Mixed electron and proton conductivity of polyaniline films in aqueous solutions of acids: beyond the 1000 S cm⁻¹ limit

Abstract

BACKGROUND: The application potential of conducting polymers depends on their conductivity. It is generally assumed that the conductivity determined in the dry state is a parameter that unambiguously characterizes them.RESULTS: The conductivity of polyaniline (PANI) films immersed in aqueous solutions of sulfuric acid may be more than 1000 times higher compared with that obtained by measurement of dry films in air, and is estimated to reach a value exceeding 3300 S cm−1 in 1 mol L−1 sulfuric acid. This is explained by the reduction of conductivity barriers between conducting PANI islands.CONCLUSION: The organized polymer chains in the conducting islands of a PANI film are separated by disordered regions of low conductivity in the dry state. The penetration of sulfuric acid solution into the disordered areas increases the overall conductivity of the PANI film by improving the electrical contact between the islands through ionic charge transport. The electronic conductivity of the PANI film in the dry state thus converts to mixed electron–proton conduction in acidic aqueous solutions, electron conductivity being dominant in ordered regions and ionic conductivity in disordered regions separating them. Weakly bound protons are the most important ionic charge carriers hopping along the PANI chains. Copyright © 2009 Society of Chemical Industry

Surface and proton conductivity properties of electrospun poly(vinyl butyral)/polyaniline nanofibers

“…[37,38] Its proton conductivity was modeled by Stejskal et al [38] In its protonated form, the free hydrogens on the imine sites of PANI can hop from one nitrogen to another allowing intra-and intermolecular hydrogen transportation. [37,38] Its proton conductivity was modeled by Stejskal et al [38] In its protonated form, the free hydrogens on the imine sites of PANI can hop from one nitrogen to another allowing intra-and intermolecular hydrogen transportation.…”

Large Enhancement in Conductivity of Polyaniline Films by Cold Stretching

“…[32] In the present work, after reprotonation of the stretched PANI films in HCl, the films were dried at about 30 8C in air for at least one day to allow HCl to evaporate before the measurement of electrical conductivity. Therefore, the ionic conductivity should have no contribution to the observed conductivity increase.…”

Electromechanical properties study of 1-butyl-3-methylimidazolium chloride/cellulosic gel blended with polydiphenylamine

“…However, electrical conductivity decreases when it is overdoped at acid:monomer >10:1 as PDPA particles become agglomerated and diminish the available surface area needed to transfer electrons. There is a synergism between ionic conductivity of CelGel (long-range movement of BMIM + cations [49] and protons) and the electronic-ionic mixed conductivity of dPDPA (polarons and acid protons) [48], whose maximum electrical conductivity is 20.81 S/cm at the 10:1 doping level. High electrical conductivity may also be attributed to the promotion of proton conductivity via the N H bonding of the dPDPA secondary amine as previously mentioned.…”

“…The electrons in the protonated PDPA structure may become delocalized and produce polarons, which are the charge carriers responsible for the electronic conductivity of PDPA. Simultaneously, the chemical structure of a protonated imine site in PDPA represents a typical proton-conducting unit [48]. However, electrical conductivity decreases when it is overdoped at acid:monomer >10:1 as PDPA particles become agglomerated and diminish the available surface area needed to transfer electrons.…”