Unraveling the Mechanism of Polymerization with the Phillips Catalyst

The mechanism of polymer chain growth at the Phillips catalyst has been studied, with the three prevailing mechanistic proposals, the Cosee-Arlman, Green-Rooney, and metallacycle mechanisms, considered. Through analysis of low molecular weight oligomers/polymers formed during ethylene/alpha-olefin copolymerization with labeled monomers, it is shown that the isotopomer distribution is inconsistent with a metallacycle mechanism. Further analysis of polymer formed by copolymerization of labeled ethylene was used to rule out a Green-Rooney mechanism. The results support the notion of chain growth via a Cossee-Arlman process.