A process for the preparation polyolefin-based graft copolymers comprising a first long 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, a scavenger, a catalyst or catalyst precursor comprising a metal from Group 3-10 of the IUPAC Periodic Table of elements that can undergo chain transfer polymerization with the main group metal hydrocarbyl functionality of the second type of olefin monomer or that via a chain shuttling agent can undergo 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, a scavenger, a catalyst or catalyst precursor comprising a metal from Group 3-10 of the IUPAC Periodic Table of elements that can undergo chain transfer polymerization with the main group metal hydrocarbyl functionality of the second type of olefin monomer or that via a chain shuttling agent can undergo 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.