Self-healing superhydrophilic polyurea composite coating for durable oil/water separation

Oil/water separation membranes are prone to damage from environment, which limits their application in treating oily wastewater. Improving the durability of these membranes remains challenging. In this study, we incorporated robust polyurea (PU) into a coating. The structure of polyurea was modulated to introduce multiple hydrogen bonds and dynamic disulfide bonds, thus affording a polyurea coating with 90.53 % self-healing efficiency at 80 °C. The disulfide bonds imparted self-healing properties to the coating, while the multiple hydrogen bonds enhanced its stability. Phytic acid (PA), a natural product, and polyethyleneimine (PEI), a positronic compound, were synergistically combined with the polyurea coating to increased hydrophilicity through hydrogen bonding, coordination chelation, and electrostatic interactions. PEI/PA/SHPU@SSM was obtained by applying the composite coating to a stainless steel mesh surface. After 32 oil/water separation cycles, the self-healing group maintained a separation efficiency of 97.6 %, outperforming the non-self-healing group by 1.3 %. After 30 abrasion cycles, the underwater oil contact angle of the self-healing group was 147.1°, which was 6.5° higher than that of the non-self-healing group. The results highlight the effectiveness of the self-healing in enhancing the oil/water separation durability of PEI/PA/SHPU@SSM. This study offers new insights for improving the durability of superhydrophilic coating materials.