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.
Layered heterostructure polyacrylic acid (PAA)/polyvinylidene fluoride–graphene nanosheet composites with a convex hexagonal columnar structure on the surface are prepared. The outer hydrophilic PAA hydrogel coating prevents underwater oil adhesion to the material. The inner hydrophobic layer microstructure endows the material with excellent mechanical properties even after immersion in seawater and at different pH values for 1 month.