Design and characterization of multicolor water-repellent coatings: Impact of alkyl chain length on surface properties

Fabrication of functional colored water-repellent surfaces is very important for many industrial applications. Here, various colorful surface coating materials having water repellent property, chemical, thermal and UV light resistance and self-cleaning property were prepared using activated halloysite nanotube loaded with dye (A-Hal/ dye), different alkoxysilanes (methyltriethoxysilane (MTES), octyltriethoxysilane (OTES) and hexadecyltrimethoxysilane (HDTMS)), and tetraethoxysilane and their coatings were performed on various substrates to determine the effect of alkyl chain length of alkoxysilane compound used in the coating formulation on the surface properties of colorful surfaces. Characterization studies of the synthesized surfaces or coated materials were performed using electron microscopy (TEM and SEM), SEM-mapping, FTIR, XRD, XPS and thermal gravimetic analysis techniques. Water contact angle (WCA) of glass surfaces coated with A-Hal/MB/MTES, AHal/MB/OTES and A-Hal/MB/HDTMS materials was found to be 148.0, 156.2 and 159.3 degrees, respectively. The use of an alkoxysilane compound with long functional alkyl chain group in the coating formulation improved the water-repellent property of surface, while it slightly weakened the mechanical stability of the colorful surface. Polydimethylsiloxane (PDMS) coating, which were applied on colorful surfaces, improved the mechanical, thermal, chemical and environmental stability of coating, but decreased the water-repellent property of coated colorful surfaces. Fabricated coating materials having different colors were successfully used to coat various substrates such as glass, filter paper, wood, and cotton fabric. The results of this study show that A-Hal/dye/ HDTMS coating materials prepared here are of a great potential in the fabrication of functional surface coatings.