Synthesis and characterization of polyaniline co-doped with nitric acid and dodecyl benzene sulfonic acid

Polyaniline (PANI) co-doped with nitric acid (HNO₃) and dodecyl benzene sulfonic acid (DBSA) was directly prepared by the chemical oxidative polymerization of aniline in an aqueous solution. When the molar ratio of HNO₃/DBSA was 0.3:7, the resulted co-doped PANI (PANI_H0.3D7) reached a maximum electrical conductivity of 7.98 S/cm. When the molar ratio of HNO₃/DBSA was 0.4:6, the resulted co-doped PANI (PANI_H0.4D6) exhibited a maximum yield of 70.09%. Thermogravimetric analysis (TGA) results illustrated that there were four weight loss stages in the co-doped PANI. These weight losses were resulted from the evaporation of moisture, HNO₃, DBSA, and PANI respectively. TGA results also indicated that approximately 10.04 and 3.32 repeating units of PANI were doped with one HNO₃ molecule and one DBSA molecule in the co-doped PANI_H0.3D7, respectively. Fourier transform infrared (FTIR) results showed that the absorption peaks of the −C═C− and −C_aromatic−N− stretching vibrations in the emeraldine salt (ES) PANI were all shifted to the lower wavenumbers than those in the emeraldine base (EB) PANI. It was worth noting that the morphology of PANI was strongly affected by polymerization conditions.