Pathway-engineering for highly-aligned block copolymer arrays

• Published in: Nanoscale Vol. 10; no. 1; pp. 416 - 427
• Main Authors: Choo, Youngwoo, Majewski, Paweł W, Fukuto, Masafumi, Osuji, Chinedum O, Yager, Kevin G
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 07.01.2018
• Subjects: Alignment; Block copolymers; Coarsening; Copolymers; Energy conservation; Engine blocks; Metastable state; NANOSCIENCE AND NANOTECHNOLOGY; Self-assembly; Shearing
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c7nr06069f

While the ultimate driving force in self-assembly is energy minimization and the corresponding evolution towards equilibrium, kinetic effects can also play a very strong role. These kinetic effects, such as trapping in metastable states, slow coarsening kinetics, and pathway-dependent assembly, are often viewed as complications to be overcome. Here, we instead exploit these effects to engineer a desired final nano-structure in a block copolymer thin film, by selecting a particular ordering pathway through the self-assembly energy landscape. In particular, we combine photothermal shearing with high-temperature annealing to yield hexagonal arrays of block copolymer cylinders that are aligned in a single prescribed direction over macroscopic sample dimensions. Photothermal shearing is first used to generate a highly-aligned horizontal cylinder state, with subsequent thermal processing used to reorient the morphology to the vertical cylinder state in a templated manner. Finally, we demonstrate the successful transfer of engineered morphologies into inorganic replicas.