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Anomalous electrical conductivity behavior at elevated pressure in the protic ionic liquid procainamide
Z Wojnarowska1, C M Roland, A Swiety-Pospiech
1Institute of Physics, Silesian University, ul. Uniwersytecka 4, 40-007 Katowice, Poland.
Physical Review Letters
|February 7, 2012
Summary
Hydrostatic pressure causes anomalous conductivity relaxation in procainamide hydrochloride near its glass transition. This study reveals a decoupling of ion migration from structural relaxation in glassy ionic liquids.
Area of Science:
- Materials Science
- Physical Chemistry
- Condensed Matter Physics
Background:
- Protic ionic liquids (PILs) are promising electrolytes with unique properties.
- Understanding their behavior under pressure is crucial for applications.
- Procainamide hydrochloride is a relevant pharmaceutical compound with ionic liquid characteristics.
Purpose of the Study:
- To investigate the influence of hydrostatic pressure on conductivity relaxation in supercooled procainamide hydrochloride.
- To explore the relationship between electrical conductivity and structural relaxation under varying pressure conditions.
- To identify anomalous behaviors near the glass transition temperature (Tg).
Main Methods:
- Broadband dielectric spectroscopy was employed to measure conductivity relaxation time (τσ).
- Experiments were conducted under varying hydrostatic pressure conditions.
- Isothermal densification was used to probe the system's response.
Main Results:
- Anomalous pressure dependence of τσ was observed near Tg.
- Abrupt changes in activation volume indicated unique pressure effects.
- Decoupling of electrical conductivity from structural relaxation was identified.
Conclusions:
- The study provides the first evidence of ion migration decoupling from structural relaxation in a glassy conductor via isothermal densification.
- Free ions maintain mobility in the glassy state, albeit with diminished sensitivity to thermodynamic changes.
- Observed anomalies highlight the complex interplay between pressure, ion dynamics, and structural rearrangements in PILs.
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