Synthesis and characterization of soluble polypyrrole doped with alkylbenzenesulfonic acids

Soluble polypyrrole (PPy) was chemically synthesized in the presence of a series of alkylbenzenesulfonic acid (ABSA) dopants. The higher conductivity of PPy doped with short alkyl chain dopant might be due to the short range ordering of PPy chains. This result was confirmed by UV/VIS/NIR spectroscopy, which suggested that the high conductivity resulted from more delocalized electrons and higher concentration of bipolaron. The sharp small angle diffraction peaks for PPy doped with dodecylbenzenesulfonic acid (DBSA) indicated that the long alkyl chain of DBSA acted as a spacer between polymer chains and induced layered structure with the highest d-spacing of 26.4degrees The layered structure of PPy/DBSA was responsible for its notable solubility even if all PPy/ABSA powders were soluble at the polymerization conditions used. When the monomer-to-oxidant ratio, [Mo]/[Ox], was ranged from 2.5 to 15 for PPy doped with DBSA, the lower conductivity at low oxidant concentration might be associated with the lower molecular weight because FTIR study implied that the decreased conductivity was related to the shorter conjugation length. In PPy/DBSA powders, the best compromise between electrical conductivity and solubility was found to be at [Mo]/[Ox] = 7.5 for m-cresol. (C) 2003 Elsevier B.V. All rights reserved.