Thermal studies of polyaniline doped with dodecyl benzene sulfonic acid directly prepared via aqueous dispersions

In this paper, polyaniline (PANI) doped with dodecyl benzene sulfonic acid (DBSA) was directly prepared by chemical oxidation in aqueous dispersions. The temperature and color changes of the polymerization reaction solution were examined. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to analyze thermal characteristics of the doped PANI (PANDB). These results indicated that the PANDB powder had discernible moisture content. Moreover, in the first run of DSC thermal analysis, two endothermic peaks were found. The first endothermic peak (at around 120 degreesC) represented the evaporation of moisture. The second endothermic peak (at around 280 degreesC) represented the starting evaporation of DBSA. The XRD examination further confirmed the chemical crosslinking reaction during thermal treatment. The TGA result illustrated that there were three major stages for weight losses of the PANDB powder sample. The first weight loss at the lower temperature resulted from the evaporation of moisture. The second weight loss at the higher temperature was due to evaporation of DBSA. And the third weight loss at around 420 degreesC-450 degreesC was due to the chemical structure degradation of PANI. The electrical conductivity of PANDB has a plateau at the heating time around 30 min when the heating temperature was set at 100 degreesC.