Positive Effect of Polar Solvents in Olefin Polymerization Catalysis

Olefin polymerization that produces the world's most important plastic by scale is one of the most important chemical reactions. Heteroatom-containing polar compounds are usually detrimental to olefin polymerization because they are prone to deactivate catalysts. In this contribution, we now report a desirable positive effect of polar solvents in ethylene polymerization. Key is the finding of a sandwich-like neutral salicylaldiminato nickel catalyst by the combination of 8-arylnaphthyl and dibenzosuberyl groups. In comparison with toluene and xylene as hydrocarbon solvents, tetrahydrofuran and 1,4-dioxane as polar solvents bring about an increased polymer molecular weight, elevated turnover frequency, narrower molecular weight distribution, and unaltered branching density. This thus promotes ethylene polymerization in a living manner (Mw/Mn < 1.10), enabling the generation of virtually linear ultrahigh molecular weight polyethylene (UHMWPE, Mw = 6020 kDa) and particularly affording UHMWPE of Mw = 1002 kDa at a high temperature of 90 °C in polar solvents.