Evaluating thermal decomposition of ionic liquids and deep eutectic solvents for reliable and consistent thermal analysis: Issues, factors, classifications and suggestions

Abstract

Ionic liquids (ILs) and deep eutectic solvents (DESs) are both deemed as green solvents of 21st century with no thermal decomposition and thus have attracted much attention in academic research and industrial application. No or negligible thermal decomposition is the basis for the praise of green solvents and the premise for the wide application of ILs and DESs. Nevertheless, evaluation of thermal decomposition with high accuracy and high consistency is the key for the analysis of thermal stability of ILs and DESs, which is severely ignored and overlook. Many reviews focus on the strategies to reduce thermal decomposition, factors affecting decomposition, kinetics and mechanism of thermal decomposition; however, there is no review summarizing the accurate and reliable evaluation of thermal decomposition of ILs and DESs to the best of our knowledge. Here, we summarize the factors affecting the evaluation of thermal stability of ILs and DESs and propose the accurate and reliable standards to evaluate the thermal stability of ILs and DESs. The purpose of this review is to clarify the fundamentals of thermal decomposition evaluation for the reliable, consistent and accurate thermal analysis.