Perfluorinated compounds are not necessary: pegylated organosilanes can endow good water sliding/removal properties

From a viewpoint of reducing the burden on both human health and the environment, alternative surface modification techniques for preparing highly water-repellent surfaces without the use of environmentally damaging perfluorocarbons are highly desirable. Among them, the development of hydrophilic surfaces showing superior water sliding/removal properties has been scarcely reported. In this study, we have successfully demonstrated the fabrication of smooth, transparent, and hydrophilic pegylated organosilanes (PEG_n-Si, CH₃O-(C₂H₄O)_n-C₃H₆-Si(OCH₃)₃ where n = 3, 6-9, 9-12)-derived hybrid films showing excellent water sliding/removal properties using a simple sol-gel reaction of PEG_n-Si and tetraethoxysilane (TEOS, Si(OC₂H₅)₄). The final static/dynamic surface wetting properties of the samples were found to be significantly influenced by both the PEG chain length and their mixing ratios. The use of PEG_n-Si with the longest PEG chain (n = 9-12) was found to be effective for improving water sliding/removal properties. Small volume water droplets (5 μL) on the PEG_9-12-Si/TEOS hybrid film (static water contact angle (CA) of ∼40°) at a 90°-inclined surface could slide at an average speed of 3.4 mm/sec without pinning and tailing, which was about twice as fast as that on the PEG_6-9-Si/TEOS hybrid film surface (1.5 mm/sec, static water CA of ∼40°), in spite of having similar static hydrophilic nature.