A process for forming a high molecular weight, multi-block copolymer comprising two or more chemically distinguishable segments or blocks, the process comprising polymerizing one or more olefin monomers in the presence of a chain shuttling agent and a catalyst composition comprising two or more olefin polymerization catalysts capable of preparing polymers having differing chemical or physical properties under equivalent polymerization conditions, or a catalyst composition comprising at least one olefin polymerization catalyst containing multiple active catalyst sites capable of preparing polymers having differing chemical or physical properties.