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

Monodisperse poly(4- and poly(2-vinylpyridine) nanospheres in the 500 nm diameter range were prepared by emulsifier-free emulsion polymerization techniques 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, transmission electron microscopy, energy-dispersive X-ray analysis, Auger spectroscopy, and Fourier-transform infrared spectroscopy measurements. The rigid and highly stable nanospheres with exposed pyridine nitrogen on the surface 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 electron microscopy and inductively coupled plasma mass spectrometry measurements. Four weight percent palladium-coated nanospheres serve as good catalysts for Suzuki-, Heck-, and Stille-type coupling reactions for carbon-carbon bond formation.