Polymers have always been considered as being very good insulators of electricity. However around thirty years ago no one would have believed that polymers have the potential to conduct just as well as metals. But since then such accomplishments have been achieved through simple modifications of organic conjugated polymers. These new polymers are called electrically conducting polymers or synthetic metals’, they combine the electrical properties of metals with the array of advantages that polymers possess. These advantages include lighter weight, greater workability, resistance to corrosion and chemical attack as well as cost effectiveness.
Dr H. Letheby was the first person to initiate the study of conducting polymers. In the year 1862 he first attempted to investigate the behaviours of chemical reactions and to select them accordingly from his findings. This developed his study of electro polymerised aniline sulphate to being published in the journal of chemical society. The results showed that aniline sulphate formed a blue-ish black solid layer on a platinum electrode after its polymerisation.
The first of their kind highly conductive organic compounds were charge transfer complexes. During the 1950’s researchers conveyed polycyclic aromatic compounds formed semi conducting charge transfer complex salts when combined with halogens. In the early 1970’s researchers exhibited how salts of tertrathiafulvalene display practically metallic conductivity, whilst superconductivity was demonstrated in 1980. Despite these compounds not technically being polymers, this indicated to other scientists organic compounds do have the capability of carrying current and that too efficiently.
The first major breakthrough of electrically conducting polymers was in 1978 when demonstrated by Alan Heeger, Alan Macdiarmid and Hideki Shirakawa, that polyacetylene (PA), an intrinsically insulating organic conjugated polymers showed a great increase in electrical conductivity on treatment with oxidizing (electron-accepting) or reducing (electron donating) agents.
These oxidation and reduction reactions, which induce high conductivity in PA are termed as p-doping and n-doping respectively. During the early 1970’s Shirakawa was able to control proportions or cis and trans isomers in the reaction to produce polyacetylene. Then by an accident a thousand fold catalyst was added to the reaction by mistake producing a silver film of trans polyacetelyene and copper film of cis polyacetylene. Despite these films having a metallic look they were still not conductive. Independently from Shirakawa, MacDiarmid and Heejer were experimenting with another metallic looking polymer, sulphur nitride (SN)X.
The three met at a coffee break at a seminar in Tokyo and discussed their work eventually leading to their collaborative work. In the year 2000 Dr Alan Heeger, Hideki Shirakawa and Alan Macdiarmid were awarded the Nobel prize in chemistry for the discovery and development of conductive polymers. This huge breakthrough has led to many other conjugated polymers being studied including polypyrolle, polythiophene and polyphenylenevinylene, As well as polymers being used in OLEDS which is an LED using conductive polymers which emit light under voltage and organic solar cells which use the polymers to convert photons into a current. Furthermore, there are many current and potential uses of conductive polymers and this all down to the three individuals research work that earnt them the nobel prize