We illustrate that the redistribution of a compatible homopolymer blended in a certain block copolymer results in a shift of phase boundaries and in the stabilization of well-ordered structures by using polystyrene (PS) homopolymer blended in polystyrenepolybutadiene- polystyrene triblock copolymer (SBS1102) as a model system. The addition of the homopolymer into the asymmetric triblock copolymer increases the periodic orientation normal to the substrate, enabling directed self-assembly of the block copolymers into arrays of highly oriented, high-aspect-ratio cylindrical nanostructures over large areas. Thus, we show that blending a homopolymer with well controlled molecular weight provides an effective ordering process for self-assembly of block copolymers.