Electropolymerization in proton-functionalized anilinium salts/glycol deep eutectic solvents

Novel proton-functionalized solid anilinium salts (anilinium hydrochloride ([HANI]Cl) and anilinium nitrate ([HANI]NO3)) are synthesized. Simply mixing proton-functionalized anilinium salt with glycol in appropriate ratios can get deep eutectic solvents (DESs) which are liquid at room temperature. DES system is a new type of ionic liquids (ILs) or IL analogs. Tests show that the resulting DES systems have higher conductivity and lower viscosity which are suitable for electropolymerization. The electropolymerization of aniline in novel liquid DES ([HANI]Cl/(CH2OH)2 and [HANI]NO3/(CH2OH)2) without exogenous protons is first reported. The cyclic voltammograms (CVs) in neat DES show two pairs of redox peaks. Unlike in acidic aqueous solutions, the electropolymerization of aniline in the DES needs no exogenous protons. UV–Vis and FTIR analysis show that the conductive polyaniline (PANI) is obtained. Moreover, the specific capacitance of PANI from the [HANI]Cl/(CH2OH)2 system is ca. 341 F g−1 and that from the [HANI]NO3/(CH2OH)2 is ca. 492 F g−1, which are superior to that of the PANI obtained in an acid medium. The SEM characterization indicates that the resulting PANI on ITO is cross-linked nanoporous polymer membrane, which is benefit for the capacitance performance of PANI.