A process for the polymerization of one or more addition polymerizable monomers and the resulting polymer products, said process comprising: 1) contacting an addition polymerizable monomer or mixture of monomers under addition polymerization conditions in a reactor or reactor zone with a composition comprising at least one olefin polymerization catalyst and a cocatalyst and characterized by the formation of polymer chains from said monomer or monomers; 2) transferring the reaction mixture to a second reactor or reactor zone and optionally adding one or more additional reactants, catalysts, monomers or other compounds prior to, commensurate with, or after said transfer; and 3) causing polymerization to occur in said second reactor or reactor zone to form polymer chains that are differentiated from the polymer chains formed in step 1); said process being characterized by addition of a chain shuttling agent to the reaction mixture prior to, during, or subsequent to step 1) such that at least some of the resulting polymer molecules from step 3) comprise two or more chemically or physically distinguishable blocks or segments.