Suppression of Chain Transfer at High Temperature in Catalytic Olefin Polymerization

Abstract

Living polymerization by suppressing chain transfer is a very useful method for achieving precise molecular weight and structure control. However, the suppression of chain transfer at high temperatures is extremely challenging in any catalytic polymerization. This has been a severe limitation for catalytic olefin polymerization, which is one of the most important chemical reactions. Here, we report the unprecedented living polymerization of ethylene at 130 °C, with a narrow molecular weight distribution range of 1.04 to 1.08. This is a significant increase in the reaction temperature. Tailor-made α-diimine nickel catalysts that exhibit both the steric shielding and fluorine effects play an essential role in this breakthrough. These nickel catalysts are even active at 200 °C, and enable the formation of semi-crystalline, ultrahigh-molecular-weight polyethylene at 150 °C. Mechanistic insights into the key chain transfer reaction are elucidated by density functional theory calculations.