Underwater Mechanically Robust Oil-Repellent Materials: Combining Conflicting Properties Using a Heterostructure.

The development of underwater mechanically robust oil-repellent materials is important due to the high demand for these materials with the increase in underwater activities. Based on the previous study, a new strategy is demonstrated to prepare underwater mechanically robust oil-repellent materials by combining conflicting properties using a heterostructure, which has a layered hydrophobic interior structure with a columnar hierarchical micro/nanostructure on the surface and a hydrophilic outer structure. The surface hydrophilic layer imparts underwater superoleophobicity and low oil adhesion to the material, which has oil contact angle of larger than 150° and adhesion of lower than 2.8 µN. The stability of the mechanical properties stemming from the interior hydrophobic-layered structure enables the material to withstand high weight loads underwater. The tensile stress and the hardness of such a heterostructure film after 1 month immersion in seawater and pH solution are in the range from 83.92 ± 8.22 to 86.73 ± 7.8 MPa and from 83.88 ± 6.8 to 86.82 ± 5.64 MPa, respectively, which are superior to any underwater oil-repellent material currently reported.