Trilayered Block Copolymer Nanostructures Formed by an Iterative Layering Strategy

Abstract Nanostructured block copolymer (BCP) thin films enable the formation on‐demand of a variety of periodic patterns at the nanometer scale by tuning the macromolecular BCP characteristics and annealing processes. Significant progress in the control of the self‐assembly has been witnessed over the past decade with the implementation of robust directed self‐assembly methods. However, the self‐assembled structural patterns obtained at equilibrium are limited and methods to expand the range of structural configurations are required to harness additional functionalities. Here, this work demonstrates how polystyrene‐b‐poly(methyl methacrylate) BCP thin layers can be stacked to produce a library of complex 3D hierarchical heterostructures. In this iterative assembly process based on simple building bricks (i.e., immobilized BCP patterns forming Holes, Lines and Dots), the stacking configuration (i.e., self‐assembly and registration) of a BCP thin film is directed with respect to the previous layer using confinement effects and interfacial energy tuning. This responsive layering can lead to intricate 3D Al₂O₃ structures and opens the way to a broad variety of structural designs toward functional applications.