Characterization of Cylinder-Forming Block Copolymers Directed to Assemble on Spotted Chemical Patterns

Films of cylinder-forming polystyrene-block-poly(methyl methacrylate) (bulk intercylinder spacing ao) were directed to assemble on surfaces chemically patterned with a hexagonal array of spots (interspot spacing as). The block copolymer domain assembly was investigated as a function of the film thickness and the commensurability between ao and as. The domains assembled vertically away from and matched the spacing and hexagonal order of the underlying lithographically patterned chemical substrate, provided as was equal to or up to 6% larger than ao and the film thickness was ≤54 nm. In contrast, comparably poor assembly was obtained when as was 8% less than ao. When as was commensurate with ao, the cylinder diameter and eccentricity had a lower standard deviation and was more circular, respectively, than that of self-assembled cylinders on a neutral substrate.