Positive Effect of Polar Solvents in Olefin Polymerization Catalysis
Chaoqun Wang, Xiaohui Kang, Hongliang Mu, Zhongbao Jian
Abstract
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.