Air-Water Interfacial Directed Self-Assembly of Block Copolymer Nanostrand Array

Interfacial self-assembly (ISA) of block copolymers (BCPs) creates various periodic 2D nanostructures at the air-water interface, such as dot, strand, and planar morphologies, which are widely used in various applications. Here, a directed self-assembly strategy to control the pattern direction of ISA of strand morphology, so-called nanostrands, in a large area using a gradual morphology transition is introduced. ISA of BCPs in a lens-shaped droplet of a concentrated BCP solution at the air-water interface shows the gradual morphology transition from the edge to the center of the droplet. The gradual morphology transition is explained by the spreading area-dependent dewetting mechanism. Furthermore, a dense nanostrand array in a large area which is highly aligned normal to the radial direction of the droplet at an intermediate transition regime is found. In addition, a density-doubled metal nanowire fabrication and a hierarchical BCP nanopatterning by using the highly aligned nanostrand array as a template are demonstrated.