Electrochemical and Spectroscopic Dynamics of Nanostructured Polynuclear Sulphonic Acid-Doped Poly(2, 5-dimethoxyaniline)

Abstract

Conducting and electroactive nanostructured poly(2, 5-dimethoxyaniline), PDMA, doped with anthracene sulphonic acid, ASA, and phenanthrene sulphonic acid, PSA, respectively, were prepared by oxidative polymerisation of 2, 5-dimethoxyaniline, DMA, with ammonium persulphate as oxidant. Scanning electron microscope, SEM, images of the polymers showed well defined nanotubes and fibrils with diameters of between 50 to 100 nm and 200 to 300 nm for PDMA-ASA and PDMA-PSA, respectively. Evidence of the incorporation of ASA and PSA into the PDMA backbone was provided by UV-Vis and FTIR analyses. Electrochemical interrogation of the sulphonic acid-doped polymers by cyclic voltammetry showed that both PDMA-ASA and PDMA-PSA exhibit quazi-reversible electrochemistry. The standard rate constant, ko, for the charge transfer reactions of PDMA-ASA and PDMA-PSA were 3.81 x 10-4 cm s-1 and 3.27 x 10-5 cm s-1, respectively. There was a relationship between the ko value and the formal potential, E0ʹ, of the polymeric nanomaterial. PDMA-ASA that had larger ko value gave an E0ʹ value of 134 mV which was lower than that of PDMA-PSA by 19 mV, indicating that PDMA-ASA has lower activation energy than PDMA-PSA for the electron transfer process Electrochemical impedance spectroscopy over a range of potentials showed that the polymeric nanotubues exhibited high conductivities, though the SA-doped polymer was more conducting.