Chemist and materials scientist Hideki Shirakawa, who shared the Nobel prize in chemistry for his discovery and advancement of conductive polymers in 2000, has passed away at the age of 90. Shirakawa, a trailblazer whose contributions contested the common perception that polymers are insulators and led to the breakthrough of conductive polymers, died on 24 August.
Shirakawa garnered over 16,000 citations for his research in the field of conductive polymers, including the pivotal paper on halogen derivatives of polyacetylene that he co-authored in 1977 alongside Alan MacDiarmid and Alan Heeger – fellow laureates of the 2000 Nobel prize. This work initiated the emergence of polymer electronics and transformed circuit design.
Born in Tokyo in August 1936 to a physician and the daughter of a Buddhist temple chief priest, Shirakawa’s family relocated several times during his youth. In 1944, they eventually established their home in the quaint city of Takayama.
Takayama, nestled in a basin encircled by mountains with a river meandering through it, provided a backdrop for Shirakawa’s childhood interests in collecting insects and plants, as well as building radios. “My passion for science was ignited and flourished during those 10 years,” Shirakawa reflected in a biography for the Nobel prize.
When reminiscing about his aspirations as a teenager, he expressed a desire to become a scientist in the future and to investigate plastics that would benefit everyday people.
A childhood foreboding resurfaces
After fearing that this essay had been misplaced, Shirakawa was both surprised and pleased when numerous Japanese newspapers published it the day after his Nobel prize announcement in 2000.
Shirakawa’s path to the Nobel prize commenced with an undergraduate degree in polymer chemistry in 1961 at the Tokyo Institute of Technology – presently known as the Institute of Science Tokyo – after contemplating studies in horticulture and electronics. He continued his education at the university, obtaining a PhD in engineering in 1966. That same year, he wed his wife, Chiyoko Shibuya, and took on the role of research associate at the institute. Initially, he concentrated on deciphering the polymerization mechanism of polyacetylene utilizing Ziegler–Natta catalysts.
However, in 1974, a visiting scientist in Shirakawa’s lab mistakenly added an excessive amount of Ziegler–Natta catalyst to acetylene, resulting in the formation of irregular pieces of a mysterious silvery film of polyacetylene instead of the anticipated black powder.
Concurrently, at the University of Pennsylvania, MacDiarmid and Heeger were captivated by recent findings on polymeric sulfur nitride that demonstrated electrical properties. They opted to collaborate in order to comprehend this peculiar polymer.
Serendipitously, MacDiarmid delivered a talk at the Tokyo Institute of Technology on polymeric sulfur nitride in 1974. Following the lecture, he conversed with Shirakawa about their shared enthusiasm for conductive materials over tea.
A promising collaboration in Pennsylvania
Shirakawa presented him with a sample of the silvery, aluminum foil-like film created in his lab, and MacDiarmid invited him to the University of Pennsylvania to further investigate conductive polymers with both Heeger and himself. Shirakawa embraced the opportunity and relocated to Pennsylvania in 1976, spending a year there. Together, the three demonstrated that it was feasible to produce conductive polymers composed of a carbon chain with alternating single and triple bonds, which were subsequently doped with a halogen.
Shirakawa vividly recounted how he and C K Chiang, a postdoctoral fellow in Heeger’s lab, were assessing the electrical conductivity of polyacetylene in 1976. “At the exact moment we introduced bromine, the conductivity surged so quickly that he couldn’t adjust the range of the electrometers,” he reminisced. The conductivity of polyacetylene escalated 10 million times after doping with bromine.
Following the publication of Shirakawa’s Nobel prize-winning paper with Heeger and MacDiarmid in 1977, he transitioned to the University of Tsukuba in 1979, where he remained for the duration of his career.
MacDiarmid passed away in early 2007 while Heeger, now 90, is a professor emeritus at the University of California, Santa Barbara, and continues to be active in research.
Nurturing future generations
Upon hearing of Shirakawa’s death, Yujiro Tanaka, president and chief academic officer at the Institute of Science Tokyo, highlighted not only his scientific accomplishments but also his role as a mentor. “Once a year, the professor dedicated time to deliver a one-hour lecture followed by a thirty-minute question-and-answer session with students,” Tanaka noted. “The auditorium was consistently full, and those unable to find a seat would stand along the walls.”