Rhodium-catalyzed phenylacetylene polymerization in compressed carbon dioxide

Polymerization of phenylacetylene using rhodium catalysts can be carried ou t with high efficiency in compressed (liquid or supercritical) CO2. Using t he complex [(nbd)Rh(acac)] (nbd = 12,5-norbornadiene, acac = acetyl acetona te) as a catalyst precursor, the polymerization rate in CO2 is considerably higher than in conventional solvents such as THF or hexane. The resulting polymers consist of THF-soluble (mainly cis-transoidal) and THF-insoluble ( mainly cis-cisoidal) species. The polymer characteristics such as stereoreg ularity and molecular weight are compared to those obtained by polymerizati on in conventional solvents. Addition of {4-F(CF2)(6)(CH2)(2)C6H4}(3)P give s rise to a ligand-modified rhodium catalyst with high solubility in compre ssed CO2 and leads to an increase in selectivity toward the cis-transoidal polymer.