Tandem Copolymerization: An Effective Control of the Level of Branching and Molecular Weight Distribution

The term ‘‘tandemcatalysis’’ addresses the action of two or more different catalysts in a single reactor to yield a product that is otherwise inaccessible to the individual catalysts. Its application to the production of branched polyethylene from ethylene feedstock as well as of homopolymers or copolymers with controlled molecular weight distribution is a relatively recent and successful technique. A great variety of combinations of late and early metal precursors, in different experimental conditions, have been successfully employed in tandem processes to prepare polyolefins with improved properties and performance parameters. In this article, we report on two examples of tandem catalysis, where either cooperative or independent actions take place.