The directed self-assembly (DSA) of block copolymers (BCPs) has recently become a viable alternative technique for the nanofabrication of semiconductors. To facilitate pattern transfer onto silicon (Si) wafers from BCP masks, a novel class of Si-rich BCPs with hyperbranched polysiloxane side chains were synthesized in this report. The resistance to oxygen-reactive ion etching (O 2 -RIE) was quantified for the linear and modifiedhyperbranched polysiloxanes, revealing that the modified-hyperbranched polysiloxanes exhibited increased O 2 -RIE resistances. Furthermore, by tailoring the chemical properties on the end-groups of the polysiloxane side chains, atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies revealed that perpendicularly-oriented lamellae could be observed on the thin films.