Multifunctional surface treatment of boron nitride nanotube-coated polyimide films with atmospheric-pressure cold plasma

Polyimide (PI) surfaces coated with and without boron nitride nanotubes (BNNTs) were treated using an atmospheric-pressure cold plasma in open air. This treatment increased the surface wettability of the PI, measured by a decrease in water contact angle from 68° to 16°, resulting in a more uniform BNNT coating and improved surface adhesion. The plasma treatment of the BNNT-coated PI surfaces also effectively removed residual polymer surfactants used for BNNT dispersion in water, without causing any thermal damage due to the low plasma and PI's surface temperatures of 350 and 300 K, respectively. The reactive oxygen species in the plasma, such as hydroxyl molecules and oxygen atoms, played an important role in these processes. Atmospheric-pressure plasma can be employed in various applications in which thermally weak polymer-based substrates are coated with BNNTs.