Directed assembly of high molecular weight block copolymers: Highly ordered line patterns of perpendicularly oriented lamellae with large periods

The directed assembly of block copolymer nanostructures with large periods exceeding 100 nm remains challenging because the translational ordering of long-chained block copolymer is hindered by its very low chain mobility. Using a solvent-vapor annealing process with a neutral solvent, which was sequentially combined with a thermal annealing process, we demonstrate the rapid evolution of a perpendicularly oriented lamellar morphology in high molecular weight block copolymer films on neutral substrate. The synergy with the topographically patterned substrate facilitated unidirectionally structural development of ultrahigh molecular weight block copolymer thin films - even for the structures with a large period of 200 nm - leading to perfectly guided, parallel, and highly ordered line-arrays of perpendicularly oriented lamellae in the trenched confinement. This breakthrough strategy, which is applicable to nanolithographic pattern transfer to target substrates, can be a simple and efficient route to satisfy the demand for block copolymer assemblies with larger feature sizes on hundreds of nanometers scale.