A method for functionalising a substrate intended for the self-assembly of a block copolymer, includes depositing on the surface of a substrate a layer of a first polymer material, the first polymer having a first chemical affinity with respect to the block copolymer; grafting one part only of the first polymer material layer onto the surface of the substrate; printing, using a mould, patterns in a sacrificial layer arranged above the grafted part of the first polymer material layer; transferring the patterns of the sacrificial layer into the grafted part of the first polymer material layer, until the substrate is reached; and removing at least one part of the sacrificial layer by wet etching, so as to uncover the grafted part of the first polymer material layer.