Nanoscopic surface patterns from functional ABC triblock copolymers

We synthesized analogous series of monodisperse ABC triblock copolymers with symmetrical end blocks A/C and different short middle blocks B (5-10 wt %) with varying polarities by sequential anionic polymerization, i.e., polystyrene-b-poly(2-vinylpyridine)-b-poly(methyl methaerylate) (PS-b-P2VPb-PMMA) and polystyrene-b-poly(2-hydroxyethyl methaerylate)-b-poly(methyl methacrylate) (PS-b-PHEMA-b-PMMA). Thin (thickness similar to 20 nm) and ultrathin films (thickness less than or equal to 7 nm) were prepared by either dip-coating or adsorption from solution onto silicon wafers. The copolymer films were investigated by scanning force microscopy. In thin films, the polar middle block adsorbs preferentially to the polar substrate, resulting in a polymer film surface that exclusively consists of PS and PMMA microdomains. In ultrathin films, the two polar B and C blocks behave like a single B block resulting in structures which can be described by recent scaling laws. The lateral spacing and the morphology of the structures can be controlled by film thickness and A/C block length.