Large-area, transferable sub-10 nm polymer membranes at the air-water interface

Large-area, pinhole-free, and ultrathin polymer membranes with thicknesses of only a few nanometers have attracted increasing attention for their applications in molecular separation, flexible optoelectronics, and sensors. They can potentially be developed for surface protection as well. In this study, we report an effective way to obtain large-scale polymer coatings with a thickness down to 10 nm, which effectively protects metals from corrosion. We develop a facile and scalable method to fabricate freestanding polymer membranes with thickness below 10 nm by dropping the precursor polymer solution on a water surface. By optimizing the surface tension of the polymer solution, the solution could spontaneously spread on the water surface to form a continuous and uniform solid membrane, collected as a freestanding thin membrane. The obtained polymer membranes could then easily be transferred on a metal substrate as highly flexible and stable anti-corrosion coatings. Electrochemical measurements performed in a 0.1 M Na2SO4 solution demonstrated the excellent anti-corrosion properties of the sub-10 nm polymer membranes whose corrosion rate was less than 1% of the corrosion rate of the bare metal. We also demonstrate that the polymer membrane exhibits high performance as a protection layer for flexible circuits.