Hybrid assembly of nanosol titania and dodecylamine for superhydrophobic self-cleaning glass

This study presents the formation of superhydrophobic films on glass surface resulted from hybrid assembly of inorganic-organic layers based on sol-gel-derived titania (TiO2)/dodecylamine (DDA). One-step and layer-by-layer (LbL) dip-coating approaches are compared and discussed as well as the effect of film annealing rates on the resulting hydrophobicity of glass surfaces. The hydrophobicity was obtained by measuring the water contact angle (WCA) of the films. It is shown that slow annealing rate combined with LbL sol-gel dip-coating produced robust coating with reasonable transparency. The effect of multiple coating and C to Ti mole ratios to the surface hydrophobicity of the resulted films is also reported. As a result, film transparency decreased with increasing coating times. Meanwhile, the C/Ti mole ratios predominantly affect WCA at higher coating numbers. Superhydrophobicity of WCA as high as 155.5° was observed for translucent hybrid film after three-time coating at C/Ti mole ratio of 7. The AFM image confirmed the surface roughness of 78 nm supported with homogeneous interconnected hybrid clusters of TiO 2-DDA over the film surface as shown by the corresponding SEM images. Microhardness tester employing Vickers hardness number (VHN) was used to access the mechanical adhesion of the hybrid films by representing the film retention to scratching. It is observed that VHN increased as the C/Ti mole ratio increased with optimum condition achieving at C/Ti mole ratio of 5 (VHN of 60 kgf/mm2). All films have demonstrated good retention of hydrophobicity for 4 weeks outdoor at high-humidity (RH > 90 %) exposure. This work is expected to pave a way to the creation of transparent superhydrophobic films based on environmentally benign TiO2 inorganic-organic hybrid materials.