Abstract: The invention relates to a graft copolymer of the general structure B-(A)nm, consisting of blocks of the two polymers A and B, which have different chemical compositions. One of the polymers is a polycondensation polymer, selected from the group consisting of polycarbonates, polyester carbonates, polyesters, and polyamides, and the other polymer is a polymerisate of at least one vinyl monomer. The invention is characterized in that (i) the average molecular weight of the block of polymer B Mn(B) equals at least 13 kg/mol, determined by a combination of gel permeation chromatography and NMR spectroscopy, (ii) the number of side chains in the graft copolymer ns equals at least 3 and maximally 15, determined by NMR spectroscopy, (iii) the average molecular weight of the block of polymer A Mn(A) equals at least 1.5 kg/mol and maximally 15 kg/mol, determined by a combination of gel permeation chromatography and NMR spectroscopy, and (iv) ns multipled by Mn(A) equals at least 13 kg/mol.