| 초록 |
By suppressing all the chain transfer reactions, living polymerization of ethylene with a metallocene catalyst has been achieved. It has been found that aluminum transfer is the only chain transfer reaction with Cp*2ZrCl2/MAO at 0°C, presumably because sterically hindered bis-pentamethylcyclopentadienyl ligand blocks β-agostic interaction. Removing trialkylaluminum compounds from the polymerization system is enough to prevent chain termination, and the polymerization undergoes in a living fashion. However, due to the steric hindrance between the ligand and the polymer chain, propagating species are more active than initiating species resulting in broad initial molecular weight distribution. By controlling initiation steps polyethylene with narrow PDI (~1.1) and ultra high molecular weight polyethylene (~106) were obtained.
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