Amide-Functionalized Ionic Liquids As Curing Agents for Epoxy Resin: Preparation, Characterization, and Curing Behaviors with TDE-85

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 diglycidy1-4,5-epoxy-cyclohexane-1,2-dicarboxylate (TDE-85). Studies of curing behaviors showed that lLs 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 degrees C and thermal degradation temperature (T-d) > 300 degrees 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.