The invention relates to the field of block copolymers, particularly to the field of water-soluble or water-dispersible copolymers consisting of two blocks, of which the major block is a hydrophilic thermoplastic block. More particularly, the invention relates to a block copolymer consisting of a partially or totally hydrophilic elastomeric block, with a Tg of less than 30° C. and comprising at least one hydrophilic monomer, and a water-soluble thermoplastic block with a Tg of greater than 30° C. and comprising at least one monomer bearing a carboxyl group, said copolymer being partially or totally soluble in water or in aqueous medium, and the mass proportion of the thermoplastic block being greater than 50% of the weight of said copolymer.