Effects of substrate-blocks interactions on the phase behaviors of cylinder-forming block copolymers

Abstract

Self-assembly of block copolymers greatly facilitates production of controlled periodic nanostructures for nanotechnological applications. Orientation control in such structures with defect-free ordering on larger length scales still remain a major research challenge in many cases. In addition to their pure block forms, blends of copolymers with other polymers offer productive research areas in relation to nanostructure self-assembly. We prepared well-aligned nanocylinders in block copolymers over an enhanced sample area and height scale without using any external field applications. Self-assembled 3-dimensional perpendicular cylinder orientation was achieved mainly by blending of minority homopolymer into the block copolymer. In this work, we illustrate that the mixed cylinder nanodomain orientation exits in block copolymer mixtures even with a relatively strong homologous polymer pair interaction and a decreased domain-domain excess free energy, when the interfacial interaction between the majority component and the substrate is high enough to restrict the perpendicular nanodomain orientation. In case of overall perpendicular cylinder-forming block copolymer mixtures, on the other hand, the strong homologous PS pair interaction overcomes the limitation from the relatively high domain-substrate interfacial interactions.