The line/space patterns were then exposed on a Raith EBPG 5200 electron beam lithography system at 100 kV and a 2 nA beam current. The PMMA was then developed using a high contrast cold development process consisting of 7:3 IPA:water at 5 o C ultrasonicated for 100 s. This resulted in arrays of lines with 58 nm (3L0) pitch with line widths of 13-20 nm (0.7L0-1.0L0). The wafer was then dry etched using O2/He plasma to remove the exposed PS brush. The remaining resist was removed with 3 rounds of sonication in NMP for 5 min followed by one round of sonication in chlorobenzene for 5 min to generate the chemical pattern. For the non-preferential brush workflow, the non-preferential PS-r-PMMA-OH brush was used to backfill the exposed Si, followed by application of the BCP film. For the self-brushing workflow, the BCP film was directly applied to the chemical patterns.