Crafting positive/negative patterns and nanopillars of polymer brushes by photocatalytic lithography

We demonstrate a convenient and versatile approach based on the photocatalytic lithography to obtain micro- and nanostructures of polymer brushes. Micro-patterns of polymer brushes are obtained through two ways: by the selective photocatalytic degradation of an initiator, self-assembled on the surface (“positive” pattern), or by a “negative” pattern obtained, first, degrading an alkylsiloxane monolayer and, then, refilling it with the initiator. In both cases, the patterned initiator monolayer is eventually amplified into polymer brushes with a controlled radical polymerization protocol (ARGET ATRP). The approach described here mimics the conventional photolithography but is free from the disadvantages associated to this technique (i.e. highly energetic light sources, polymeric resists and on purpose-made photomasks). Moreover, the ability to generate nanometer-sized pillars of polymer brushes using remote photocatalysis coupled with nanosphere lithography is demonstrated. Highly monodisperse silica particles with spherical shape (diameter ∼600 nm) are assembled on the surface to be patterned and used as a mask for remote photocatalysis. Our results confirm the great potentialities of TiO2-photocatalytic lithography for patterning of polymer brushes.