SYNTHESIS OF PALLADIUM AND PLATINUM NANOCLUSTERS WITHIN MICROPHASE-SEPARATED DIBLOCK COPOLYMERS

Small palladium and platinum clusters have been synthesized within a purely hydrocarbon polymer matrix. The procedure consists of ring-opening metathesis polymerization of norbornene-derived organometallic complexes, Pd(Cp(N))(PA) and Pt(Cp(N))Me3 (Cp(N) = endo-2-(cyclopentadienylmethyl)norborn-5-ene and PA = eta-3-1-phenylallyl), using W or Mo alkylidene initiators, followed by static casting of films and subsequent reduction of the organometallic complexes under mild conditions using molecular hydrogen. Diblock copolymers of the organometallic monomers and methyltetracyclododecene (MTD) also were prepared. Under suitable conditions these copolymers underwent microphase separation, resulting in lamellar, cylindrical, and spherical morphologies. The metal clusters formed in the copolymer films exhibiting lamellar and cylindrical morphologies were predominantly within the original metal-containing microdomains, had a narrow size distribution compared to the clusters formed in the homopolymer films, and were less than 100 angstrom in diameter.