Electropolymerization of p-anisidine: influence of pH on electrosynthesis

Abstract

The electropolymerization of p-anisidine on graphite electrodes (GE) was investigated in acidic and basic media using cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), electrochemical impedance spectroscopy (EIS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM). The results showed significant differences in the polymer formation between the two media. In acidic media, a more electroactive but less stable material is deposited on the electrode surface, whereas the polymer formed in basic media exhibits high resistivity. The CV of the ferricyanide solutions highlighted these differences compared to the unmodified electrode, with an increased current for the acidic polymer and an almost non-existent redox response for the basic polymer. The EIS data corroborated the voltammetry results, revealing significant differences between the resistance values of the two polymers. The charge-transfer resistance increased with increasing pH, indicating slow electron-transfer kinetics. The SEM images show important differences between the graphite electrode and modified electrodes, suggesting the formation of distinct polymer films. ATR-FTIR spectra indicated polymer formation involving nitrogen atoms, with the methoxy group remaining unchanged. Based on electrochemical and spectroscopic evidence, a polymerization mechanism was proposed, involving the formation of tertiary amines in the polymer backbone. The irregular structure of the polymer formed in basic media can explain its resistive behavior. These findings contribute to the understanding of p-anisidine electropolymerization and development of polymer-modified electrodes for potential biosensor applications.

Graphical abstract