Charge transport and dielectric relaxation processes in aniline-based oligomers

• Aniline-based oligomers were synthesized by oxidation of aniline with p-benzoquinone in the solutions of methanesulfonic acid.
• Electrical conductivity increased in strongly nonlinear fashion with acid concentration.
• Significant difference in electrical properties of lowly and highly protonated oligomers was observed.
• Depending on protonation level different relaxation processes were observed.
• Relaxations are related to charge transport, interfacial polarization and dipole orientation.

The aniline-based oligomers were synthesized by oxidation of aniline with p-benzoquinone in the solutions of methanesulfonic acid, 2,5-dianilino-p-benzoquinone methanesulfonate salt being the main product. The synthesized samples were characterized by UV–visible and FTIR spectroscopies and compared with polyaniline base. In order to characterize the electrical properties of materials obtained, the conductivity measurements and broadband dielectric spectroscopy were performed. The dependence of DC conductivity on the acid concentration in the reaction medium was strongly non-linear (percolation-like) thus indicating a significant difference in electrical properties of lowly and highly protonated aniline-based oligomers. This difference is confirmed by dielectric properties exhibiting one common (dipole orientation polarization) and two specific (charge carrier hopping and interfacial polarization) relaxation processes.