New tricks from old polymers

IOWA STATE (US) — Organic solar cells, light-emitting diodes, and thin-film transistors could be enhanced by polymers that mimic the properties of traditional inorganic semiconductors.

Researchers studying the relationship between polymer structures and the electronic, physical, and optical properties of the materials are also looking for ways to combine the polymers without the use of harsh acids and temperatures by making them soluble in organic solvents.

The building blocks of the work are a variety of molecules that are well suited for electrical applications because they efficiently transport electrons called benzobisazoles that are stable at high temperatures and can absorb photons.

If the polymers are lacking in any of those properties, chemical restructuring is possible.

“With these polymers, if you don’t have the properties you need, you can go back and change the wheel,” says Malika Jeffries-EL, assistant professor of chemistry at Iowa State University. “You can change the chemical synthesis and produce what’s missing.”

That isn’t possible with silicon and other inorganic materials for semiconductors, she says. “Silicon is silicon. Elements are constant.”

Jeffries-EL and colleagues have reported progress in Physical Chemistry Chemical Physics, Macromolecules, the Journal of Polymer Science Part A: Polymer Chemistry, and the Journal of Organic Chemistry.

“This research is really about fundamental science,” Jeffries-EL says. “We’re studying the relationships between structure and material properties. Once we have a polymer with a certain set of properties, what can we do?” The answers may be found in the molecules.

“In order to realize the full potential of these materials, they must be engineered at the molecular level, allowing for optimization of materials properties, leading to enhanced performance in a variety of applications,” Jeffries-EL writes in a research summary. “As an organic chemist, my approach to materials begins with small molecules.”

The work is supported in part by the National Science Foundation and the Iowa Power Fund.

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