Thin Film Morphology of Block Copolymer Blends with Tunable Supramolecular Interactions for Lithographic Applications

A modular and hierarchical self-assembly strategy using block copolymer blends (AB/B’C) with tunable supramolecular interactions is reported. By combining supramolecular assembly of hydrogenbonding units with controlled phase separation of diblock copolymers, highly ordered square arrays or hexagonal arrays of cylindrical domains were obtained formixtures of poly(ethylene oxide)-b-poly(styrene-r4-hydroxystyrene) (PEO-b-P(S-r-4HS)) and poly(styrene-r-4-vinylpyridine)-b-poly(methyl methacrylate) (P(S-r-4VP)-b-PMMA) diblock copolymers under solvent annealing with controlled high humidity. The fraction of the H-bonded phenolic and pyridyl units was shown to be critical for both the generation of longrange order and controlling the spatial arrangement of the cylindrical domains. Both low absolute numbers and a near-stoichiometric ratio of pyridyl-to-phenolic groups are needed to produce ordered square arrays with separated PEO and PMMA domains, whereas a low ratio of pyridyl-to-phenolic groups facilitated the formation of ordered hexagonal arrays with mixed PEO and PMMA domains. Self-consistent field theory simulations suggest that the effective Flory-Huggins parameters between the various blocks control the stability of the different packing structures in this system. The modularity and tunability of this supramolecular block copolymer blending approach is a unique and powerful strategy to fabricate diverse nanostructures for a variety of applications such as block copolymer lithography.