A Direct One-pot Method for Synthesis of Polyaniline Doped with Dodecyl Benzene Sulphonic Acid in Aqueous Medium and Study of its Thermal Properties

POlyaniline (PANI) doped with dodecyl benzene suiphonic acid (OBSA) was directly synthesized by aniline polymerization in the presence of OBSA in an aqueous medium. The temperature and colour changes of the polymerization reaction were carefully recorded and found that the polymerization of aniline begins after 80 min with changing reaction colour from white to pale blue. Fourier transform infrared (FTIR), elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (OSC) and X-ray diffraction (XRO) techniques were used to characterize and analyze the thermal characteristics of the doped PANI sample. In the FTIR spectrum, the peak related to NW...S03 interactions between the polymer chain and the dopant appeared at 1026 cm,1. The obtained TGA curve has illustrated three major stages in the weight loss of the doped PANI. These three weight loss stages were accounted to the evaporation of moisture, evaporation of OSSA, and the chemical structure degradation of PANI. The moisture, OBSA, and PANI contents of the product were calculated from TGA curve and it was shown that approximately 6.65 aniline repeating units have been doped with one OBSA molecule. The ose thermogram has shown two endothermic peaks around 1200e and 2800e due to the evaporations of moisture and OBSA, respectively. The analysis of XRO spectra confirmed that a chemical cross-linking reaction occurs between the PANI chains during thermal treatment and increases the amorphous state of the sample. The resultant electrical conductivity examination at the heating temperature of 1000e has shown that at the heating time of 30 min the doped PANI possessed maximum electrical conductivity which decreased by increase in heating time.