In this work, the effects of surface chemistry and physics on the wetting behavior of polyurethane coatings were studied. The polyurethane coatings were applied on the glass slides in order to ensure the traarency of coatings during the investigation. Different molar percents of a surface energy reducing agent (SERA) were used to study the role of chemical modification in wetting of the polyurethane coatings. Different roughness patterns with different densities, sizes and shapes of surface features were formed. the optimum amount of modifier which altered both the chemistry and physics of the coating was found to be 5 mole%. The modifier increased the contact angle from 65 to 104°. In addition, a mechanism for the effects of additive on the wetting behavior and surface pattern of the coatings was presented for the first time. Nanocomposite coatings containing silica nanoparticles with and without the surface energy reducing agent were then prepared using a mixing technique. The lowest contact angle of 90° and highest contact angle of 109° were obtained for the coating with 8 wt% nanoparticles and 1 mole% perflourododecanol and the coating with 2 wt% nanoparticles and 5 mole% silicone-modified polyacrylate, respectively. In another approach, partially-cured polyurethane coatings were deep-coated several times in a dispersion containing surface-modified nanoparticles. It was found that the wetting behavior of these coating had a good compliance with the mushroom regime. Keywords: PU coatings, Surface energy reducing agent; Wetting; Lateral surface pressure, Nano roughness, mushroom-like regime
