Controlled Orientation of Block Copolymer Microdomains on Modified Solid Surfaces

The interfacial interactions between block copolymers (BCP) and a substrate are important for the self-assembly of BCPs in thin films, especially in terms of orientation of BCP microdomains. A simple, rapid, and robust technique for controlling the alignment of BCP microdomains on modified surfaces is described. End-functionalized poly(styrene-b-ethylene oxide)s (PS-b-PEOs) with different block ratios were end-grafted onto Si substrates creating BCP brushes. Thin films of cylindrical forming PS-b-PEO were prepared on the surface of anchored BCP brushes and thermally annealed. When the fraction of styrene, f, of the anchored BCP was 1, no features were observed in thin film of a PS-b-PEO placed on the surface of the anchored brush due to preferential interaction of the PS block with the brush. When f was varied from 0.3 to 0.7, hexagonally packed cylindrical microdomains oriented normal to the substrate were formed having long range lateral ordering.