Facile Synthesis of High-Molecular-Weight Vinyl Sulfone (Sulfoxide) Modified Polyethylenes via Coordination-Insertion Copolymerization

Vinyl sulfones or sulfoxides are problematic monomers to polymerize via any polymerization mechanism. In this contribution, a comprehensive picture of ethylene/vinyl sulfone (sulfoxide) copolymerization was investigated carefully by using phosphino-phenolate nickel catalysts. A stoichiometric study revealed that vinyl sulfone (sulfoxide) preferred 2,1-insertion into Ni-CH3 following pseudo-first-order kinetics. Furthermore, the nickel catalyst exhibited a high activity (ca. 23000 g(PE) mol(Ni)(-1) h(-1)) for ethylene/vinyl sulfone copolymerization and produced very high-molecular-weight (M-w 78500) copolymers with relatively high incorporations of 6.1 mol % under mild conditions. More importantly, the polar monomer could selectively insert into the polymer main chain rather than locate at the chain end. These resultant copolymers kept excellent crystallinity with high melting temperatures and displayed greatly improved surface properties. By contrast, a typical alpha-diimine palladium catalyst showed no activity toward this copolymerization; the phosphine benzenesulfonate palladium catalyst produced lower-molecular-weight copolymers (M-w ca. 3100). That is, bulky phosphino-phenolate nickel was a promising catalyst to produce linear high-molecularweight sulfone- or sulfoxide-modified polyethylenes with high selectivity.