Self-catalysed coupling between Brønsted-acidic imidazolium salts and epoxy-based materials: a theoretical/experimental study

Herein we present a comprehensive study on the role of Bronsted-acidic imidazolium ionic liquids (ILs) and imidazolium salts promoting the reaction between carboxyl and epoxide groups in a controlled manner at solvent-free and mild conditions. ILs were evaluated towards their ability to self-catalyze reactions between carboxyl groups and epoxy rings. Thus, an epoxy model reactant denoted phenyl glycidyl ether (PGE) was reacted with different ILs and the reaction kinetics was followed by time-dependent FTIR spectroscopy. The resulting products were characterized by 1HNMR and MALDI-TOF, which also allowed a comprehensive investigation of the reaction mechanism by following the reaction intermediates formation. The detected intermediates were then evaluated by density functional theory (DFT) simulations in order to calculate their energy profiles, revealing the preferred mechanism pathways. These mono, bi and tetra-functionalized ILs (with carboxyl groups) acted as all-in-one reaction systems for materials s...