(675e) Siloxane Polymer Assisted Synthesis of (sub)Nanometer Metal Particles of Controlled Sizes

Synthesis of nano-size metal particles with the aid of soluble polymer protective groups has the potential of fine control of the particle size. Unlike the more common method of using reverse micelle as templates, which is very restrictive as micelles are generally stable only when the surfactant concentration is very low, leading to the use of large volumes of solvents, soluble protective polymer method affords much higher concentration operation, with the additional advantage of molecular control via chemical composition of the polymer. However, for both of these methods, additional steps of introducing the metal nanoparticles onto a support and removal of the surfactant or protective polymers to form supported catalysts often prove problematic. Here, we describe the use of a siloxane polymer to form controlled size metal nanoparticles in the nanometer and sub-nanometer size range. The siloxane polymer is derivitaized such that it serves as both the reductant and chemical and steric anchor for the metal nanoparticles. The degree and nature of derivatization are used to tune the particle size. Subsequent encapsulation of the siloxane-metal composites via sol gel catalysis using metal alkoxides followed by thermal decomposition of the metal alkoxide and siloxane polymers yielded supported metal catalyst.