Long-range ordering of diblock copolymers induced by droplet pinning

The directed self-assembly of diblock copolymers offers unique routes for the design and fabrication of well-ordered arrays of nanoscopic structures. However, generating arrays with long-range order and few defects has been a difficult goal to achieve without extended thermal annealing processes. Here, a simple, one-step route, based on the flow of a solution within a droplet pinned to a surface coupled with solvent evaporation, is shown where highly oriented, ordered arrays of nanoscopic cylindrical domains of a block copolymer can be produced over large distances (tens of microns). Hexagonal arrays of the cylindrical domains of block copolymers are shown to orient parallel to the film surface and in the direction of an evaporation-induced flow, producing morphologies with very long-range order. This solution casting process, that naturally couples two orthogonal fields, is easily transferable to blade- and dip-coating processes that are routinely used to prepare thin films. Thus, a simple route is shown, by which the barrier to long-range order in arrays of nanoscopic elements can be overcome, providing valuable insight for designing addressable media.