Facile preparation of cotton fabric with superhydrophilicity–oleophobicity in air and superoleophobicity under water by using branched polyethyleneimine/perfluorooctanoic acid composites

Abstract

It is extremely challenging to endow cotton fabric with superoleophobicity and superhydrophilicity at the same time as traditional oleophobic surfaces are generally hydrophobic as well. In this study, we report a facile method to fabricate cotton fabric exhibiting superhydrophilicity–oleophobicity in air and superoleophobicity under water by using branched polyethyleneimine/perfluorooctanoic acid composites. The surface morphology, elementary composition, and wettability were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and contact angle measurement, respectively. The results suggested that the modified cotton fabric retained its superhydrophilicity similar to the original cotton fabric; the water droplet can penetrate and diffuse within 1.86 seconds, but the oil resistance in the air is greatly improved, and the contact angles of rapeseed oil, hexadecane, and 1,4-dibromobutane are 128°, 123°, and 117°, respectively. In addition, the underwater superoleophobicity is also realized, as evidenced by its underwater contact angles of rapeseed oil, hexadecane, and 1,4-dibromobutane reaching 158°, 153°, and 152°, respectively. As a result, this developed cotton fabric can exhibit oil resistance during everyday use and achieve self-cleaning of oil stains under water. In addition, it can also be used for gravity-controlled oil–water separation and the oil/water separation efficiency can reach 96.5%. This research provides new ideas and inspiration for the preparation of superhydrophilic–superoleophobic materials.