A method of preparing a filtration membrane, the method comprising: providing a copolymer solution by dissolving poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)) in a mixture of ethyl ammonium nitrate and trifluoroethanol, wherein the ethyl ammonium nitrate is present in 20 v/v% of the copolymer solution; coating the copolymer solution onto a porous support layer to form a polymeric layer thereon, coagulating the polymeric layer on top of the porous support layer to afford a thin film composite membrane, and immersing the thin film composite membrane into a water bath to obtain a filtration membrane, wherein the poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)) statistical copolymer comprises zwitterionic repeat units and hydrophobic repeat units, wherein: the zwitterionic repeat units constitute 30-50% by weight of the poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)), the hydrophobic repeat units constitute 50-70% by weight of the poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)); and wherein either: (i) coagulating the polymeric layer on top of the porous support layer is achieved via air drying for 20 seconds; or (ii) the polymeric layer on top of the porous support formed in the coating step is immersed into a non-solvent bath of isopropanol for 20 minutes prior to immersing in the water bath. providing a copolymer solution by dissolving poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)) in a mixture of ethyl ammonium nitrate and trifluoroethanol, wherein the ethyl ammonium nitrate is present in 20 v/v% of the copolymer solution; coating the copolymer solution onto a porous support layer to form a polymeric layer thereon, coagulating the polymeric layer on top of the porous support layer to afford a thin film composite membrane, and immersing the thin film composite membrane into a water bath to obtain a filtration membrane, wherein the poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)) statistical copolymer comprises zwitterionic repeat units and hydrophobic repeat units, wherein: the zwitterionic repeat units constitute 30-50% by weight of the poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)), the hydrophobic repeat units constitute 50-70% by weight of the poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)); and the zwitterionic repeat units constitute 30-50% by weight of the poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)), the hydrophobic repeat units constitute 50-70% by weight of the poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)); and wherein either: (i) coagulating the polymeric layer on top of the porous support layer is achieved via air drying for 20 seconds; or (ii) the polymeric layer on top of the porous support formed in the coating step is immersed into a non-solvent bath of isopropanol for 20 minutes prior to immersing in the water bath. (i) coagulating the polymeric layer on top of the porous support layer is achieved via air drying for 20 seconds; or (ii) the polymeric layer on top of the porous support formed in the coating step is immersed into a non-solvent bath of isopropanol for 20 minutes prior to immersing in the water bath.