Superhydrophobic and superoleophilic surfaces prepared by one-step plasma polymerization for oil-water separation and self-cleaning function

Abstract

Efficient superhydrophobic and superoleophilic thin films for oil-water separation and self-cleaning were prepared using the atmospheric-pressure plasma polymerization of hexamethyldisiloxane (HMDSO). A dielectric barrier discharge (DBD) plasma jet with argon (Ar) was used for the deposition of the functional thin films onto several substrates. The oil-water separation membrane was synthesized by the plasma polymerization of HMDSO on fabric and offset printing paper. The superhydrophobic coatings were deposited on glass to demonstrate their self-cleaning ability. The hydrophobicity of the thin films was found to vary significantly, depending on the operating parameters such as the deposition time, applied voltage, and gas flow rate. The gaseous shield of the plasma jet also affected the hydrophobicity to a large extent. Nitrogen (N2) rather than inert gases such as Ar and He exhibited an excellent shielding effect against the interference of ambient air on the plasma jet. The wettability of the glass was completely switched from superhydrophilic to superhydrophobic with the water contact angle (WCA) reaching 165° and the sliding angle about 2°. In addition, superoleophilicity was obtained with the oil contact angle (OCA) reaching 0° under the optimal operating conditions.