A graft copolymer comprising polyolefin and engineering thermoplastic components, wherein the thermoplastic component is a polymer comprising heteroatoms or heteroatom containing moieties in its backbone and phenyl or substituted phenyl groups, the polyolefin component covalently bound to the engineering thermoplastic component. The graft copolymer is the reaction product of an engineering thermoplastic having at least one phenylene in the polymer backbone, and a vinyl/vinylidene terminated polyolefin having a weight average molecular weight of at least 300 g/mole, wherein the vinyl/vinylidene terminated polyolefin is selected from polyethylenes, polypropylenes, ethylene-propylene copolymers, polyisobutylenes, polydienes, propylene-based elastomers, ethylene-based plastomers, and combinations thereof.