Preparation and Properties of Polyaniline Codoped with Ionic Liquid and Dodecyl Benzene Sulfonic Acid or Hydrochloric Acid

Three nanosized polyaniline (PAn) powders doped with ionic liquid and dodecyl benzene sulfonic acid (DBSA) or hydrochloric acid have been prepared for the first time in an ionic liquid-water emulsion system. The oil-phase ionic liquid is used as both a monomer solvent and doped counterion. The effects of different counterions on the properties (molecular weight, electrical conductivity, glass transition temperature, electrochemical activity) of PAn are investigated. PAn codoped with 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and DBSA shows the highest molecular weight (81 104 g mol−1), the highest electrical conductivity (1.85 S cm−1), the lowest glass transition temperature (181°C) and the highest redox reaction current density; PAn doped with an ionic liquid only exhibits the lowest conductivity (0.0018 S cm−1) and a lower redox reaction current density. PAn codoped with ionic liquid and HCl shows higher conductivity. They also exhibit good electrochemical stability and charge-discharge performance. These indicate that codoping of different counterions under acidic conditions could improve the degree of oxidation and doping ratio of PAn and could result in high electrical conductivity and good electrochemical properties.