The present invention relates to a process for the preparation of polyolefin-based graft copolymers comprising a first functionalized short chain branched polyolefin block and one or multiple polymer side chains. The functionalized short chain branched polyolefin is produced via the copolymerization of an olefin monomer and an olefin bearing a main group metal hydrocarbyl functionality. Subsequently the graft copolymers according to the invention can be produced for example by ring-opening polymerization of cyclic monomers or by transesterification of a preformed transesterifiable polymer, especially polyesters or polycarbonates. The invention moreover relates to polyolefin-based graft copolymers obtained by said process.