New families of highly branched polyethylenes containing alkyl short chains branches as well as polar and non-polar long-chain branches were prepared by combining migratory insertion copolymerization with controlled radical graft copolymerization. Key intermediate was a novel alkoxyamine-functionalized 1-alkene which was copolymerized with ethylene using a palladium catalyst. The resulting highly branched polyethylene with alkoxyamine-functionalized short chain branches was used as macroinitiator to initiate controlled radical graft copolymerization of styrene and styrene/acrylonitrile. Novel polyethylene graft copolymers with molecular masses of Mw > 100 000 g/mol and narrow polydispersities were obtained. Transmission electron microscopic studies (TEM) and the presence of two glass transition temperatures at -67 and +100 degrees C indicated microphase separation.