Synthesis of a novel branched–hyperbranched diblock polyolefin via chain walking and chain transfer polymerization from ethylene alone

Abstract

A new strategy was explored to achieve hyperbranched–branched diblock polyolefin from ethylene alone via chain walking and chain transfer polymerization. In ethylene polymerization process, {2,6-iPr2–C6H3 N=C(CH3)–(CH3)C=N–iPr2 –C6H2}NiBr2/methylaluminoxane/ZnEt2 first produced hyperbranched polyethylene chains via rapid chain walk under 40 °C and then, prepared branched chains via moderate chain walk at 0 °C. ZnEt2, as chain transfer agent, was added into catalyst system to facilitate reversible chain transfer between nickel metal active centers and zinc metal inactive centers to synthesize hyperbranched–branched diblock polyolefin. The resultant polyethylenes were analyzed by gel permeation chromatography and 13C NMR spectra and the results indicated that hyperbranched–branched diblock polyolefin was successfully synthesized via chain walking and chain transfer polymerization.