Fabrication of filtration membranes

A filtration membrane comprising:

• a porous support layer;
• and
• a polymeric layer coated onto the porous support layer, wherein the polymeric layer is formed by coating a copolymer solution formed by dissolving a statistical copolymer in a mixture of a co-solvent and an organic solvent on the porous support layer, wherein the polymer layer is coagulated on top of the porous support layer to form a thin film composite membrane and, wherein the co-solvent is ethyl ammonium nitrate and the organic solvent differs from the co-solvent,
• wherein the copolymer solution comprises the statistical copolymer at 1 to 99 w/v %, the co-solvent at 5 to 49 v/v %, and the organic solvent at 51 to 95 v/v %;
• the statistical copolymer comprises zwitterionic repeat units and hydrophobic repeat units,
• wherein the zwitterionic repeat units constitute 30-50% by weight of the statistical copolymer, the hydrophobic repeat units constitute 50-70% by weight of the statistical copolymer;
• and the statistical copolymer is selected from the group consisting of poly((trifluoroethyl methacrylate)-r-(sulfobetaine methacrylate)), poly((methyl methacrylate)-r (sulfobetaine methacrylate)), poly((trifluoroethyl methacrylate)-r-(3-(2-vinylpyridinium-1-yl) propane-1-sulfonate)), poly((trifluoroethyl methacrylate)-r-(phosphorylcholine methacrylate), or poly((trifluoroethyl methacrylate)-r-(3-(2-vinylpyridinium-1-yl) butane-1-sulfonate));
• and the co-solvent is miscible with both water and the organic solvent, and
• wherein the membrane has an effective pore size of 0.5 to 5 nm and a water permeance of 10 Lm−2h−1bar−1 or higher.