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/α-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.