Superhydrophobic UHMWPE Foams with High Mechanical Robustness and Durability Fabricated by Supercritical CO₂Foaming

The low durability and stability of superhydrophobic foams and high fabrication costs are the main reasons that limit their practical applications in water remediation and oil recycling. Herein, an extremely superhydrophobic and exceptionally robust foam was developed based on ultrahigh-molecular weight polyethylene (UHMWPE) by supercritical carbon dioxide (scCO2) foaming and subsequent surface modification. The developed foam comprises a highly porous structure decorated with hydrophobic silica nanoparticles and aligned UHMWPE crystallites, constructing a complex micro-nanosized hierarchical morphology, which contributed to an unprecedented water contact angle (WCA) of 162° and a sliding angle of 1°. When used in selective oil absorption and oil/water separation, the foam demonstrated about 100% separation efficiency in repetitive use and even under a vacuum of -70 Kpa due to its high water repellency. More importantly, the foam has outstanding tolerance against mechanical damages such as ultrasonication, bending and twisting, tape peeling, steel wool abrasion, and knife scratching. The surface could maintain the hierarchical structure and a WCA of over 156° after enduring different damages. Moreover, when the surface is clogged, the foam could restore its superhydrophobicity by arbitrary fracturing and cutting, resulting in a theoretically unlimited lifespan. This work not only proposes a UHMWPE-based superhydrophobic foam with extremely high superhydrophobicity, durability, and separation efficiency but also provides insights into the design and mass production of ultraefficient and robust superhydrophobic porous materials for practical applications.