Hideki Shirakawa – discoverer of conductive polymers

Hideki Shirakawa – discoverer of conductive polymers

Category : Personalities
Published by : Data Research Analyst, Worldofchemicals.com

Biography & Contributions

Hideki Shirakawa is a Japanese chemist and Nobel laureate born on August 20, 1936. Shirakawa shared the prize with his research partners, the American physicist Alan Jay Heeger and the New Zealand-born American chemist Alan Graham MacDiarmid for discovery and development of conductive polymers. 

Shirakawa and associates serendipitously synthesized polyacetylene. In 1977 he began collaborating with MacDiarmid and Heeger at the University of Pennsylvania, where they exposed polyacetylene to iodine vapour. Their plan was to introduce impurities into the polymer much as in the doping process used to tailor the conductive properties of semiconductors. Doping with iodine increased polyacetylene’s electrical conductivity by a factor of 10 million, making it as conductive as some metals.

Conductive Polymer

Conductive polymers are organic polymers that conduct electricity. Conductive polymers are not thermoplastics but like insulating polymers, they are organic materials. They can offer high electrical conductivity but do not show similar mechanical properties to other commercially available polymers.

Conductive polymers are prepared by oxidative coupling of monocyclic precursors.The conductivity of these polymers is the result of the valence electrons are bound in sp3 hybridized covalent bonds.Conducting polymers have backbones of contiguous sp2 hybridized carbon centers.One valence electron on each center resides in a pz orbital, which is orthogonal to the other three sigma-bonds.All the pz orbitals combine with each other to a molecule wide delocalized set of orbitals.The electrons in these delocalized orbitals have high mobility when the material is doped by oxidation,which removes some of these delocalized electrons.Thus,the conjugated p-orbitals form a one-dimensional electronic band, and the electrons within this band become mobile when it is partially emptied.

Conductive polymer products with embedded and improved electromagnetic interference (EMI) and electrostatic discharge (ESD) protection have led to both prototypes and products.

Polyacetylene

Polyacetylene is an organic polymer with a long chain of carbon atoms with alternating single and double bonds between them, each with one hydrogen atom. It is an important polymer, as the discovery of polyacetylene and its high conductivity upon doping helped to launch the field of organic conductive polymers. Polyacetylene can be synthesized by ring-opening metathesis polymerization (ROMP) from cyclooctatetraene.

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