In Situ Generated Janus Fabrics for the Rapid and Efficient Separation of Oil from Oil‐in‐Water Emulsions

A cotton fabric was coated with a polymer that contains both poly(dimethyl siloxane) (PDMS) and poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA). When the repeat unit number of PDMS is about three‐fold that of PDMAEMA and the fabric is exposed to air, the fabric is superhydrophobic because PDMS in the coating covers the PDMAEMA chains. Upon contact with an oil‐in‐water emulsion, the water‐soluble PDMAEMA rises to the top and the side in contact with the emulsion becomes hydrophilic. The emerged PDMAEMA chains then cause the emulsion droplets to coagulate, and the aggregated oil fills the pores on the superhydrophobic side of the fabric. The oil‐impregnated side remains hydrophobic even upon prolonged contact with water. Thus, a Janus fabric is elegantly generated in situ and sustained. This easy‐to‐prepare Janus fabric rapidly and efficiently separates oil from emulsions and may find practical applications.