Two-faced fabric separates oil from emulsions

A new polymer-coated fabric could make it easier to separate troublesome emulsions, such as those that can occur during industrial-scale syntheses of organic chemicals or when oil is accidentally released into waterways. The material, developed by Guojun Liu, Zijie Wang, and Shuaishuai Huang of Queen’s University, in Ontario, is known as a Janus fabric because, like its namesake Roman god with two faces, it has two sides, each with a different property—one hydrophilic and one hydrophobic. The new Janus fabric is made by coating cotton with a block copolymer containing hydrophobic poly(dimethylsiloxane), known as PDMS, along with hydrophilic poly(N,N-dimethylaminoethyl methacrylate), known as PDMAEMA (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201607581). In air, PDMS orients to the surface of the fabric. But when the fabric is exposed to an emulsion, the material acquires its Janus nature, with the PDMAEMA portion of the polymer migrating toward the emulsion and the PDMS moving to the opposite side of the fabric. Oil droplets from the emulsion start aggregating in the presence of the PDMAEMA and then move to the hydrophobic PDMS side. As such, the fabric serves two functions: It de-emulsifies and separates the oil.