Directed self-assembly (DSA) of block copolymers (BCPs) is an effective approach for the fabrication of sub-10 nm features for semiconductor devices. Although many high-χ BCPs have been developed for DSA, the majority of them has a significant difference in surface energies (γs) between two blocks. Here we report the synthesis and self-assembly of poly (styrene-b-vinyl acetate) (PS-b-PVAc). PS-b-PVAc has a higher Flory-Huggins interaction parameter (χ) than poly (styrene-b-methyl methacrylate) (PS-b-PMMA) and the smallest achievable period (L_O) is 18.2 nm. PS and PVAc have nearly equal γs and a perpendicular orientation of domains is obtained on random copolymer brushes under thermal annealing. DSA of PS-b-PVAc (SV-1 and SV-2) is successfully demonstrated in the thin films on chemical patterns, and the feature size down to 9.5 nm is obtained in DSA of SV-4 with 2 × density multiplication. These results demonstrate that PS-b-PVAc could be a candidate BCP for next-generation DSA lithography.