Characterization of picric-acid-doped poly(o-toluidine) and the picric-acid-doped poly(o-toluidine)-induced conductive composite of acrylonitrile–butadiene–styrene

Poly(o-toluidine) (POT) in emeraldine base form (EB) has been doped with picric acid (PA-doped POT) and dinitrophenol (DNP-doped POT). The conductivities of these doped polymers were found to be 10.52 and 4.82×10−3 S cm−1, respectively. The large difference in conductivity of these polymers is attributed to the more acidic nature of picric acid (PA) than dinitrophenol (DNP). The disappearance of the peak at ∼650 nm due to EB and the presence of the peak at ∼850 nm due to localized polaron in the absorption spectra clearly reveal the dopant-induced protonation of POT. This is also supported from the XPS spectrum showing the disappearance of the peak at ∼398.2±0.1 eV due to the imine nitrogen component in EB and the appearance of the peak at ∼402.16±0.1 eV owing to the iminium ion (NH+) of PA-doped POT.The PA-doped POT is thermally stable up to 140°C and completely dedoped at ∼300°C. The mass spectra recorded simultaneously with the thermal weight loss showed several fragments due to the decomposition of PA in the temperature region from 140°C to 300°C. The observed high conductivity of PA-doped POT film is attributed to the expanded coil-like conformation, which was proven with the help of the reduced viscosity measurement. The composite of PA-doped POT with insulating acrylonitrile–butadiene–styrene copolymer (ABS) was prepared, and the percolation threshold for this composite was ∼3 wt.%, which was considerably low compared to that for a typical composite, e.g., ∼16 vol.% for poly(3-alkylthiophenes) (P3ATs)/polystyrene (PSt) composite.