Tunable reinforcement of epoxy-silica nanocomposites with ionic liquids

Imidazolium ionic liquids (ILs) have the capacity to exert multiple functions as additives for the formation of epoxy-silica nanocomposites, via the simultaneous sol–gel process and epoxy network build-up. This study addresses the effect of ILs on the reinforcement of tensile properties in rubbery epoxy-silica nanocomposites, allowing property tailoring. The use of ILs together with the coupling agent 3-glycidyloxypropyltrimethoxysilane (GTMS) created a synergic action between physical and chemical interfacial bonding, enabling an increase in toughness without a considerable loss of stiffness. The best tensile property balance was obtained with IL 1-triethylene glycol monomethyl ether-3-methylimidazolium methanesulfonate and GTMS. The rubbery nanocomposite produced was remarkably both stiffer and tougher than the unmodified epoxy-silica system, displaying ca. 6 times higher modulus and tensile strength as well as more than 10 times higher energy to break.