Control of the chemical composition and thickness of deposited coatings over carbon nanotubes using acrylic acid plasma

In this study, it is demonstrated that the surface of carbon nanotubes can be coated with a polymer nanometer size film (nanocoating) with tailored surface polar behavior when treated with acrylic acid plasma. The polar behavior of the polymer nanocoating can be hydrophilic or hydrophobic depending deposition and erosion processes caused by ionized species in the plasma. In turn, deposition and erosion can be controlled by plasma power. Deposition dominates at 20 W power, where a significant amount of polymer nanocoating is produced with carboxylic acid functional groups in the surface thus having an hydrophilic behavior. On the contrary, a smaller amount of polymer nanocoating with hydrophobic behavior (i.e. without any functional groups on its surface) suggests that erosion is the dominant process when 40 W power is used. Finally, a competition between deposition and erosion processes results in different polar behavior and amount of polymer nanocoating depending of the treatment time.