Preparation of ultrafine metal particles/polyurethane composites

A new type of coordination polyurethane was prepared by incorporating the transition metal ions into the pyridine containing thermoplastic polyurethane films. Then the metal ions dispersed in the polyurethane matrix were reduced by controlling the exposure of the metal sites to NaBH4 under mild condition. The reduction of the polyurethane metal complex films resulted in the production of amorphous ultrafine metal powders. The size of these powders was controlled by the content of the metal ions and the polarity of the polymer matrix. A polar polymer backbone and lower metal ion concentration favored to achieve a smaller particle. It was also found that the polymer chains prohibited the excessive aggregation of the metal atoms and have protective effect on the final metal powders.