Thermoreversible gels of polyaniline: Viscoelastic and electrical properties

We demonstrate that polyaniline (PANI) dissolved in dodecyl benzene sulphonic acid (DBSA) shows thermoreversible gelation. The dissolution has been performed in formic acid which allows particle-free complexes according to optical microscopy. Below the gelation temperature the materials are rubber-elastic in compression experiments, the storage modulus G' does not essentially depend on frequency, and the samples are electronically conductive. Above the gelation temperature, G' indicates flow-like behavior and drastically lower ionic conductivity is observed. These results suggest reversible, i.e. fusible, network formation. The properties are compared with gels consisting of camphor sulphonic acid (CSA) doped PANI dissolved in nr-cresol which are poorly thermoreversible.