Facile in situ PEGylation of polyamide thin film composite membranes for improving fouling resistance

We report a novel approach for in situ PEGylation of thin film composite (TFC) reverse osmosis (RO) membrane for sustained performance. The approach was based on use of end-functionalized polyethylene glycol (MPD-PEG-MPD or MeO-PEG-MPD) with end groups structure resembling the structure of m-phenylenediamine (MPD), commonly used for preparation of TFC membrane. Michael addition reaction between MPD and acrylate-terminated-polyethylene glycol (AA-PEG-AA or MeO-PEG-AA) produces such type of end-functionality for further use in interfacial polymerization (IFP) with conventionally used trimesoyl chloride (TMC). PEGylated TFC membranes exhibited superior antifouling property during water desalination in presence of fouling agent (protein) compared to non-PEGylated TFC membrane. The best results were obtained with the membranes prepared by addition of 0.25-0.5% (w/v) of AA-PEG-AA or MeO-PEG-AA to the MPD solution (2% w/v in water) for Michael addition reaction prior to IFP with TMC (0.125% w/v in hexane) in as much as the antifouling property was enhanced and the performance (salt rejection efficiency and flux) remained almost unaffected. TFC membranes were characterized by Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), contact angle (θ), scanning electron microscope (SEM), atomic force microscope (AFM) and CHN analyses. The incorporated PEG remained stable in the polyamide network and is mainly attributed to the participation of both MPD and MPD-PEG-MPD or MeO-PEG-MPD in the IFP process.