Surface-Tethered Zwitterionic Ultrathin Antifouling Coatings on Reverse Osmosis Membranes by Initiated Chemical Vapor Deposition

Poly[2-(dimethylamino)ethyl methacrylate-co-ethylene glycol dimethacrylate] (PDE) thin films were synthesized via initiated chemical vapor deposition (iCVD) and reacted with 1,3-propane sultone to obtain the zwitterionic structure. The cross-linker ethylene glycol dimethacrylate (EGDMA) was utilized to make the copolymer insoluble in water. The composition of the copolymer was tuned by varying the flow rates of precursors and calculated from Fourier transform infrared spectroscopy (FTIR) spectra. The zwitterionic coatings were covalently grafted on to reverse osmosis (RO) membranes, and surface characterizations were carried out. Scanning electron microscope (SEM) and atomic force microscope (AFM) revealed that the iCVD zwitterionic coatings were conformal and smooth over the RO membrane, and the coating thickness can be measured by using ellipsometry. Salt rejection was not impaired by the coating. Permeation tests were carried out under different feed pressures, film thicknesses, and film compositions, ...