Thermal stability and structure of electroactive polyaniline-fluoroboric acid-dodecylhydrogensulfate salt

Oxidation of aniline by emulsion polymerization pathway using benzoyl peroxide oxidant in the presence of fluoroboric acid and sodium lauryl sulfate surfactant leads to incorporation of both acid group as well as surfactant group onto the polyaniline chain as dopants i.e. formation of polyaniline-fluoroboric acid-dodecylhydrogensulfate salt (PANI-HBF4-DHS). Amount of dopants such as fluoroboric acid (HBF4), dodecylhydrogensulfate (DHS) and water present in the PANI-HBF4-DHS was found out for the first time. Electrochemical activity and rheological stability of the polymer were determined. Thermal stability of PANI-HBF4-DHS was determined by subjecting the polyaniline salt in macroscale at four different temperatures (100, 150, 200 and 250 °C). Structure, composition and thermal stability of polyaniline salt were determined by chemical analysis, conductivity, IR, UV/vis, XRD spectral measurements from the heat treated samples. Polyaniline salt contains 8.3 wt% water, 22.4 wt% HBF4 and 15.4 wt% DHS at ambient temperature. Upon vacuum, polyaniline salt loses 4.7 wt% water and on heating the sample at 100 °C it loses the remaining 3.6 wt% water. On further heating polyaniline salt loses its dopants and at 250 °C it loses both the dopants almost completely. Polyaniline salt on heating undergoes cross-linking even at 100 °C and however, conductivity (3 × 10−2 S/cm) of polyaniline salt was found to remain almost the same up to 150 °C.