Transparent omniphobic polyurethane coatings containing partially acetylated β-cyclodextrin as the polyol

Polyurethane is currently prepared from a polyisocyanate and a polyol derived from depletable and non-sustainable petroleum precursors. This paper reports the partial acetylation of beta-cyclodextrin (CD), derived from the renewable starch by enzymatic conversion, and the subsequent use of the acetylated CD as the polyol to produce a greener polyurethane. More importantly, a method for incorporating the low-surface-tension liquid poly(dimethyl siloxane), PDMS, into the new polyurethane formulation is reported. The final polyurethane coating bearing a liquid-like PDMS monolayer on its surface and nanometer-sized PDMS pools in its matrix is transparent and exhibits superior oil and water repellency. On the coating, various test liquids with surface tensions above similar to 22 mN/m cleanly glide at low substrate tilt angles and complex fluids such as ink and paint samples readily contract. While the green polyurethane coating and its omniphobic or anti-smudge counterpart are promising candidates for practical applications, the approaches used in this study should be adaptable for modifying other biomass-based precursors such as sugars or even possibly starch for preparing green polyurethanes and omniphobic polyureathanes.