The present invention relates to a method for preparing a polymer composition, said method comprising the steps of: a) preparing a reaction mixture comprising as component A) an ethylenically unsaturated monomer or a mixture of ethylenically unsaturated monomers and as component B) a 1-alkene or a mixture of 1-alkenes; b) adding a Co(ll) complex as a catalytic chain transfer agent to the reaction mixture; c) adding a radical initiator; and d) reacting the reaction mixture to obtain the polymer composition, wherein the total amount of the radical initiator added to the reaction mixture is at least 0.05% by weight relative to the total weight of components A) and B). The present invention also relates to the use of a Co(ll) complex as catalytic chain transfer agent for the polymerization of a reaction mixture comprising an ethylenically unsaturated monomer or a mixture of ethylenically unsaturated monomers, a radical initiator, and a 1-alkene or a mixture of 1-alkenes, wherein the total amount of the radical initiator added to the reaction mixture is at least 0.05% by weight relative to the total weight of the ethylenically unsaturated monomer or mixture of ethylenically unsaturated monomers and the 1-alkene or mixture of 1-alkenes.