Fabrication of high performance superhydrophobic coatings by spray-coating of polysiloxane modified halloysite nanotubes

- Halloysite nanotubes (HNTs) were treated by n-hexadecyltriethoxylsilane and tetraethoxysilane.
- Superhydrophobic coating was fabricated by spray-coating polysiloxane modified HNTs.
- Silane affects transparency, morphology, and superhydrophobicity of HNTs coating.
- HNTs coatings exhibit super self-cleaning and oil/water separation functions.

Superhydrophobic coatings with high water contact angles, ultralow sliding angles, excellent stability, oil/water separation, and self-cleaning functions were fabricated by spray-coating the suspensions of polysiloxane modified halloysite nanotubes (POS@HNTs) onto various substrates. The hydrophobic treatment of HNTs was performed by hydrolytic co-condensation of n-hexadecyltriethoxylsilane and tetraethoxysilane on the surfaces of the HNTs. A thick POS layer is located on the surfaces of the HNTs, which makes HNTs hydrophobic. The POS@HNTs were characterized using scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy and thermogravimetric analysis. The effects of the ratio of silane and HNTs on the transparency, morphology, and wettability of the coatings were investigated. The transparency of the coating decreases with the increase in the silane loading. The water contact angles of the POS@HNTs coating increase with the increase in the silane loading, but the water sliding angles of the coatings are nearly independent on their ratio. The stability, oil/water separation, and self-healing capability of the coatings were also studied. The coatings on different substrates show high contact angle towards different liquid, e.g. 1 M HCl, 1 M NaOH, tea, and milk. Also, the POS@HNTs coated meshes can efficiently separate oils from water with high separation efficiency. In addition, the POS@HNTs coated gloves show a self-cleaning effect. All these results suggest that the POS@HNTs exhibit great potential for their application in waterproof materials, self-cleaning coating, and oil/water separation devices.

Schematic illustration for the synthesis of the POS@HNTs and the superhydrophobic POS@HNTs surfaces fabricated by spray-coating (the blue-colored globule represents water droplet on the surfaces).75