Block copolymer, process to synthesize it, composition and article made therefrom

Block copolymer comprising:at least one block of a polymer comprising at least 50 mole % of recurring units (R1) formed by the polycondensation reaction between at least one aromatic dihalocompound comprising at least one -S(=O)2- group and at least two aromatic rings, and at least two aromatic diols, at least one aromatic diol (D1) comprising only one aromatic ring and at least one other aromatic diol (D2) comprising at least two aromatic rings [block (A)], andat least one block of a polymer comprising at least 50 mole % of recurring units (R2) formed by the polyaddition of at least one alkylene oxide [block (B)]. Process to synthesize said block copolymer. Polymer composition comprising said block copolymer. Article, in particular membrane, comprising said block copolymer or said polymer composition. Use of said membrane for purifying a liquid.