Superhydrophobic and low-hysteresis coating based on rubber-modified TiO₂/SiO₂ nanoparticles

In this article, the wettability of a superhydrophobic layer from rubber-modified TiO₂/SiO₂ nanocomposite is studied. The nanocomposites were prepared with various ratios of TiO₂ and SiO₂ nanoparticles (NPs) and then studied the effect of annealing, UV irradiation and aging after coating on a substrate. Results show that the average contact angle of deionized water droplets on the most hydrophobic coating is 129.5°, which increases up to 151.0° by UV irradiation. In addition, the lowest surface energy of the prepared layers was measured as 29.61 mJ m^–2. The hydrophobicity of the coating surface was investigated after annealing (at temperatures up to 300°C), and results show that the maximum contact angle is about 150°. The dynamics of water droplets on the most hydrophobic coating were investigated by rapid imaging, and results show no hysteresis for surface wetting. Fourier transform infrared spectroscopy shows that UV irradiation causes the formation of C–H functional groups on the surface without considerable change in the hydrophobicity, while the annealing process has no significant effects on the functional groups. The morphology of the coatings was investigated by scanning electron microscopy, and results reveal that the roughness of surfaces increases due to annealing and UV radiation. In addition, a minimum increase in the roughness coefficient is estimated as 73% of the initial value after annealing, which is in agreement with atomic force microscopy results.