A Solvent Regulated Hydrogen Bond Crosslinking Strategy to Prepare Robust Hydrogel Paint for Oil/Water Separation

Hydrogel modified porous matrix with the super-wetting surface (i.e., super-hydrophilic/underwater super-oleophobic) is ideal for oil/water separation. However, the deterioration in mechanical strength and separation efficiency during the swelling process and complicated synthesis procedure limits its industrial application. In this study, a strategy of using ethanol to dynamically regulate the hydrogen bond crosslinking between polyvinyl alcohol (PVA) and tannic acid (TA) is proposed to prepare a “hydrogel paint”, which can be simply applied on the porous substrate surface by different one-step operations (dipping, brushing, spraying, etc.) without additional cross-linking. The underline mechanism is attributed to the re-establishment of intermolecular hydrogen bond mediated cross-linking between PVA and TA during ethanol evaporation. Consequently, the resultant hydrogel coating exhibits ultra-high strength (>10 MPa), swelling volume stability, and excellent oil-water separation efficiency (>99%). This study will provide new insights into the scalable fabrication of hydrogel-coated porous materials for oil/water separation in industrial scenarios.