A functionalized block copolymer comprising: (a) at least one end block D comprising at least one amino-functionalized polymer unit of formula and one or more additional blocks selected from the group consisting of: (b) one or more A blocks substantially free of amino-functional groups and having a number average molecular weight of from 1,000 to 60,000, and has an upper limit of the service temperature of at least 20°C, wherein substantially free of amino-functional groups means that the A blocks comprise on average less than 1 polymer unit which carries a substituent comprising the moiety -ZR 2 with Z being nitrogen, wherein the number average molecular weight is measured with gel permeation chromatography using a polystyrene calibration standard according to ASTM D5296, and wherein the upper limit of the service temperature is the glass-transition temperature, if the A blocks are glassy polymer blocks, or the melting temperature, if the A blocks are crystalline or semi-crystalline polymer blocks, and (c) one or more B blocks, wherein each block B is essentially non-functionalized, has a number average molecular weight of from 1,000 to 1,000,000, and has a glass transition temperature of at most 20°C, wherein essentially non-functionalized means that the B blocks comprise on average less than 1 polymer unit which carries a substituent comprising the moiety - ZR 2 with Z being nitrogen, and wherein the number average molecular weight is measured with gel permeation chromatography using a polystyrene calibration standard according to ASTM D5296, the glass-transition temperature and the melting temperature are determined using differential scanning calorimetry, and (d) mixtures of one or more A blocks and one or more B blocks; wherein Z is nitrogen; R 1 is hydrogen or alkyl; R 2 is hydrogen or is tertiary alkyl; and two R groups, together with the Z to which they are bonded, form an optionally substituted ring; wherein 10 to 100 % of the functional groups of the block(s) D are in the form of a corresponding onium salt, wherein the D block is formed on each of the external ends of the block copolymer, wherein the D block is formed from amino functional monomer prior to polymerization reaction, and wherein the functionalized block copolymer comprises at least one B block, wherein the at least one B blocks together are at least 75 wt % of the molecular weight of the block copolymer, and wherein the block copolymer is star-branched. (a) at least one end block D comprising at least one amino-functionalized polymer unit of formula and (b) one or more A blocks substantially free of amino-functional groups and having a number average molecular weight of from 1,000 to 60,000, and has an upper limit of the service temperature of at least 20°C, wherein substantially free of amino-functional groups means that the A blocks comprise on average less than 1 polymer unit which carries a substituent comprising the moiety -ZR 2 with Z being nitrogen, wherein the number average molecular weight is measured with gel permeation chromatography using a polystyrene calibration standard according to ASTM D5296, and wherein the upper limit of the service temperature is the glass-transition temperature, if the A blocks are glassy polymer blocks, or the melting temperature, if the A blocks are crystalline or semi-crystalline polymer blocks, and (c) one or more B blocks, wherein each block B is essentially non-functionalized, has a number average molecular weight of from 1,000 to 1,000,000, and has a glass transition temperature of at most 20°C, wherein essentially non-functionalized means that the B blocks comprise on average less than 1 polymer unit which carries a substituent comprising the moiety - ZR 2 with Z being nitrogen, and wherein the number average molecular weight is measured with gel permeation chromatography using a polystyrene calibration standard according to ASTM D5296, the glass-transition temperature and the melting temperature are determined using differential scanning calorimetry, and (d) mixtures of one or more A blocks and one or more B blocks; Z is nitrogen; R 1 is hydrogen or alkyl; R 2 is hydrogen or is tertiary alkyl; and two R groups, together with the Z to which they are bonded, form an optionally substituted ring;