A novel conducting soluble polypyrrole composite with a polymeric co-dopant

Electrically conducting polypyrrole (PPy)/polymeric dopant composites were chemically synthesized in an aqueous solution containing dodecylbenzene sulfonic acid (DBSA) as a dopant, poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) as a co-dopant, and ammonium persulfate (APS) as an oxidant. The PPy composites were soluble in chloroform when an extra amount of DBSA was added to the solvent. Chemical composition and doping level of the PPy composite were determined by XPS and the elemental analysis. We found that PAMPS was incorporated into the PPy composite as the co-dopant and that the content of PAMPS in the composite increased with the amount of the PAMPS fed in the polymerization solution. Nevertheless, the overall doping level of the PPy composite was estimated to be about 25% regardless of the feed ratio of the dopants. The electrical conductivity of the PPy composite (PPy/DBSA/PAMPS) cast film doped with DBSA and PAMPS was close to that of PPy film (PPy/DBSA) doped with only DBSA. Although PPy/DBSA/PAMPS showed a little worse thermal stability in air than PPy/DBSA, the PPy/DBSA/PAMPS composites exhibit excellent mechanical properties compared with other PPys synthesized chemically or electrochemically. We believe that the improved mechanical properties result from the long chain characteristics of the polymeric co-dopant in the composite.