Abstract
Novel living polymerization catalysts for the synthesis of substituted polyacetylenes were developed on the basis of design of Rh catalysts. Phenylacetylene (PA), which is one of the typical substituted acetylene monomers, was applied to a newly developed ternary catalyst consisting of [(tfb)RhCl]2/LiCPh=CPh2/Ph3P (tfb=tetrafluorobenzobarrelene). The polymer that formed with the ternary catalyst showed the narrowest molecular weight distribution (MWD, Mw/Mn=1.04) among those reported so far. A vinylrhodium complex ([(tfb)Rh(CPh=CPh2)(PPh3)]), which has the structure of the proposed initiating species, could be isolated in high yield. This Rh complex also effected the living polymerization of PA in the presence of Ph3P ligand. Compared to the previously developed analogous catalyst bearing 2,5-norbornadiene (nbd) as a ligand, the tfb catalyst gives better-defined poly(phenylacetylene) (PPA). The syntheses of poly(macromonomers), which have PPA mainchains and either polystyrene or poly(methyl methacrylate) side chains, were accomplished using both Rh-based classic and living polymerization catalysts namely [(nbd)RhCl]2/Et3N and [(nbd)Rh(CPh=CPh2){P(4-FC6H4)3}]/(4-FC6H4)3P. The former catalyst afforded graft polymers having high molecular weights and relatively broad MWDs, while the latter gave polymers with much narrower MWDs with lower molecular weights.
