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

By Satoshi Nakamura, Richard J Archer, Gary J Dunderdale, and Atsushi Hozumi
J. Hazard. Mater.
June 10, 2020
DOI: 10.1016/j.jhazmat.2020.122625

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-Si, CHO-(CHO)-CH-Si(OCH) where n = 3, 6-9, 9-12)-derived hybrid films showing excellent water sliding/removal properties using a simple sol-gel reaction of PEG-Si and tetraethoxysilane (TEOS, Si(OCH)). 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-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-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-Si/TEOS hybrid film surface (1.5 mm/sec, static water CA of ∼40°), in spite of having similar static hydrophilic nature.

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