Photocatalytically Stable Superhydrophobic and Translucent Coatings Generated from PDMS-Grafted-SiO2/TiO2@PDMS with Multiple Applications

In this paper, we present a highly efficient, cost-effective, and widely applicable functionalized SiO2/TiO2-polymer based coating to fabricate a translucent, fluorine-free, chemically stable, photocatalytic active, self-healable superhydrophobic coating, which consisted of two mixed functionalized particles (MFP) and polydimethylsiloxane (PDMS) in a proper ratio. Both SiO2 and TiO2 powders were functionalized with PDMS brushes to achieve superhydrophobicity. To maximally optimize its properties, including superhydrophobicity, transparency, and photocatalytic activity, the ratios between MFP with PDMS were carefully studied and optimized. Glass slides coated with this mixed coating (MC) showed translucence with a transparency of 75%. It also presented superior photocatalytic activity and strong UV resistance that could repeatedly degrade organic oil pollutants as many as 50 times, while still maintaining superhydrophobicity even upon exposure to UV light with a high intensity of 80 mW/cm2 for as long as 36 h. When low-surface-tension oils such as dodecane wetted the MC surface, it showed excellent slippery performance and could quickly repel strong acid/alkali/hot water and even very corrosive liquids such as aqua regia. MC achieved extremely stable underoil superhydrophobicity (toward liquids including water, strong acid and base, hot water, etc.) and self-cleaning properties, not only in oils at room temperature but also in a scalded oil environment. Moreover, MC showed self-healable performance after recycled plasma treatment. The stainless steel mesh coated with MC was also used to highly efficiently separate oil-water mixtures. Moreover, harsher liquids including strong acid/alkali solutions/hot water/ice water-oil mixtures could also be successfully separated by the coated mesh. This coating was believed to largely broaden both indoor and outdoor applications for superhydrophobic surfaces.