Sulfobetaine ionic liquid crystals based on strong acids: phase behavior and electrochemistry

Abstract

A group of new zwitterion based ionic liquid crystals (ILCs) have been synthesized. Depending on the counter anion (mesylate or hydrogen sulfate) the phase behavior of the resulting ILCs is quite different. Mesylate based ILCs show complex phase behavior with multiple phases depending on the alkyl chain length. In contrast, hydrogen sulfate based systems always exhibit Col_r phases irrespective of the alkyl chain length. The latter show much larger ILC mesophase windows and are thermally stable up to ca. 200 °C. All ILCs show reasonable ionic conductivities of up to 10⁻⁴ S cm⁻¹ at elevated temperatures, making these ILCs candidates for intermediate temperature ionic conductors.