Hydrophobic coatings from plasma polymerized vinyltrimethylsilane

Thin-films have been deposited onto silicon and metal substrates by plasma polymerization of vinyltrimethylsilane (VTMS), to provide hydrophobic coatings for dropwise condensation of steam. The deposition conditions have been sampled by a set of statistically designed experiments, and the films' thicknesses, water droplet contact angles, elemental compositions (by XPS), and -CH_x contents have been measured. There is a strong correlation between these film properties and their deposition conditions. The films that continue to provide successful long-term dropwise condensation had been deposited at a low rate onto heated substrates, such that they have high water contact angle and high -CH_x content. This required a plasma that provided a low electron energy input per precursor species collision.