Unexpected superhydrophobic polydopamine on cotton fabric

Abstract

Polydopamine (PDA) is the mussel-inspired coating with the outer-exposed functional groups such as amine as well as hydroxyl and widely used in the field of surface modification. Due to the polar functional groups, the PDA is generally hydrophilic. Herein, for the first time, we have unexpectedly fabricated a durable superhydrophobic PDA coating via a quite normal deposition on the cotton fabric but failed on other fabrics such as linen and silk. This suggests that such a cotton fabric might induce the exposing of the hydrophobic benzene moiety of PDA and endow the surface non-wettability, which is further enhanced by the rough surface structures of the fabric. In addition, the durability of the surface superhydrophobicity against mechanical impacting (abrasion), chemical impacting (immersion in acid, alkali, and boiling water), and a combining of chemical / mechanical impacting (laundering and ethanol ultrasonication) has also been assessed. The behaviors are comparable or even superior to the typical reported results in the references except for the immersion test in alkali due to the inherent instability of PDA in alkali solution. A sample application study case is also presented to demonstrate its capabilities in the recyclable oil / water separation.