Semiconducting and Metallic Polymers: The Fourth Generation of Polymeric Materials
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Semiconducting and
Metallic Polymers: The Fourth Generation of Polymeric Materials Alan J. Heeger
The following is an edited transcript of the plenary lecture presented by Alan J. Heeger at the 2001 MRS Spring Meeting on April 18, 2001, in San Francisco. Heeger and colleagues Alan G. MacDiarmid and Hideki Shirakawa shared the Nobel Prize in Chemistry for 2000 for the “discovery and development of conductive polymers.”
A Brief History Prior to receiving the Nobel Prize in chemistry in 2000 for my work in polymers, polymer science had been recognized three times. The first Nobel Prize in chemistry for polymer science was awarded in 1953 to Hermann Staudinger, for his pioneering work in the 1920s. At that time, the concept of macromolecules was new, and his ideas were controversial. However, the data prevailed, and he was awarded the Prize “for his discoveries in the field of macromolecular chemistry.” The next major event in polymer science was the discovery and invention of nylon by Wallace Carothers at the Dupont Company in 1935. Although Carothers died as a young man, his discoveries created an industry. I have little doubt that his work was deserving of a Nobel Prize and probably would have been awarded. The next related Prize went to Karl Ziegler and Giulio Natta in 1963 for their work on polymer synthesis in the 1950s. The Ziegler–Natta catalysts made possible the large-scale production of polymers such as polypropylene. They were awarded the Nobel Prize in chemistry “for their discoveries in the field of chemistry and technology of high poly-
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mers.” In 1974, the Prize for chemistry went to Paul J. Flory, who was a giant in this field. He was awarded the Nobel “for his fundamental achievements, both theoretical and experimental, in the physical chemistry of macromolecules.” All of the materials in the three generations of polymers that were studied by Staudinger, Carothers, Ziegler, Natta, and Flory are insulators. The first generation of polymeric materials consists of natural polymers such as leather, bone, and fibers such as silk. The second generation of polymeric materials is synthetic polymers, initiated by the work of Carothers and greatly enhanced by Ziegler and Natta. The third generation, which I associate with the work of Flory, consists of the “engineering plastics” that are so important in our lives today. The fourth generation of polymers, as designated by Swedish professor Bengt Ranby in the Nobel symposium in 1991, is known as “conducting polymers.” The 2000 Prize in chemistry is the first Nobel Prize for materials science as we know it today, that is, an interdisciplinary field with contributions from chemistry, physics, and materials processing. When I am asked to explain the importance of the “discovery and development of conducting polymers,” I offer two basic answers. First, prior to 1977, the words “conducting” and “polymers” did not go together; conducting polymers did not exist and perhaps could not exist. Second, conducting polymers offer a unique combination of properties that
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