A Short History of the PEDOT Invention

Soon after the discovery of conducting polyacetylene attempts to utilize these exciting new compounds in technical applications started. Bayer s Central Research Department also initially focused on polyacetylenes beginning as early as 1980. Several promising attempts to stabilize polyacetylene in its highly doped form and to achieve processability ultimately failed. As a result, Bayer rather promptly decided to abandon this research direction. Attempts to utilize polyacetylene in polarizers several years later failed commercially. 

A bit of work on conductive tetracyano-quinodimethan complexes followed, but a major technical or even commercial breakthrough was not achieved. A few other charge-transfer complexes were investigated to a limited extent, but they also were not commercialized successfully by Bayer AG.  

Therefore the polycondensates workgroup within the Bayer Central Research Department started several projects regarding polyheterocycles in the second half of the 1980s. First, work was focused on polypyrrole, particularly for antistatic layers on thermoplastics like polycarbonate (molded parts or sheets). After less than two years, the Bayer workgroup was forced to terminate these activities by the intrinsic drawbacks of polypyrrole, like toxicity and high vapor pressure of the monomer, and the intense color and poor transparency of polypyrrole layers itself. 

A lot of poly(3-alkyl-thiophenes) were known at that time, and some of these special polythiophenes exhibited a remarkable conductivity in the doped state. A comprehensive overview about polythiophenes and their electronic properties available at that time can be foimd in the Handbook of Oligo- and PolythiophenesP The fundamental drawback of all these polythiophenes was the instability of the highly conductive form. In particular, humid air was destructive. 

Radical cation (polaron) mesomeric stabilization with oxygen contribution. 

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