Facile Fabrication of Janus Membranes with Antifouling Properties for Membrane Distillation

An antifouling Janus membrane for membrane distillation (MD) was fabricated via a facile photoinitiated chemical vapor deposition process. The hydrophilic polymer poly(2-hydroxyethyl methacrylate) (pHEMA) was selectively deposited on one side of the polytetrafluoroethylene membrane, while the other retained its hydrophobicity. The fabricated Janus membrane exhibited an overall maintained porous structure, owing to the advantages of vapor-phase polymer deposition; however, the asymmetric deposition of hydrophilic pHEMA on a single side of the membrane induced different properties on each side. The Janus properties were identified by using chemical analyses and contact angle measurements. The Janus membranes showed no significant differences in MD performance with a saline water feed compared with the pristine membrane. Moreover, in the MD test of the oil emulsion in saline water, the Janus membrane exhibited superior oil antifouling properties, whereas the pristine membrane was immediately fouled. Furthermore, the stability of the pHEMA-coated Janus membrane after MD testing was confirmed.