Synthesis of polyethylene-g-polystyrene and polyethylene-g-poly(p-methylstyrene) graft copolymers

This paper describes a new method to prepare polyethylene graft copolymers, such as polyethylene-g-polystyrene and polyethylene-g-poly(p-methylstyrene), with a relatively well-controlled reaction mechanism. The chemistry involves a transformation process from the metallocene copolymerization of ethylene and p-methylstyrene to the anionic living polymerization of styrene or p-methylstyrene. The metallocene catalysis produces poly(ethylene-co-p-methylstyrene) random copolymers with molecular weight distribution (M̄_w/M̄_n of about 2.5. The following selective metalation reaction of p-methylstyrene units in the copolymer and the subsequent anionic "living" graft-from polymerization were effective to produce polymeric side chains with well-defined structure. Both graft density and graft length can be controlled by p-methylstyrene content in the PE backbone, metalation reagent, and the quantity of monomer used in the graft-from reaction. In the bulk, the individual PE and PS segmente in the graft copolymers are phases-seperated to form crystalline PE domains and amorphous PS domains. The microscopy studies reveal the effectiveness of PE-g-PS in the polymer blends by reducing the phase sizes, improving the dispersion, and increasing interfacial interaction between domains.