Synthesis and properties of chemically coupled poly(thiophene)

We describe the synthesis and physical properties of poly(thiophene) with a molecular weight of approximately 4000 consisting of 46 - 47 thiophene rings (184 - 188 carbons along the backbone). The pristine polymer exhibits an ESR line similar to that of cis-(CH)_x; the small number of unpaired spins is consistent with relatively high-quality material. The electrical conductivity can be increased by nearly ten orders of magnitude to values in excess of 10 Ω^-1 cm^-1 upon partial oxidation by AsF₅. The magnitude and temperature dependence of the thermopower of the doped polymer (24 mol%) are consistent with metallic behavior. The decrease in conductivity as the temperature is lowered and the magnitude of π at room temperature apparently result from the macroscopic transport being limited by interparticle contacts.