Synthesis of new semi-fluorinated polysilazanes and their amphiphobic coating applications

Abstract

A series of new semi-fluorinated polysilazanes (FPSZs) were prepared via ammonolysis of dichloro(1H,1H,2H,2H-perfluorodecyl)methylsilane (DCFMS) and dichloromethylsilane. The FPSZs consist of methylsilazane and fluorinated silazane moieties, which provide excellent adhesion to substrates and a low surface energy, respectively. FPSZs with various DCFMS ratios (0.2–100 mol%) were obtained with a facile control over the fluorinated composition by adjusting the precursor ratio. The water and oil contact angles increased as a function of DCFMS loading and saturated at values of 112° and 54°, respectively, for just 0.4 mol% of DCFMS coated on flat Al substrates. To obtain superamphiphobicity, a hierarchical nano-micro rough surface for the Al plates is required for which they were etched with HCl and then immersed in boiling water. The FPSZ containing 26.7 mol% (FPSZ26.7) of fluorinated moiety exhibited a water contact angle of 173° and an oil contact angle of 148° when it was coated on the rough Al substrate. The water contact angle of the rough Al plate coated with a non-fluorinated organic polysilazane (OPSZ) was also higher than 160°, but the measurement of ice adhesion force failed after 40 icing/melting cycles (338 kPa before icing) owing to physical damage to the surface in the icing/melting process. However, the rough Al plate coated with FPSZ26.7 exhibited improved anti-icing properties—the ice adhesion strength was 131 kPa after the 40 icing/melting cycles (73 kPa before the icing tests).