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

Abstract

ethyl methacrylate-co-ethylene glycol dimethacry late] (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, showing a 15% to 43% reduction in permeation. Cell adhesion tests were carried out using Escherichia coli, and the coated RO membranes showed superior antifouling performance compared with the bare RO membrane. This is the first time that the library of iCVD functional groups has been extended to charged zwitterionic moieties, and the zwitterionic coatings have been applied on delicate substrates, such as RO membranes.

A comprehensive review on surface modified polymer membranes for biofouling mitigation

“…Initiated chemical vapour deposition (iCVD) is an all-dry free radical polymerization technique performed at low temperatures and low operating pressures [96]. A key feature of iCDV is the introduction a free radical initiator species, which is thermally cracked over a heated filament to induce vapour phase monomers to deposit coatings at high rates [97].…”

“…Using this technique, an antifouling copolymer layer containing poly-(sulfobetaine) zwitterionic groups was covalently grafted on commercial RO membrane [96]. After iCVD deposition a smooth and conformal coating is formed on top of the polyamide membrane layer (Fig.…”

Chemical Vapor Deposition for Solvent‐Free Polymerization at Surfaces

“…Reproduced with permission. [ 28 ] Copyright 2011, American Chemical Society. decomposition mechanism, a tungsten catalyzer was installed in the same chamber to remove the carbonized surface of the NiCr catalyzer.…”

“…This system is buckled to construct highly ordered herringbone patterns through a new sequential wrinkling strategy (Figure 1 b). [ 27 ] In a similar approach, Yang et al [ 28 ] modifi ed the amine groups present in RO membranes with maleic anhydride (MA) to facilitate covalent grafting of a zwitterionic polymer coating. Without MA grafting, the zwitterionic fi lms delaminated from the membrane when placed in water.…”

“…A zwitterionic coating deposited on reverse osmosis membranes using iCVD exhibited superior antifouling performance compared with to bare membranes (Figure 3 d). [ 28 ] …”