Polythiophene

Polythiophene

Polythiophenes (PTs) result from the polymerization of thiophenes, a sulfur heterocycle, that can become conducting when electrons are added or removed from the conjugated π-orbitals via doping.

The study of polythiophenes has intensified over the last three decades. The maturation of the field of conducting polymers was confirmed by the awarding of the 2000 Nobel Prize in Chemistry to Alan J. Heeger, Alan MacDiarmid, and Hideki Shirakawa “for the discovery and development of conductive polymers." The most notable property of these materials, electrical conductivity, results from the delocalization of electrons along the polymer backbone – hence the term “synthetic metals”. However, conductivity is not the only interesting property resulting from electron delocalization. The optical properties of these materials respond to environmental stimuli, with dramatic color shifts in response to changes in solvent, temperature, applied potential, and binding to other molecules. Both color changes and conductivity changes are induced by the same mechanism—twisting of the polymer backbone, disrupting conjugation—making conjugated polymers attractive as sensors that can provide a range of optical and electronic responses.

A number of comprehensive reviews have been published on PTs, the earliest dating from 1981. Schopf and Koßmehl published a comprehensive review of the literature published between 1990 and 1994. Roncali surveyed electrochemical synthesis in 1992, and the electronic properties of substituted PTs in 1997. McCullough’s 1998 review focussed on chemical synthesis of conducting PTs. A general review of conjugated polymers from the 1990s was conducted by Reddinger and Reynolds in 1999. Finally, Swager et al. examined conjugated-polymer-based chemical sensors in 2000. These reviews are an excellent guide to the highlights of the primary PT literature from the last two decades.