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 a o ) were directed to assemble on surfaces chemically patterned with a hexagonal array of spots (interspot spacing a s ). The block copolymer domain assembly was investigated as a function of the film thickness and the commensurability between a o and a s . The domains assembled vertically away from and matched the spacing and hexagonal order of the underlying lithographically patterned chemical substrate, provided a s was equal to or up to 6% larger than a o and the film thickness was ≤54 nm. In contrast, comparably poor assembly was obtained when a s was 8% less than a o . When a s was commensurate with a o, 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.