Synthesis and applications of palladium-coated poly(vinylpyridine) nanospheres

Monodisperse poly(4- and poly(2-vinylpyridine) nanospheres in the 500 nm di ameter range were prepared by emulsifier-free emulsion polymerization techn iques under free radical initiation of the respective monomers with 4 wt % divinylbenzene as the cross-linking agent. The size, integrity, and nature of the nanospheres were investigated by Scanning electron microscopy, trans mission electron microscopy, energy-dispersive X-ray analysis, Auger spectr oscopy, and Fourier-transform infrared spectroscopy measurements. The rigid and highly stable nanospheres with exposed pyridine nitrogen on the surfac e serve as an excellent support; for Pd-0 nanoparticles in the range of 1-4 nm. The Pd-coated nanospheres were also characterized by transmission elec tron microscopy and inductively coupled plasma mass spectrometry measuremen ts. Four weight percent palladium-coated nanospheres serve as good catalyst s for Suzuki-, Heck-, and Stille-type coupling reactions for carbon-carbon bond formation.