A new way to synthesize epoxy networks was reported in this work using phosphonium based ionic liquids combined with phosphinate, carboxylate, and phosphate counter anions. The influence of the chemical nature of the anions was investigated on the polymerization kinetics of epoxy systems as well as the thermal and mechanical properties of epoxy IL networks. In all cases, ILs displayed a high reactivity toward epoxy prepolymer and led to the formation of poly epoxy networks with high epoxy group conversion, i.e., up to 90%. In addition, epoxy IL networks have high hydrophobicity and an excellent thermal stability (above 350 degrees C) under N-2 with the glass transition temperatures (T-g) ranging from 90 to 140 degrees C depending on the chemical structure of ILs. For the first time, the mechanical properties of epoxy IL networks were also evaluated in terms of flexural properties and fracture toughness (K-Ic).