The π–π interaction induced secondary doping in conducting poly-3-alkylthiophenes

A new driven force of the secondary doping in polyalkylthiophene was reported. It was found that the mechanism of secondary doping in polyalkylthiophene was mainly due to the π–π interaction between the secondary dopant and the thiophene rings in polymer backbone. The secondary dopant altered the conformation of polymer chains from coiled to expanded form by π–π interaction induced face-to-face interchain stacking as well as dissolution and rearrangement of the alkyl side chains. Upon treating with secondary dopant, the intensity of bipolaron band, the IR reflectance, and the crystallinity of the polymer films all increased. Therefore, the conductivity of the AuCl3-doped polyalkylthiophene films increased two times after being secondarily doped with benzene.