A method for directing a self-assembly of a block copolymer comprising a first and a second block is provided. The method including: providing a substrate comprising at least one concavity therein, the concavity comprising at least a sidewall and a bottom, the bottom having a preferential wetting affinity for the second block with respect to the first block; grafting a first grafting material onto the sidewall, selectively with respect to the bottom, the first grafting material having a preferential wetting affinity for the first block with respect to the second block; grafting a second grafting material onto the bottom and optionally onto the sidewall, the second grafting material having a preferential wetting affinity towards the first block with respect to the second block; and providing the block copolymer on the substrate, at least within the at least one concavity.