Sequence-Encoded Perpendicular Orientation in High-χ Triblock Copolymer Thin Films via Central Hydrophobic Block Placement

Block copolymer lithography is a promising technique for nanoscale patterning in semiconductor manufacturing, where perpendicular domain orientation is essential. This study elucidates the influence of hydrophobic block position within triblock copolymers on the formation of well-ordered perpendicular orientation. Triblock copolymers with hydrophobic blocks precisely positioned at the middle and terminal are synthesized via living anionic polymerization and efficient thiol-epoxy reactions. Atomic force microscopy (AFM) reveals that perpendicular microdomain orientation is achieved only when the low-surface-energy block is placed centrally, where chain connectivity frustrates complete surface segregation and thereby stabilizes a perpendicular lamellar orientation. Further analyses via cross-sectional scanning electron microscopy (SEM) and grazing incidence small-angle X-ray scattering (GI-SAXS) demonstrate the perpendicular orientation across the entire film. These findings provide design guidelines for high-χ block copolymers enabling perpendicular orientation for nanolithography.