Synthesis and electrochemical modulation of the actuator properties of poly(phenazine-2,3-diimino (pyrrol-2-yl))

Abstract

A novel Schiff- base compound, phenazine-2,3-diimino(pyrrol-2-yl), was chemically synthesized by the condensation reaction of 2,3-diaminophenazine and pyrrole-2-carboxaldehyde and its structure confirmed by FTIR, NMR and SEM. Poly(phenazine-2,3-diimino(pyrrol-2-yl)) (PPDP) doped with 1,2- naphthaquinone-4-sulfonic acid (NQSA) was then electrochemically synthesized on a glassy carbon electrode in 0.1M HCl. Electrochemical impedance spectroscopy (EIS) was used to assess the actuating mechanism of PDPP by investigating the change in film thickness in various aqueous media, i.e. 0.1M NaCl, HCl, KCl and CaCl3, at the reduction potential. Surface analysis of the synthesized polymer, were also done on screen printed carbon electrodes to investigate its morphology. Cyclic Voltammetry showed two redox couples, i.e. a quasi- reversible couple due to the pyrrole moiety and an irreversible couple due to phenazine’s electrochemistry, with a surface concentration of 1.89x10-9mol.cm2 , a diffusion coefficient of 4.61x10 -7cm2 .s-1 and a rate constant of 1.48x10-3cm.s1 . Osteryoung Square Wave Voltammetry gave a formal potential of +320 mV vs Ag/AgCl. The trend in film thickness (as determined from EIS) for the different solvents were KCl>CaCl2>NaCl>HCl, which is attributed to the increase in the cationic radius of the charged species. The film thickness of PPDP/NQSA at +320mV in 0.1M HCl was found to be 1.007μm, which increased by 0.023μm at the reduction potential in the same solvent. Polypyrrole doped with NQSA showed a change of 0.012 μm under the same conditions.