Abstract: A combinatorial method for identifying a catalyst composition for use in the homogeneous addition polymerization of an olefin monomers, said catalyst composition comprising a transition metal compound, a cocatalyst and a polymerization modifier, as well as catalyst compositions and improved olefin polymerization processes resulting therefrom.

Abstract: A process for the polymerization of olefin monomers comprising contacting ethylene or a mixture of ethylene and one or more C4-8 ? olefins with a catalyst composition comprising one or more Group 3-10 transition metal containing, Ziegler-Natta, procatalyst compounds; one or more alkylaluminum cocatalyts; and one or more polymerization control agents, said process being characterized in that at least one such polymerization control agent is an alkyl or aryl. ester of an aliphatic or aromatic (poly)carboxylic acid optionally containing one or more substituents comprising a Group 13, 14, 15, or 16 heteroatom.