A series of amide-functionalized ionic liquids (ILs), e.g., 1-R-3-(2-amino-2-oxoethyl)-imidazolium (R = −vinyl, −methyl–butyl) cations combined with Cl–, N­(CN)­2–, or NTf2 – anions, were synthesized and fully characterized as curing agent for diglycidyl-4,5-epoxy-cyclohexane-1,2-dicarboxylate (TDE-85). Studies of curing behaviors showed that ILs with N­(CN)2 – anions exhibit moderate curing conditions. As to thermosets of TDE-85 cured by these curing agents, their tensile strength (95.1–111.7 MPa) and elongation at break (2.69 to 4.20%) are significantly improved compared with the traditional curing systems of DDS/TDE-85 (DDS, 4,4′-diamino diphenyl sulphone). These thermosets also exhibit good thermal mechanical properties with the glass transition temperature (T g) > 200 °C and thermal degradation temperature (T d) > 300 °C. The possible mechanisms of curing reactions were analyzed by using IR, and results indicated that curing reactions of TDE-85 with amide-functionalized ionic liquids may include three steps, −NH2 groups reacted with oxirane at lower temperatures, and then the anions further participated in the reaction to strengthen the cross-linking networks. This study provides informative guidelines for designing new curing agents.

As epoxy resin curing agents, ionic liquids can help improve mechanical properties, flame retardancy, and wear and tear self-healing and extend the pot life of epoxy compositions. The functional design of ionic-liquid curing agents may significantly improve the overall performance of epoxy resins. In this paper, a series of dual-functionalized ionic liquids, e.g., 1-(3-amino-3-oxopropyl)-3-propynyl-imidazolium, 1-(3-amino-3-oxopropyl)-3-(2-amino-2-oxoethyl)-imidazolium, and 1-allyl-3-(2-amino-2-oxoethyl)-imidazolium combined with dicyanamide (N­(CN)2 –) or bis­(trifluoromethylsulfonyl)­imide (NTf2 –) anions, were synthesized and characterized as curing agents for diglycidyl-4,5-epoxy-cyclohexane-1,2-dicarboxylate (TDE-85). The results showed that the obtained bifunctional ionic liquids can be used as a medium or high-temperature curing agents for TDE-85 with the curing temperature range of 130–208 °C and the best mass ratio range of 15:100–40:100. Thermosets obtained from the bifunctional ionic liquid and TDE-85 curing system exhibit better heat resistance with the glass transition temperature of 187–212 °C and the decomposition temperature at 10% weight loss of 282–357 °C. The curing reaction mechanism of the 1-(3-amino-3-oxopropyl)-3-(2-amino-2-oxoethyl)-imidazolium NTf2 –/TDE-85 system mainly has three processes.

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