N-methyl-N-alkylpyrrolidinium nonafluoro-1-butanesulfonate salts : Ionic liquid properties and plastic crystal behaviour

A series of <i>N</i>-methyl-<i>N</i>-alkylpyrrolidinium nonafluoro-1-butanesulfonate salts were synthesised and characterised. The thermophysical characteristics of this family of salts have been investigated with respect to potential use as ionic liquids and solid electrolytes. <i>N</i>-Methyl-<i>N</i>-butylpyrrolidinium nonafluoro-1-butanesulfonate (p_1,4NfO) has the lowest melting point of the family, at 94 °C. Electrochemical analysis of p_1,4 NfO in the liquid state shows an electrochemical window of ~6 V. All compounds exhibit one or more solid–solid transitions at sub-ambient temperatures, indicating the existence of plastic crystal phases.<br />