Preparation And Application Of Underoil Superhydrophilic Materials

Superwetting materials become a research focus due to their special wetting performances and wide applications. Compared with the traditional research about superhydrophobic/superhydrophilic surfaces in air, research about wetting performance in complex environment, such as in oil, is still limited, especially those about underoil superhydrophilic materials is extremely rare. In fact, such research is very important because it can not only provide some new superwetting materials with novel functions, but also can be used in many practical applications, for example, oil/water separation. Herein, we advanced research about underoil superhydrophilic materials, surface wetting control, and application in oil/water separation.The foamy copper was used as the substrate, it is found that after immersion into the solution containing NaOH and(NH4)2S2O8, the surface of foamy copper would be covered by lots of Cu(OH)2 nanowires. The wettability of the foamy copper is changed from the original underoil hydrophobicity to the underoil superhydrophilicity. After growth of Cu(OH)2 nanowires, a lot of hydroxyl groups would be introduced onto the surface, which can enhance the surface hydrophilicity, together with the amplified effect of the nanostructures, the material would show the underoil superhydrophilicity. Furthermore, based on the special underoil superhydrophilicity, the material was applied successfully in the capture of water in oil.As to the oil/water separating materials, fouling problem is difficult to be avoided. In this work, nanostructured foamy copper with underoil superhydrophilicity was prepared, and special antifouling ability can be observed on the material. When the material is fouled with oil, after a simple wash process by water, it can return to the original clean state, demonstrating a good antifouling property. The special antifouling ability can be ascribed to the underoil superhydrophilicity of the material. Due to the special antifouling ability, we advanced a novel in-situ separation method for oil/water mixture.Until now, smart surfaces that can transit between the superhydrophobicity and superhydrophilicity can only be realized in air, in other environment, for example, in oil, it is still a challenge. Herein, nanowires were firstly produced on the silicon substrate, by using a simple layer-by-layer technique, PDDA and PSS molecules were assembled onto the nanostructured surface alternately. It is found that the underoil superhydrophobicity and underoil superhydrohilicity can be achieved, respectively when the PSS and PDDA is exposed to water, respectively. The smart ability of the surface is ascribed to different molecular configurations of PDDA and PSS and the enhanced effect of nanostructures.