter (D-h) of the nanoparticles increased gradually on increasing the ratio of styrene to PT-Cl and decreased on enhancing the surfactant concentration or increasing the catalyst concentration. (C) 2011 Society of Chemical Industry