Radical co-polymerization of diiminedibromidenickel(II)-functionalized olefin with styrene:synthesis of polymer-incorporated nickel~(II) alpha-diimine catalysts for ethylene polymerization

摘要

alpha-Diimine nickel catalyst bearing two allyl groups [ArN=C]_2C_(10)H_6NiBr_2 (Ar=4-allyl-2,6-(i-Pr)_2C_6H_2)] (Cat-1) has been synthesized and characterized.The corresponding polymer-incorporated nickel catalysts PC and the SiO_2-supported shell-core structure catalyst SC-1 were obtained by the co-polymerization of the olefin groups of Cat-1 with styrene in the presence of a radical initiator.Radical co-polymerizations with styrene in solution were investigated in detail,and the compositions and molecular weight of the copolymers were determined.All three types of catalysts (Cat-1,PC and SC-1) have been investigated for ethylene polymerization.These catalysts were found to exhibit high activity in the presence of modified methylaluminoxane (MMAO) as a co-catalyst.Among them,the polymer-incorporated PC and SiO_2 shell-core catalyst SC-1 displayed very high activity (approx 2.62 and approx 1.11 kg (mmol Ni)~(-1) h~(-1),respectively) with product molecular weights (M_w) in the range 26X10~4 to 47X10~4 under 0.1 MPa ethylene pressure.The particle morphology of polyethylene produced by the shell-core structure catalyst SC-1 was improved.