Relationship between glass-transition pressure of pressurized homologous imidazolium-based ionic liquids and internal pressure from activation volume measurements

The influence of the interactions between ions on the glass properties of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids is investigated by measuring the activation volume nV at different molecular volumes by varying the length of the cation alkyl chain. The activation volume is determined at room temperature from impedance spectroscopy measurements for increasing pressures maintained below the glass-transition pressure Pg. We show that the energy EnV required to increase the volume by the amount nV against the internal pressure of the ionic liquid is well correlated with Pg, where an almost linear increase in Pg is observed with increasing EnV. These results highlight the impact of intermolecular interactions on the glass properties, and suggest that the energy associated to nV could be related to the energy landscape in which the ions diffuse.

Automated summary

This study investigates the influence of intermolecular interactions on the glass properties of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids. It is found that the energy required to increase the volume is well correlated with the glass-transition pressure, suggesting a connection between the energy landscape and ion diffusion.