ABSTRACT
Ever since the discovery of metallic conductivity in iodine-doped polyacetylene in the 1970s, conducting polymers have been at the forefront of scientific interest and research. The ability to achieve metal-like conductivities in materials that are traditionally accepted as insulating plastics ushered in the ‘organic electronics’ era, and this discovery was recognized with a Nobel prize to Heeger, MacDiarmid, and Shirakawa in 2000. 1 – 3 Poor stability of the conducting form of polyacetylene in air due to oxidation of its free-radical ions motivated early research towards finding more stable counterparts. 1 , 4 , 5 Polyaniline (PANI) is one of the most widely studied conducting polymers; its proton-doping mechanism makes PANI’s conducting form more resilient to oxidation compared to polyacetylene. 6 , 7 Although PANI’s exact polymeric structure was unknown at the time, its electrochemical properties were first described more than a century ago. 8 Reports of charge transport in its half-oxidized state ensued in the 1960s. 9 In the 1980s, extensive studies were conducted on PANI’s charge-transport properties, and conductivities exceeding 400 S cm−1 were accessed in hydrochloric acid (HCl)-doped PANI that is exposed to secondary dopants. 10 , 11 In the same era, researchers at Bayer focused on thiophene-based conducting polymers and discovered an oxygen-substituted derivative of polythiophene, poly(3,4-ethylenedioxythiophene), or PEDOT, as another alternative to polyacetylene. 12 , 13 Although there have been other successful conducting polymers, such as polypyrrole and polythiophenes, that have found use in many different applications, this chapter will mainly focus on PANI and PEDOT due to their pervasiveness.
