Do Ionic Liquids Slow Down in Stages?

High impact recent articles have reported on the existence of a liquid-liquid (L-L) phase transition as a function of both pressure and temperature in ionic liquids (ILs) containing the popular trihexyltetradecylphosphonium cation (P (+)(666,14)), sometimes referred to as the universal liquifier. The work presented here reports on the structural-dynamic pathway from liquid to glass of the most well-studied IL comprising the P (+)(666,14 )cation. We present experimental and computational evidence that, on cooling, the path from the room-temperature liquid to the glass state is one of separate structural-dynamic changes. The first stage involves the slowdown of the charge network, while the apolar subcomponent is fully mobile. A second, separate stage entails the slowdown of the apolar domain. Whereas it is possible that these processes may be related to the liquid-liquid and glass transitions, more research is needed to establish this conclusively.

Automated summary

This article reports on the structural-dynamic pathway from liquid to glass in ionic liquids containing a specific cation. Experimental and computational evidence suggests that the transition from liquid to glass occurs in separate stages.