Regioselective Polymerizations of α-Olefins with an α-Diamine Nickel Catalyst

Abstract

Polymerizations of linear α-olefins (CnH2n, CH2 = CH―R, R = Cn−2) catalyzed by early transition metals typically afford amorphous polymers with alkyl chains (Cn−2), while chain-straightening polymerizations of α-olefins with nickel-based catalysts produce semicrystalline polyolefins. Polymerizations of various α-olefins were carried out using an α-diamine nickel catalyst with a significantly distorted chelating ring. The influences of temperature, monomer concentration, and chain length of α-olefins on polyolefin microstructure were examined in detail. The α-diamine nickel catalyst realized highly regioselective 2,1-insertion of α-olefins regardless of reaction temperature and monomer concentration. Increased chain length of α-olefins led to the formation of more linear polyolefin. Semicrystalline polyolefins with high melting temperatures (Tm) were made from α-olefins through highly regioselective 2,1-insertion and precise chain-straightening.