Metal Ionic Liquids (MILs) as Promising Catalytic Curing Agents of Epoxy Prepolymer for the Design of High‐Performance Networks

ABSTRACT A new promising alternative to substitute conventional hardeners of epoxy prepolymers such as amine and anhydride is reported in this work. Here, imidazolium metal‐based ionic liquids (MILs) containing (CoCl 4 ) 2 − , (MnCl 4 ) 2 − and (ZnCl 4 ) 2 − anions are used for the first time as catalytic curing agents of a tetrafunctional epoxy prepolymer denoted N,N,N’,N’‐tetraglycidyl‐4,4’‐diaminodiphenyl methane (TGDDM) used in advanced composite materials. These MILs, easily synthesizable from inexpensive metallic salts, are proven to be effective catalytic curing agents for the polymerization of tetrafunctional epoxy monomers. In fact, their use leads to a high epoxy group conversion for very small ILs amounts (3 and 5 phr, i.e. parts by weight per 100 parts by weight of epoxy resin) and they act as latent hardeners, allowing to control the polymerization. Thus, we have evaluated the influence of the chemical nature of the counter anions as well as the MIL content (3‐5‐10 phr) on polymerization kinetics and physical properties of the crosslinked epoxy materials. The networks exhibit excellent thermal stability (> 350°C), high glass transition temperature (180°C) and good thermomechanical properties, making them good candidates for high‐performance composite materials. Moreover, others key features for epoxy networks such as mechanical performances and water sensibility were determined, and the morphologies of the networks highlighting the structuration of MILs were investigated by SEM micrographs.