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 p olyurethane films. Then the metal ions dispersed in the polyurethane m atrix were reduced by controlling the exposure of the metal sites to N aBH4 under mild condition. The reduction of the polyurethane metal com plex films resulted in the production of amorphous ultrafine metal pow ders. The size of these powders was controlled by the content of the m etal ions and the polarity of the polymer matrix. A polar polymer back bone and lower metal ion concentration favored to achieve a smaller pa rticle. It was also found that the polymer chains prohibited the exces sive aggregation of the metal atoms and have protective effect on the final metal powders.