Dr Zhiwei Huang

Superhydrophobic (SH) surfaces with self-cleaning photocatalytic properties have become an important research focus in recent years. In this work, we fabricated multifunctional and environmentally durable SH surfaces via a facile one-step reaction of octadecyl isocyanate (ODI) with TiO2 particles. The resulting films possess SH properties, facilitated by a combination of hydrophobic long alkyl chains and the hierarchical crystalline structure. Films can be prepared via spray or blade coating on a variety of hard and soft substrates, and function well when exposed to either air or oil. The coating retains its SH properties for at least 6 months in ambient conditions, and after organic pollution it can recover its SH properties using UV or sun light illumination. After water impalement, the SH properties can self-heal via the self-assembly of long alkyl chains to their original state within several hours at ambient conditions, or within minutes on a heating stage. The covalent bonds between alkyl chains and TiO2, together with hydrogen bonds between adjacent alkyl chains, greatly increased the surface durability of the SH films. This multifunctional SH coating is a very promising material for commercial and industrial coating

applications.

Maintaining the long-term stability of TiO2-based superhydrophobic (SH) coatings remains a considerable challenge because of the strong photocatalytic properties of TiO2. The organic SH components that surround the TiO2 particles are often degraded when the coating is exposed to UV light, thus destroying the anti-wettability properties. In our work, we fabricated a UV-stable SH coating from dispersions of polydimethylsiloxane (PDMS) and TiO2 nanoparticles, which can be easily applied to a wide range of substrates by spray coating. The resulting films possess SH properties due to the combination of the low surface energy of PDMS, and the hierarchical

structure resulting from the different aggregation sizes of TiO2 nanoparticles. The coating can recover its SH properties after exposure to organic pollutants, which can be photo-degraded and removed by TiO2. The coating is highly durable due to the crosslinked PDMS, and SH properties are retained after 7 days under UV light, or 3 months exposure to sunlight in outdoor conditions. We also demonstrate the coating’s good resistance to corrosion, water impact, and high temperature, all while maintaining superhydrophobicity. This multifunctional SH coating represents a very promising material for commercial and industrial coatings applications.

Durability under UV illumination remains a big challenge of TiO2-based superhydrophobic coatings, with the photocatalytic effect causing degradation of low-surface-energy material over time, resulting in the surfaces losing their hydrophobicity. We report surfaces made from tolylene-2,4-diisocyanate (TDI)/TiO2 hybrid networks that demonstrate superhydrophobicity and superior UV durability. Structural and morphological studies reveal that the TDI/TiO2 hybrid networks are composed of TiO2 nanoparticles interconnected with TDI bridges and then encapsulated by a TDI layer. Through controlling the fraction of TDI in the synthesis process, the thickness of the TDI encapsulation layer around the TDI/TiO2 hybrid networks can be varied. When the weight ratio of TDI/TiO2 is 5:1, the superhydrophobicity of the hybrid network surface remains almost unchanged after a month of continuous UV illumination. This hybrid network surface can also clean methylene blue solution through the synergistic effects of cation adsorption and photocatalysis, holding promising potential for applications toward reducing cation pollutions in both liquid and air environments.