Comparing Triaminononane and TREN as Trifunctional Amine Cross-Linkers in Covalent Adaptable Networks

Primary amines are of utmost importance for the design of various polymeric materials, because of their reactivity, low cost and widespread availability. This is demonstrated by the numerous cross-linking strategies of thermosets that rely on the reaction of multifunctional amines with for example epoxides, esters or aldehydes. Tris-(2-aminoethyl)-amine (TREN) has long remained the only large-scale available, low mass trifunctional primary amine. Despite its known toxicity, significant vapor pressure and several drawbacks related to its tertiary amine functionality, including oxidation-induced coloration, reduced thermal stability and increased reactivity, TREN helped to shape the field of covalent adaptable networks (CANs). On the other hand, we anticipated that triaminononane (TAN) as an alternative low-viscosity trifunctional primary amine would not face the same difficulties because of its fully aliphatic structure. Therefore, in this study we compare the performance of TREN and TAN by synthesizing CANs using two well-established dynamic chemistries, i.e. amide-imide and vinylogous urethane exchange. Through an in-depth study of their thermomechanical properties, the influence of both cross-linkers was examined, providing valuable insights for researchers in selecting the most suitable cross-linker.