Composite membrane and methods of fabrication thereof

A method of fabricating a composite membrane comprising a perfluorinated polymer layer physisorbed on a surface of a polymer substrate layer, the method, comprising:

• a) contacting a perfluorinated polymer solution with a surface of the polymer substrate layer in a drying chamber;
• and
• b) drying the perfluorinated polymer solution in the drying chamber to form the perfluorinated polymer layer physisorbed on the surface of the polymer substrate layer;
• wherein the perfluorinated polymer solution comprises a perfluorinated polymer and a C5-C18 perfluorinated solvent;
• wherein the perfluorinated polymer solution is dried under an air flow of about 0.05 m/s to about 1.5 m/s, at a relative humidity of less than 20% and at ambient temperature in order to form the perfluorinated polymer layer, the layer having a surface morphology of 0% to 10% of its surface comprising micro-structures;
• wherein the perfluorinated polymer layer has a thickness of about 5 nm to about 500 nm;
• wherein the perfluorinated polymer layer comprises a perfluorinated polymer or a copolymer or blend thereof;
• and
• wherein the polymer substrate layer comprises a non-perfluorinated polymer, or copolymer, or blend thereof.