Thermal Stability of Protic Ionic Liquids

Area of Science:

• Chemistry
• Materials Science

Background:

• Protic ionic liquids (ILs) are versatile solvents with growing applications.
• Limited data exists on the long-term thermal degradation of protic ILs at elevated temperatures.

Purpose of the Study:

• To investigate the thermal stability of six common protic ionic liquids.
• To evaluate the impact of prolonged heating (1 hour vs. 1 week) at 60°C on IL properties under sealed and open conditions.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal phase transitions.
• Proton nuclear magnetic resonance (¹H NMR) spectroscopy for molecular structure.
• Monitoring changes in water content, pH, and mass.

Main Results:

• Sealed heating resulted in minor shifts in water content and pH, with no significant changes in mass, thermal transitions, or molecular structure.
• Open heating for 1 hour showed no significant changes.
• Open heating for 1 week caused significant degradation and property changes in the protic ILs.

Conclusions:

• Protic ionic liquids exhibit good thermal stability under sealed conditions at 60°C.
• Exposure to ambient atmosphere during prolonged heating accelerates the degradation of protic ionic liquids.
• Understanding these degradation pathways is crucial for optimizing IL applications and storage.