This invention relates to a graft copolymer comprising: a) a macromonomer, wherein the macromonomer comprises in polymerized form a first monoethylenically unsaturated monomer selected from a group consisting of esters of methacrylic acid and acrylic acid with straight or branched alcohols having 1 to 3 carbon atoms and no more than 5 mole % an addition fragmentation chain transfer agent; and b) at least one side chain on the macromonomer, wherein the at least one side chain comprises at least 95 wt.-% of acrylic acid in polymerized form, and its use for improving the dirt pick-up resistance of a paint or coating.