Ionic liquids based on trihexyl(tetradecyl)phosphonium combined with dicyanamide counteranion were used for the first time as functional additives to achieve epoxy networked polymeric materials which display a structuration at nanoscale (20–30 nm) with dramatic mechanical properties and a higher thermal stability (>400 °C). In fact, the curing process was studied by FTIR, DSC highlighting an increase of the conversion epoxide groups in function of the IL amount (5–30 phr) and the morphology has been revealed by transmission electronic microscopy (TEM) and atomic force microscopy (AFM).