PDMS-Containing Polyurethane Forumulation for Anti-Smudge Coatings and Superhydrophobic Textiles
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Durable and transparent anti-smudge coatings that repel both water- and oil-borne contaminants have many potential applications. Perfluorinated moieties were commonly used in the past to prepare water- and oil-repellant coatings, however these species are expensive and of significant environmental concern. Further, organic solvents have been traditionally used to formulate such coatings, however such solvent-based coating formulations emit volatile organic compounds and are a safety hazard. First reported in this thesis is the development of transparent and durable water-borne anti-smudge polyurethane coatings. These coatings are obtained by casting micellar solutions of a blocked polyisocyanate dispersed in water using a graft copolymer, polyol-g-PDMS, where the polyol backbone is water soluble and PDMS denotes poly(dimethyl siloxane). On these coatings, small 5-µL droplets of various liquids such as cooking and engine oils have no problem to glide cleanly off at substrate tilting angles < 5 °. Artificial fingerprint liquids, inks, and paints readily shrink into tiny droplets after application on them and their residues after solvent evaporation are readily wiped off with a tissue. Such waterborne coating formulations were also used to coat textile fibers, where they imparted superhydrophobic properties to the textiles. For both systems, the challenges associated with switching from a solvent-based to a water-based formulation for the targeted coatings will be discussed. The greenness of the coating formation process will also be highlighted for its practical value. In the future work, poorer water sliding behavior of NP-GLIDE coating (coatings bear nano-pools of grafted lubricating ingredient for dewetting enablement) will be improved with in-situ formation of free photo-cleavage PDMS chains. Also, the effect of chain length of PDMS to anti-smudge properties will be systematically investigated. Further, the robustness of these coatings will be tested.