Light-induced crystallization-driven formation of hierarchically ordered superhydrophobic sol-gel coatings

Nano/micro structures are crucial for superhydrophobic surfaces, but rare are methods able to generate such dual structuring in a single step using a single precursor. We show that the visible light-controlled self-assembly of bis-silylated alkane precursors can create in one-step organosilica coatings exhibiting two levels of hierarchy: lamellae at nanoscale, and plate-like crystals at microscale. Crystallization rate can be precisely controlled by alkylene bridging group and irradiance. This allowed us to achieve superhydrophobic properties by the creation of a dense and uniform network of nanostructured microcrystals with high surface roughness. The obtained coatings displayed chemical stability, good thermal resistance and high mechanical strength through the cross-linked siloxane structure, which is essential for applications.