Facile method to prepare Pd/Polystyrene composite microspheres and investigation on their catalytic properties

摘要

Nano-sized Pd/polystyrene composite nano-particles were prepared via surfactant-free emulsion polymerization. The as-prepared composite particles were used as a catalyst for Suzuki reaction, and they showed excellent catalytic properties in the conversion and recyclability. First, polystyrene (PS) latex particles bearing carboxyl groups on the surfaces were synthesized via one-stage surfactant-free emulsion polymerization employing acrylic acid as the functional monomer. Thus, made the PS particles negatively charged and could attract positively charged Pd~(2+) ions. By adding PdCl_2 solution to this functional polystyrene emulsion, Pd~(2+) ions were attached to the surfaces and reduced to zero valent particles by the reducing agent, NaBH_4. Nano-sized Pd/PS composite particles could be synthesized via this facile method. The amount of the functional monomers, the Pd~(2+) content and the amount of the initiator played important roles to the final morphologies of the composite particles. The resulting composite microspheres were observed by TEM. Furthermore, catalytic properties of the as-prepared Pd/PS composite particles were studied via Suzuki reaction, and the results were characterized by FTIR and ~1H-NMR. The Pd/ PS composite particles showed excellent conversion and could be recycled easily for reuse. After each round of Suzuki reaction, the Pd/PS composite particles could be separated just by filtration, the conversion still remained as high as 70.2 %, even when used 5 times.