Spray-assisted nanocoating of the biobased material urushiol.

We have demonstrated the spray-assisted coating of the catechol derivative, urushiol. Spraying a mixture of urushiol and iron(II) acetate formed a uniform coating about 10 nm thick, as confirmed by AFM observations. XPS measurements revealed that various substrates, including polyolefins and thermosetting resins, were successfully coated with urushiol. The coating showed good solvent tolerance and coating adhesion after baking at 100 °C for 10 min or after aerobic oxidation for several days. Interestingly, quartz crystal microbalance (QCM) measurements and strain-induced elastic buckling instability for mechanical measurements (SIEBIMM) revealed that density and Young's modulus of the spray-assisted nanocoatings were higher than those of spray-coated samples. Moreover, the coating was uninvolved in physical properties except surface properties, as demonstrated by several experiments. Because urushiol is a promising biobased material, our unique spray-assisted coating technique could provide a general approach for material-independent surface modification techniques that are environmentally sustainable.