Researchers Find New Properties in an Old Material

Louis Madsen (Virginia Tech)

Researchers at Virginia Tech in Blacksburg have devised a way to measure and manipulate the internal structure of Nafion, a common polymer, to expand the material’s applications. The research chemists’ results are published in the 19 June issue of the journal Nature Materials (paid subscription required).

Nafion was developed in the 1960s by DuPont, and is made up of molecules that combine the toughness and non-stick properties of Teflon with the conductive properties of an acid, such as battery acid. The material’s structure has a network of tiny channels, nanometers in size, that carries water or ions quickly through it.

That network of channels, however, does not follow regular patterns, which made it difficult to understand with standard analysis tools, such as transmission electron microscopes, says chemistry professor Louis Madsen (pictured right). His team of fellow faculty, postdoc, and student researchers had to use more powerful tools to uncover Nafion’s properties.

The team used nuclear magnetic resonance (NMR) to measure molecular motion, and used a combination of NMR and X-ray scattering to measure molecular alignment within Nafion. They found water molecules could serve as indicators of the material’s structure on conductivity, which led them to locally aligned aggregates of polymer molecules.

“The molecules align like strands of dry spaghetti lined up in a box,” says Madsen. “We can measure the speed or diffusion of the water molecules and the direction they travel within those structures, which relates strongly to the alignment of the polymer molecule strands.”

The molecular pattern became clearer when the researchers stretched Nafion, and measured its structure and water motion. They found a structure in stretched Nafion similar to that of liquid crystals, used in LCD televisions, projectors, and screens. In liquid crystals and stretched Nafion, molecules line up with each other, and move faster along the direction of the stretch, and in a predictable way.

These newly discovered properties of Nafion have potential applications in fuel cells, organic batteries, and reverse-osmosis water purification. The research is supported by Madsen’s National Science Foundation Faculty Early Career Development (CAREER) Award. The research is also supported by the U.S. Army Research Office.

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