The present invention relates to a novel block copolymer of structure 1, wherein, A- is a block polymer chain, B is a block polymer chain, wherein, A- and B- are chemically different, covalently connected polymer chains, which are phase separable and the moiety X(Y(Z)b)a is a junction group, which comprises a surface active pendant moiety Y(Z)b wherein: a is an integer from 1 to 4 denoting the number of surface active pendant moieties Y(Z)b on X, b is an integer from 1 to 5 denoting the number of Z moieties on the linking moiety Y, X is a linking group between the A polymer block, the B polymer block and the moiety Y, Y is a linking group or a direct valence bond between X and Z; and Z is a moiety independently selected from, a fluorine containing moiety, a Si1-Si8 siloxane containing moiety or a hydrocarbon moiety with at least 18 carbons, and further wherein the junction group X(Y(Z)b)a has a surface energy less than that that of the block A and less than that of the block B. The invention also relates to a composition comprising the novel copolymer and its use in direct self-assembly processes.