Rapid Assembly of Nano lines with Precisely Controlled Spacing from Binary Blends of Block Copolymers

Thin films cast from binary blends of structurally homologous polystyrene-block-poly(2-vinylpyridine) polymers were used to obtain horizontal arrays of linear nanostructures which were visualized by metallizing the poly(2-vinylpyridine) blocks with a tetrachloroplatinate salt. By varying the blend compositions of the homologous block copolymers, fine control over the periodicity of lines was realized from similar to 25 to 55 nm using a set of just 4 block copolymers. For neat block copolymers whose equilibrium structures are not horizontal cylinders, blending enabled cylindrical structures to form. The ordering in various films was studied by measurements of defect density, and it was found that in many cases blended films produced patterns of lower defect density than patterns formed from single component block copolymers. Annealing of the polymer films was carried out using a solvothermal microwave annealing technique able to rapidly produce few-defect films. Here the technique is adapted to use a household microwave oven (cost < $100) to rapidly induce self-assembly in under 2 min, enabling broad accessibility.