Hideki Shirakawa (白川 英樹, Shirakawa Hideki; August 20, 1936 – August 24, 2026) was a Japanese chemist and engineer who was Professor Emeritus at the University of Tsukuba and Zhejiang University. He was best known for his discovery of conductive polymers. He was co-recipient of the 2000 Nobel Prize in Chemistry jointly with Alan MacDiarmid and Alan Heeger.
Hideki Shirakawa was born in Tokyo, Japan, on August 20, 1936, the second son of a military doctor. He was the third of five children. Olympic marathoner champion Naoko Takahashi is his second cousin-niece. He lived in Manchukuo and Taiwan during childhood. Around third grade, he moved to Takayama, Gifu, which is the hometown of his mother.
Shirakawa graduated from the Tokyo Institute of Technology (Tokyo Tech) with a bachelor's degree in chemical engineering in 1961, and his doctorate in 1966. Afterward, he obtained the post of assistant in the Chemical Resources Laboratory at Tokyo Tech.
While employed as an assistant at the Tokyo Institute of Technology (Tokyo Tech) in Japan, Shirakawa developed polyacetylene, which has a metallic appearance. This result interested Alan MacDiarmid when MacDiarmid visited Tokyo Tech in 1975.
In 1976, he was invited to work in the laboratory of Alan MacDiarmid as a post-doctoral fellow at the University of Pennsylvania. The two developed the electrical conductivity of polyacetylene along with American physicist Alan Heeger.
In 1977 they discovered that doping with iodine vapor could enhance the conductivity of polyacetylene. The three scientists were awarded the Nobel Prize in Chemistry in 2000 in recognition of the discovery. With regard to the mechanism of electric conduction, it is strongly believed that nonlinear excitations in the form of solitons play a role.
In 1979, Shirakawa became an assistant professor in the University of Tsukuba; three years later, he advanced to a full professor. In 1991 he was appointed chief of the Science and Engineering Department of Tsukuba's Graduate School (until March 1993), and chief of Tsukuba's Category #3 group (until March 1997).
On August 24, 2026, Shirakawa died at a hospital in Yokohama, Japan, at the age of 90.
According the University of Tsukuba's web page on Shirakawa, his research on conductive polymers can be broken down into four main categories: polyacetylene thin film synthesis, the causation of metallic conductivity due to chemical doping, the creation of conjugated (double or triple bonds in a molecule which are separated by a single bond) liquid crystalline polymers, and acetylene polymerization development that used liquid crystals as solvents.
Polyacetylene Synthesis: Polyacetylene was expected to have certain properties, with insolubility making the substance difficult to work with. Dr. Shirakawa found that polyacetylene thin films can be synthesized, and with the thin films, the doctor clarified the molecular and solidified structures of polyacetylene.
Creation of Metallic Conductivity: Dr. Shirakawa found that, when a trace of a halogen such as bromine or iodine is added to thin film polyacetylene, its electric conductivity increases, and it exhibits metallic conductivity. Shirakawa found that partial electron transfer between dopants and p-electrons of polyacetylene can generate metallic conductivity.
Using Liquid Crystals to Develop Acetylene Polymerization: Dr. Shirakawa developed a method for the production of highly conductive polyacetylene thin films which paralleled the polymerization of acetylene. Furthermore, he succeeded in the synthesis of thin films of helical polyacetylene whose chirality is controllable.
'Chirality: a property of asymmetry, meaning a molecule is distinguishable from its mirror image; that is, it cannot be superimposed onto it
Creation of Conjugated Liquid Crystalline Polymers: Dr. Shirakawa created self-oriented, conjugated liquid crystalline polymers by introducing liquid crystalline groups into the side chains of p-conjugated polymers such as polyacetylene. He also macroscopically oriented the polymers with electric or magnetic fields and succeeded in having the molecules electric anisotropy.
The general definition of electrical anisotropy describes the variation of an electrical property depending on the lateral or vertical direction (x,y,z) in which a current flows.
1983 – The Award of the Society of Polymer Science, Japan
2000 – SPSJ Award for Outstanding Achievement in Polymer Science and Technology
2000 – Nobel Prize in Chemistry