A novel epoxy-based self-healing robust superhydrophobic coatings for oil/ water separation

Low durability greatly limits the practical application of superhydrophobic coating. In this study, we report a method of employing low surface energy materials and chemically reactive epoxy groups that possess strong adhesion on substrates in one system to solve the durability issue. A branched epoxy with dangling long polydimethylsiloxane (PDMS) tail was first synthesized through a thiol-Michael addition reaction. After curing, this coating exhibited superhydrophobicity with the contact angles (CAs) of 162.8 +/- 1.0 degrees and excellent durability towards strong acid (pH = 1.0), organic solvents as well as thermal treatment (150 degrees C, 24 h). Notably, the CAs of this coating could maintain above 150 degrees after 80 times of sandpaper abrasions, 100 times of tape-peeling, and 240 min of ultrasonic treatment, respectively. More importantly, the coating could spontaneously revert to a superhydrophobic state at room temperature after being plasma-treated to a superhydrophilic state. The coating fabric was utilized to separate the mixture of oil/water and the efficiencies for blend oil, corn oil, and soybean oil were found to be 97.7 +/- 0.4 %, 98.2 +/- 0.5 %, and 98.7 +/- 0.3 %, respectively. This work provides a novel strategy to create a fluorine-free, self-healing, and robust superhydrophobic coating.