This award is made in the Materials Chemistry and Chemical Processing Initiative in support of the collaborative research of Professors Schrock, Cohen and Silbey at MIT. Joint funding is provided by the Divisions of Chemistry and Materials Research. The thrust of the research is the synthesis and study of semiconductor clusters of uniform size. These clusters are expected to have properties markedly different from the same bulk materials. Ring-opening metathesis polymerization by well-characterized molybdenum catalysts will be used to prepare block copolymers with morphologies consisting of uniform sized spheres within a host polymer matrix. The spherical regions will contain main group metals covalently attached to each monomeric unit in the region. The host polymer will be a hydrocarbon. Block copolymer films will be treated with hydrogen sulfide in order to generate uniform sized clusters within the spheres. Optical spectra will be acquired and evaluated using theoretical techniques. Selenides, tellurides, phosphides and arsenides of a variety of main group elements should be preparable using similar approaches. Lead sulfide clusters with an average size of 30 angstroms have been prepared in a polynorbornene film.