Robust and Highly Transparent Photocurable Fluorinated Polyurethane Coating Prepared via Thiol-Click Reactions and What Essentially Influences Omniphobic Coating’s Anti-Graffiti Properties

Abstract

Without a fragile micro/nanostructure, omniphobic coatings have a natural advantage over superomniphobic coatings in mechanical durability, especially when confronted with finger wipes and squeezes in practical use. Many reported omniphobic coatings with lower liquid sliding angles showed better ink trace resistance. However, according to our results, these two properties are not positively related. The respective critical factors for lowering the liquid sliding angle and resisting tiny contaminants, such as ink stroke and fingerprint, remain elusive. Through three steps of the thiol-click reaction, a surface-dried, highly transparent, mechanically and chemically robust, fluorinated polyurethane coating was photocured efficiently. Surfaces that exhibited better sliding performance but worse resistance to ink stroke and fingerprint were reported. Our results indicate that a heavy cross-linked structure was beneficial for the resistance to tiny contaminants, while the liquid sliding performance only depended on the surface fluorine content, especially the surface enrichment of flexible low-surface-tension chains. Interestingly, an unexpected transformation from a turbid dispersion to a transparent solution during the preparation was observed. The efficient thiol-click reaction induces a micelle-like structure to open and imparts high transparency to the final coatings. Therefore, this work provides useful information to facilitate the study of omniphobic coatings, as well as a good candidate in anti-graffiti applications.