Self-Organized Hierarchical Structures in Polymer Surfaces: Self-Assembled Nanostructures within Breath Figures

Herein we report the preparation of hierarchically micro- and nanostructured polymer surfaces in block copolymer/homopolymer blends. The structural order at different length scales was obtained combining two methodologies, e.g., the breath figures method to produce porous microstructures (top-down approach) with block copolymer self-assembly to induce microphase separation at the nanometer length scale (bottom-up approach). The interplay of the breath figure formation during the spin-coating and self-assembly of the triblock copolymer allowed the preparation of polymer surfaces having micrometer-sized cavities decorated with nanostructured block copolymers. The system described herein possesses unique characteristics. First, the surface chemical composition can be varied by a surface rearrangement upon annealing either to dry or humid air. Moreover, surface rearrangement is accompanied with structural changes, i.e. both topography and nanostructuration can be reversibly modified upon annealing. In terms of topograghy, a transition between holes and hills was obtained upon soft annealing to water vapor and can be recovered upon annealing to dry air. Finally, the pore nanostructure can be modulated from a micellar array to a lamellar phase when the film is exposed either to air or to tetrahydrofuran vapor.