Composite hydrogels: Robust carriers for catalytic nanoparticles

A new type of composite hydrogel have been synthesized in which nano-tree type polymer brush particles have been chemically entrapped in a poly(vinyl alcohol) (PVA) matrix by means of the disulfone reaction. This reaction leads to a chemical crosslinking of the nano-tree brush particles within the PVA hydrogel. Obtained composite hydrogels can be successfully used as template for the deposition of Ag nanoparticles. Field-emission scanning electron microscopy (FESEM) images demonstrate that monodisperse Ag nanoparticles (ca. 35 nm) are embedded into the composite hydrogel: Most of the silver nanoparticles were generated on the surface of the brush particles while a small amount of Ag nanoparticles was found to be entrapped within the PVA polymer network. We demonstrate that the resulting composite hydrogels can be used as a robust carrier for generation and immobilization of catalytically active Ag nanoparticles. The catalytic activity is investigated by monitoring the reduction of 4-nitrophenol by NaBH4 in the presence of such a kind of composite hydrogel. The hybrid hydrogels can be easily reused many times as a catalyst and the catalytic activity can be retained over several months.