A team from the Massachusetts Institute of Technology (MIT) has developed a lightweight polymer film that could be used as a protective coating on solar panels, as it is nearly impenetrable to gas molecules.
Under laboratory testing conditions, the nanometer-thick polymer was found to completely repel nitrogen, as well as other gases, under laboratory testing conditions. This differs from traditional polymers, which allow gases through as their molecules are loosely joined together, leaving tiny gaps that gases can pass through.
The laboratory’s novel material, known as 2DPA-1, is a two-dimensional polymer that self-assembles into molecular sheets using hydrogen bonds. It features a building block called melamine, which contains a ring of carbon and nitrogen atoms, which can expand in two dimensions and form nanometer-sized disks.
2DPA-1 differs from previous polymers as the disks stack on top of each other, held together by hydrogen bonds between the layers, making the structure strong and stable. MIT claims the polymer is stronger than steel but has only one-sixth of the density.
MIT’s research exposed 2DPA-1 to helium, argon, oxygen, methane, and sulfur hexafluoride and found its permeability to those gases was at least 1/10,000 that of any other existing polymer, making it almost as impermeable as graphene.
Scientists have been working to develop a graphene coating as a method of protecting solar cells from corrosion, but the scaling-up of a graphene film has proved difficult, as the film cannot be painted onto surfaces. As MIT’s 2DPA-1 polymer sticks easily because of its strong hydrogen bonds between the layered disks, it could prove a valuable alternative.
In the research paper “A molecularly impermeable polymer from two-dimensional polyaramids,” available in nature, the research team demonstrates that a 60-nanometer-thick film could extend the lifetime of a perovskite crystal by weeks, before adding a thicker coating could offer longer protection.
“Using an impermeable coating such as this one, you could protect infrastructure such as bridges, buildings, rail lines – basically anything outside exposed to the elements,” commented Michael Strano, MIT's Carbon P. Dubbs Professor of Chemical Engineering.
George Schatz, a professor of chemistry and chemical and biological engineering at Northwestern University, who was not involved in the research, called the results “remarkable”.
“Normally, polymers are reasonably permeable to gases, but the polyaramids reported in this paper are orders of magnitude less permeable to most gases under conditions with industrial relevance,” Schatz explained.
