Irreversible Physisorption of PS- b -PMMA Copolymers on Substrates for Balanced Interfacial Interactions as a Versatile Surface Modification.

We present a direct approach to fabricating the perfect neutral layer for block copolymer (BCP) self-assembled thin films. An irreversible physisorption of polystyrene- b -poly(methyl methacrylate) (PS- b -PMMA) itself onto the bottom substrates, though extremely thin, offers such a compositional randomness for the substrates, directing the balanced interfacial interactions toward both blocks of the top-layer PS- b -PMMA. Owing to the neutral property from the skin layers, the chemically identical BCP self-assembles into perpendicular microdomains on the adsorbed layer composed of itself, as identified in symmetric PS- b -PMMA films. Intriguingly, the compositional randomness turns out to be valid when the correlation length (ξ) of the BCP layer adsorbed on the substrates is shorter than equilibrium lamellar spacing ( L 0 ) of the BCP. Our strategy provides its versatility applicable to various substrates without any necessity of specific random copolymer brushes or mats, enabling the design of a neutral platform for PS- b -PMMA films.