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.