Orienting Block Copolymer Microdomains with Block Copolymer Brushes

A simple, rapid, and robust technique for controlling the self-assembly of block copolymers (BCPs) with a large segmental interaction parameter, χ, is described using a surface modified with anchored BCP brushes. End-functionalized poly(styrene-b-ethylene oxide)s (PS-b-PEOs), where the fraction of PS (f_PS) was varied, end-functionalized neat PS, and end-functionalized neat PEO were end-grafted onto Si substrates modifying the surface with polymer brushes. Thin films of cylinder-forming PS-b-PEO were prepared on modified Si substrates and thermally annealed. When neat PS and PEO were used as the anchored brushes, the microdomains of the PS-b-PEO oriented parallel to the substrate upon thermal annealing due to the preferential interactions of one block to the anchored brushes. However, when end-functionalized PS-b-PEOs were used to modify the substrate, hexagonally packed cylindrical PEO microdomains oriented normal to the substrate, having long-range lateral ordering, were obtained over a very wide range of f_PS (0.32 to 0.77).