The self-assembly of a lamellar-forming polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) diblock copolymer (DBCP) was studied herein for surface nanopatterning. The DBCP was synthesized by sequential living anionic polymerization of styrene and hexamethylcyclotrisiloxane (D₃). The number average molecular weight (M_n), polydispersity index (M_w/M_n) and PS volume fraction (φ_ps) of the DBCP were M_n^PS = 23.0 kg mol⁻¹, M_n^PDMS = 15.0 kg mol⁻¹, M_w/M_n = 1.06 and φ_ps = 0.6. Thin films of the DBCP were cast and solvent annealed on topographically patterned polyhedral oligomeric silsesquioxane (POSS) substrates. The lamellae repeat distance or pitch (λ_L) and the width of the PDMS features (d_L) are ~35 nm and ~17 nm, respectively, as determined by SEM. The chemistry of the POSS substrates was tuned, and the effects on the self-assembly of the DBCP noted. The PDMS nanopatterns were used as etching mask in order to transfer the DBCP pattern to underlying silicon substrate by a complex plasma etch process yielding sub-15 nm silicon features.