(410f) High Pressure Studies As a Key for Understanding the Ion Dynamics of Polymerized Ionic Liquids

Ion transport plays an important role in biological systems as well as in a variety of electrochemical devices including fuel cells and batteries. Despite a number of reports addressing this issue there is still lack of satisfactory description of ion dynamics in condensed materials. Herein, we studied the ion dynamics of a 1,2,3-triazolium-based poly(ionic liquid) (PIL) at both ambient and elevated pressure using broadband dielectric spectroscopy. We show that the isothermal and isobaric conductivity measurements analyzed in the 3D plane give a unique possibility to estimate the thermodynamic (isothermal compressibility and thermal expansion coefficient) properties for PILs having a charge transport fully controlled by viscosity. This result, providing a direct connection between thermodynamic and dynamic properties of PILs, is of significant importance for both material scientists and practical applications. We also found that fast mobility manifested by a secondary β process promotes segmental dynamics and thereby increases ionic conductivity making the studied material a first coupled PIL of superionic properties. The molecular mechanism underlying such a β process has been identified as Johari-Goldstein relaxation giving experimental proof that fast secondary relaxations of intermolecular origin exist also in PILs and thereby reveal a universal character.