Formation of Hierarchically Structured Thin Films

Here, we report the preparation of hierarchically structured polymer brushes with well-defined geometries via multiple step microcontact printing (MS-mu CP) of inks containing different ratios of initiator-terminated thiols and non-reactive alkylthiols. Thick (and dense), polymer brushes grew from self-assembled monolayers (SAMs) with high concentration of initiator-terminated thiols, and these brushes exhibited high chemical etch-resistance, compared to thin (and less dense), brushes grown from more dilute initiator-terminated SAMs. Upon etching, patterned crosslinking polymer brush films decorated with thin layers of Au, could be lifted off the surface to form geometrically well-defined free-standing hierarchical films. These polymer brush films showed interesting buckling instabilities when compressed. Areas with different brush thicknesses and Au backing showed markedly different buckling behavior, leading to unusual patterns of wrinkles with different wavelengths and orientations toward the force field.