An aqueous coating composition (which optionally can coat plastic substrates) the composition comprising a block copolymer and a polymer P; where the block copolymer comprises at least blocks [A]x[B]y; where at least block [A] is obtained by a controlled radical polymerisation of at least one ethylenically unsaturated monomer via a reversible addition-fragmentation chain transfer (RAFT) mechanism (optionally in solution in the presence of a control agent and a source of free radicals); and wherein block [A] comprises 20 to 100 mol % of ethylenically unsaturated monomer units bearing water-dispersing functional groups; wherein block [B] comprises 20 to 100 mol % of ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups; and wherein polymer P is prepared in the presence of blocks [A]x[B]y. The compositions may be used to coat plastic substrates, foam; surfaces having low surface energy, hydrophobic substrates and/or polyolefins.