The frequency-dependence conduction of polyaniline based on their para-crystalline structures

Nano-sized polyanilines (PANIs) doped with different protonated acids, HCl, H2SO4 and HNO3, were synthesized by the interfacial polymerization, and they displayed the form of emeraldine, which was a half oxidation form obtaining semi-conductivity. The structural characterizations of FT-IR demonstrated PANI doped with HNO3 (PANI-HNO3) obtained highest oxidation, and those of X-ray diffraction showed a disordered structure with poor packing and enlarged d-spacing distance in PANI-HNO3. The spectroscopy of electrical conductivity and dielectric was used to illuminate the charge transport mechanism in PANI para-crystallines, as well as the structural features affected by the doping acids. Based on the analysis of microscopic conduction contributions, the establishment of an equivalent circuit and the corresponding mathematical computational fitting for the plots of the complex impedances, AC conductivity and electric modulus, there showed in PANI-HNO3 lower value of fitting parameter α in the Constant Phase Element (CPE) model and more modulus losses, compared with PANIs doped with HCl or H2SO4. It indicated that the inter-chain hopping conduction in PANI-HNO3 was difficult due to the structural defects caused by the strong oxidation effect of HNO3 and the large spacing distance among the polymer chains.