A process for the preparation polyolefin-based graft copolymers comprising a first short chain branched polyolefin block and one or multiple polymer side chains, said process comprising the step of: A) a polymerization step comprising copolymerizing at least one first type of olefin monomer and at least one second type of olefin monomer comprising a main group metal hydrocarbyl functionality according to Formula 1a: R 100 (n-2) R 101 M n+ R 102 using a catalyst system to obtain a polyolefin; wherein said catalyst system comprises a co-catalyst and/or a scavenger and a catalyst or catalyst precursor comprising a metal from Group 3-10 of the IUPAC Periodic Table of elements that does not lead to chain transfer polymerization with the main group metal hydrocarbyl functionality of the second type of olefin monomer, and wherein further M is a main group metal; n is the oxidation state of M; R 100, R 101 and R 102 of Formula 1a are each independently selected from the group consisting of a hydride, a C1-C18 hydrocarbyl group, or a hydrocarbyl group Q on the proviso that at least one of R 100, R 101 and R 102 is a hydrocarbyl group Q, wherein hydrocarbyl group Q is according to Formula 1b: wherein Z is bonded to M and Z is a C1-C18 hydrocarbyl group; R 105 optionally forms a cyclic group with Z; wherein R 103 and R 104 and R 105 are each independently selected from hydrogen or a hydrocarbyl group; and at least one of the steps of: B) an oxidizing step comprising contacting said polyolefin obtained in step with at least one oxidizing agent to obtain a polyolefin having one or more pending oxidized functionalities; and/or C) contacting said polyolefin obtained in step B) with at least one quenching agent to obtain a polyolefin having one or more pending polar functionalities, D) using the polyolefin having one or more pending polar functionalities obtained in step C) to obtain a graft copolymer by transesterification of a preformed transesterifiable polymer and/or by ring-opening polymerization of cyclic monomers. A) a polymerization step comprising copolymerizing at least one first type of olefin monomer and at least one second type of olefin monomer comprising a main group metal hydrocarbyl functionality according to Formula 1a: R 100 (n-2) R 101 M n+ R 102 using a catalyst system to obtain a polyolefin; wherein said catalyst system comprises a co-catalyst and/or a scavenger and a catalyst or catalyst precursor comprising a metal from Group 3-10 of the IUPAC Periodic Table of elements that does not lead to chain transfer polymerization with the main group metal hydrocarbyl functionality of the second type of olefin monomer, and wherein further M is a main group metal; n is the oxidation state of M; R 100, R 101 and R 102 of Formula 1a are each independently selected from the group consisting of a hydride, a C1-C18 hydrocarbyl group, or a hydrocarbyl group Q on the proviso that at least one of R 100, R 101 and R 102 is a hydrocarbyl group Q, wherein hydrocarbyl group Q is according to Formula 1b: wherein Z is bonded to M and Z is a C1-C18 hydrocarbyl group; R 105 optionally forms a cyclic group with Z; wherein R 103 and R 104 and R 105 are each independently selected from hydrogen or a hydrocarbyl group; and at least one of the steps of: B) an oxidizing step comprising contacting said polyolefin obtained in step with at least one oxidizing agent to obtain a polyolefin having one or more pending oxidized functionalities; and/or C) contacting said polyolefin obtained in step B) with at least one quenching agent to obtain a polyolefin having one or more pending polar functionalities, D) using the polyolefin having one or more pending polar functionalities obtained in step C) to obtain a graft copolymer by transesterification of a preformed transesterifiable polymer and/or by ring-opening polymerization of cyclic monomers. B) an oxidizing step comprising contacting said polyolefin obtained in step with at least one oxidizing agent to obtain a polyolefin having one or more pending oxidized functionalities; and/or C) contacting said polyolefin obtained in step B) with at least one quenching agent to obtain a polyolefin having one or more pending polar functionalities, D) using the polyolefin having one or more pending polar functionalities obtained in step C) to obtain a graft copolymer by transesterification of a preformed transesterifiable polymer and/or by ring-opening polymerization of cyclic monomers.