Seeing the vivid colors of azo dyes appear as he synthesized molecules during high school lab sessions inspired Klaus Muellen, 64, to study chemistry at university. His attraction to colorful chemistry never went away: Muellen, a director at the Max Planck Institute for Polymer Research, in Mainz, Germany, has won this year’s ACS Award in Polymer Chemistry in part for developing double-stranded polyphenylene polymers that serve as a basis for blue-light-emitting diodes.
Dyes aside, Muellen’s contributions to polymer chemistry range from the invention of new approaches for building optoelectronic polymers to the development of materials for lithium and hydrogen storage. His group has also figured out how to elegantly build various aromatic polymers, nanocomposites, and bioconjugates.
In sum, Muellen “is one of the most creative and prolific polymer chemists in the world,” says Krzysztof Matyjaszewski, a chemist at Carnegie Mellon University.
“One of the most difficult challenges in polymer synthesis has been preparation of soluble, fully aromatic polymers,” Matyjaszewski notes. Muellen got around this challenge by designing hyperbranched and dendritic polymers through Diels-Alder reactions and Suzuki couplings. The dendrimers are soluble, stable, and transparent and can be functionalized at the periphery, “forming very interesting core-shell structures soluble in various solvents, even in water,” Matyjaszewski says. “They can be used for light harvesting and light emission but also for detection of explosives at the parts-per-million level, drug delivery, and gene transfection.”
Muellen initially studied chemistry at the University of Cologne, in Germany, before moving to the University of Basel, in Switzerland, to pursue a Ph.D. under Fabian Gerson. He then moved on to Zurich to do a postdoc and habilitation at the Swiss Federal Institute of Technology. In 1979 he took his first professorship at the University of Cologne before being recruited to the University of Mainz in 1983. In 1989 he joined the Max Planck Institute for Polymer Research, where he remains today. Muellen also served as president of the German Chemical Society in 2008–09.
In addition to a love of soccer that is so strong he gave up playing only after his third hip surgery, Muellen also plays the trumpet for fun, a hobby he picked up because of his scientific colleagues. As his 40th birthday approached, Muellen joked that he “needed to start something new.” After his colleagues heard him rave about a trumpet’s role in a Bach performance he’d attended, “three weeks later I got a trumpet for my birthday. I felt obliged to learn it.”
In science, Muellen wasn’t always drawn to polymer chemistry. Early in his career he had viewed polymers as the “junk on top of a chromatographic column.” But that changed as he became inspired by the challenge to “create well-defined macromolecular systems” with reliable and encodable features. Muellen says he’s most satisfied with his work to apply polymer chemistry methods for building graphene nanoribbons—and his group’s development of the double-stranded polyphenylene polymers that emit the lovely blue light.
Muellen will present the award address before the ACS Divisions of Polymer Chemistry and of Polymeric Materials: Science & Engineering.