Electropolymerization in a novel proton functionalized room temperature ionic liquid anilinium acetate

•A novel proton functionalized RTIL–anilinium acetate is synthesized.•Electrosynthesis of PANI in [HANI]Ac runs at low onset potential and high rate.•Charge balancing counter-ion influences the anilinium oxidation onset potential.•The diffusion of PANI results in different CV signals under different conditions.•Triethylamine can tune the H+ level for the polymerization and therefore the rate.

A novel proton functionalized room temperature ionic liquid–anilinium acetate ([HANI]Ac) with high ionic conductivity and low viscosity has been synthesized and used for the first time for aniline electropolymerization without any additives. The electropolymerization process reveals that the onset potential for anilinium oxidation (Eonset) in neat [HANI]Ac is +0.45 V vs. SCE, which is lower than those in aqueous and nonaqueous (ionic liquid as solvent/electrolyte) solutions. The control experiments and theoretical calculations indicate that the low Eonset in neat [HANI]Ac should be attributed to charge balancing counter-ion Ac−. Compared with [HANI]Ac/[BMIM]PF6 binary system, the mass transfer resistance of anilinium in neat [HANI]Ac is small, therefore the electropolymerization can be kept on at a high rate in a period. The cyclic voltammograms and Fourier transform infrared spectra demonstrate that the obtained PANI is highly conductive. The PANI has moderate solubility in [HANI]Ac and its adherence to the electrode is poor. During the electropolymerization, the accumulated PANI diffuses from the electrode/solution interface to the bulk phase which leads to different current signals of PANI under different conditions. Stirring slightly increases the oxidation current signal of anilinium but greatly reduces the redox current signal of PANI. Under quiescent conditions, lowering the upper switching potential reduces the redox current signal of PANI. The potential scan rate has great effect not only on the current signal of PANI but also on the redox peak shape. The electropolymerization process of [HANI]Ac in the presence of triethylamine further demonstrates that proton deficiency can result in a significant reduction of the rate of aniline polymerization.

Graphical abstractA novel proton functionalized room temperature ionic liquid anilinium acetate is synthesized and used for aniline electropolymerization without any additives.Figure optionsDownload full-size imageDownload as PowerPoint slide