Superhydrophilic, Underwater Directional Oil-Transport Fabrics with a Novel Oil Trapping Function.

In this study, we have prepared a novel superhydrophilic fabric that has underwater directional oil-transport capability. The fabric was prepared using a two-step process consisting of dip-coating of a cross-linkable polymer, which comprises both oleophilic and hydrophilic groups, onto the fabric substrate and single-side UV irradiation of the coated fabric. The fabric had in-air superhydrophilicity on both sides, and it can be wetted easily once immersed in water. The treated fabric showed underwater oleophobicity on the UV-exposed surface, whereas the unexposed back side still maintained underwater oleophilicity. At the optimized condition, the fabric in water transports oil automatically from the UV-exposed to the unexposed back side but stops oil transport in the opposite direction. Such a directional oil transport takes place without the need for oil prewetting or formation of a plastron layer on fabric. The UV irradiation time showed an effect on oil-transport ability. We further showed that the underwater directional oil-transport fabric had a novel "oil trapping" ability. When used to seal a container, the fabric can trap oil into the container, and once trapped, the oil was kept without releasing. This underwater directional oil-transport fabric may be useful for the development of high-efficiency oil recovery systems.