Sunday, 24 July 2011

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Biography of Alan G. MacDiarmid

Alan MacDiarmid, co-discoverer of the field of conducting polymers, more commonly known as “synthetic metals,” was the chemist responsible in 1977 for the chemical and electrochemical doping of polyacetylene, (CH)x, the “prototype” conducting polymer, and the “rediscovery” of polyaniline, now the foremost industrial conducting polymer. Alan G. MacDiarmid shared a Nobel Prize in Chemistry with Dr. Alan J. Heeger and Dr. Hideki Shirakawa.

The Royal Swedish Academy of Sciences awarded the prize to the three for the discovery and development of conductive polymers. Alan G. MacDiarmid (born April 14, 1927; mother, Ruby and father, Archibald MacDiarmid ) grew up in New Zealand, and received his Ph.D. at University of Wisconsin 1953 and at University of Cambridge, UK, 1955. He was associate professor at University of Pennsylvania 1956 and received a professorship there 1964. Since 1988 he is Blanchard Professor of Chemistry.

In 1973, he began research on (SN)x, an unusual polymeric material with metallic conductivity. His interest in organic conducting polymers began in 1975 when he was introduced to a new form of polyacetylene by Dr. Hideki Shirakawa at the Tokyo Institute of Technology. The ensuing collaboration between MacDiarmid, Shirakawa and Alan Heeger (then at the Department of Physics at the University of Pennsylvania) led to the historic discovery of metallic conductivity in an organic polymer.

MacDiarmid recalled that he invited Shirakawa to Penn to study polymers after they met over a cup of green tea at a conference at the Tokyo Institute of Technology, where MacDiarmid was giving a lecture. When MacDiarmid-who noted that he likes “pretty things”-showed Shirakawa a “golden-colored” polymer made of silver nitride, Shirakawa showed him a “beautiful silvery polymer” made of polyacetylene. “I said, ‘If I can get some money, could you come and join me for a year at Penn?’” MacDiarmid said.

“And he said ‘Yes.’” While at Penn, they soon found that Shirakawa’s silvery polymer “showed some conductivity, not very high, but this elemental analysis also showed that there was impurity in it. So we said, ‘Well, obviously, you make it more pure, you get a higher conductivity.’” But, MacDiarmid noted, Shirakawa found that “the purer he got it, the more the conductivity decreased instead of increasing.” They then added iodine, which removed some of the tightly packed electrons, “and suddenly the conductivity increased within a few seconds to millions and billions of times higher than what it was before.”

MacDiarmid and Heeger enjoyed a “very, very crucial and successful collaboration for about 10 years,” MacDiarmid recalled. “We would arrange to get together every Saturday morning-we strictly said not to discuss anything specific; purely to sit down and let our minds wander and consider crazy things, which we did.” From his point of view, MacDiarmid said, the “whole climate of Penn is really just great” for research, and its interdisciplinary strengths are complemented by the quality of its students. “We all know that the research done in a given research group cannot be better than the students-undergraduate, graduate or post-doctoral,” he said. “If you have very good people working-not for you but with you, then the chances of finding very important, critical, unexpected things are pretty high.”

This initial discovery and ensuing studies, in collaboration with Shirakawa, resulted in the first chemical doping of (CH)x and detailed physics studies with Heeger. That an organic polymer could be readily doped to the metallic regime introduced a phenomenon, completely new and unexpected to both the chemistry and physics communities.

This unleashed a flood-gate of research world-wide in chemistry and physics concerning interrelationships between the chemistry, structure and electronic properties of semiconducting and metallic organic polymers which has continued to expand unabatedly to this day.

Technological opportunities for application of these materials in such diverse areas as rechargeable batteries, electromagnetic interference shielding, antistatic dissipation, stealth applications, corrosion inhibition, flexible “plastic” transistors and electrodes, electroluminescent polymer displays, to name but a few, continue to be actively pursued.

MacDiarmid’s current scientific interests are centered around the most technologically important conducting polymer, polyaniline, and its oligomers with special interest in those isomeric forms which might contribute to the greatest degree in promoting high conductivity and enhanced mechanical properties in polyaniline. He is also actively involved in the study of aniline oligomers in reversible sensors for volatile organic compounds down to a few ppm. His studies on light-emitting organic polymers involve investigation of the new phenomenon in which traces of ionic species in the emissive layer greatly enhance selected desirable characteristics.

During the past 20 years he has been involved exclusively with conducting polymers, particularly the synthesis, chemistry, doping, electrochemistry, conductivity, magnetic and optical properties and processing of polyacetylene and polyaniline. He is the author/co-author of approximately 600 research papers and 20 patents. He is the recipient of numerous awards and honorary degrees both nationally internationally. Most recently, he was named recipient of the 1999 American Chemical Society Award in Materials Chemistry.

Alan G. MacDiarmid shared a Nobel Prize in Chemistry with former Penn physics professor Dr. Alan J. Heeger (now at the University of California-Santa Barbara) and Dr. Hideki Shirakawa of the University of Tsukuba, Japan. The Royal Swedish Academy of Sciences awarded the prize to the three for the discovery and development of conductive polymers.

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