Several protic ionic liquids based on trifluoroacetate anion and different alkylammonium (diethyl-, dimethylethyl-, tributyl-, diisopropylethyl-) cations have been synthesized and investigated by different methods. Based on the results obtained earlier for triethylammonium and triethanolammonium trifluoroacetates, the influence of the cations structure on the thermal (phase transition and decomposition temperatures) and electrochemical (conductivity, electrochemical window, ionicity) properties of the PILs has been studied. For the investigated salts, the specific conductivity within the cation series DMEA > DEA > TEA > TBA decreases. These PILs have been used as dopants to prepare membranes based on (poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP)) whose electrochemical and thermal properties have also been investigated. The electric conductivity of these membranes was lower than that of the PILs themselves because of the confined mobility of the ions. However, the conductivity decrease was not too significant and did not exceed one order of magnitude. Doping PILs into the PVdF-HFP copolymer lowered the polymer crystallinity degree. The values of the electrochemical window of the studied PILs and PVdF-HFP–PILs membranes ranged from 0.9 to 1.3 V and from 6 to 7 V, respectively.
