Bioinspired nonswellable ultrastrong nanocomposite hydrogels with long-term underwater superoleophobic behavior

Hydrogels, intrinsic hydrophilic materials, have been extensively used for fabrication of underwater superoleophobic substrates. However, the swelling behavior, poor salt tolerance and weak mechanical properties of hydrogels in high-salinity marine environment have significantly negative impacts on underwater oil-repellent effect. Herein, an ultrastrong hydrogel maintaining long-term volume stability in seawater is developed by introducing strong coordination interactions between nanoparticles and polymer matrix. The tensile strength, elastic modulus, and compressive strength of this nonswellable hydrogel are up to 9.2 MPa, 52.3 MPa and 48.5 MPa respectively, superior to those of all other reported underwater superoleophobic hydrogels. After introducing lotus-leaf-like micro/nanostructures on this nonswellable hydrogel, the structured surface demonstrates durable superoleophobicity and ultralow oil adhesion (less than 1 μN) under seawater. Notably, the 3D optical images and SEM images reveal that lotus-leaf-like micro/nanostructures on the nonswellable hydrogel surface can be well preserved even after immersion in seawater for one year, enabling the nonswellable structured hydrogel still to show anti-crude-oil-adhesion property under seawater.