New dicationic piperidinium hexafluorophosphate ILs, synthesis, characterization and dielectric measurements

A new class of dicationic ionic liquids (ILs) were synthesized for electrochemical applications at high temperatures. The syntheses are based on a dialkylation reaction of N-alkylpiperidine followed by anion exchange. The structures of ILs, based on piperidinium combined with hexafluorophosphate anion, were identified by using 1H, 13C, 19F, 31P NMR and FT-IR spectroscopy. ILs’ thermal properties were investigated in the temperature range from −50 to 350 °C by using differential scanning calorimetry (DSC). In the frequency of 10−2–106 Hz range, dielectric measurements were performed on ILs’ samples at various temperatures from −80 to 20 °C, i.e. around the glass transition temperature. The peak relaxation was observed near to this temperature. Also, the conductivity was investigated and the energy activation determined. The temperature dependence of the relaxation times was shown to be governed by the Arrhenius equation.