Reprocessable Covalent Adaptable Networks Enabled by Transamidation and Imine Metathesis Exchanges

Abstract

Here, we report the preparation of a series of dynamic covalent poly(amide-imine) materials synthesized from a biobased triester monomer: methyl tricarballylate (TM), commercial di- and triamines (tris(2-aminoethyl)amine, Jeffamine D230, and hexamethylene diamine), and a synthesized imine-containing diamine (IDA). These high-T_g materials (>79 °C) feature dynamic amide and imine groups that contribute independently to material dynamicity while exhibiting a synergistic effect through transimination reactions promoted by primary amines released during amide dissociation. The coexistence of these two dynamic moieties enhances stress relaxation; however, the relaxation kinetics result from a delicate balance between dynamic chemistry rates and network architecture. We demonstrated that modulating the proportion of the imine-containing monomer, the flow behavior of the prepared materials can be controlled, shifting from a purely dissociative to a mainly associative viscous profile. This acquires great technological relevance considering the critical importance of material flowability in several manufacturing processes and industrial applications. Adhesive testing revealed a strong correlation between adhesive strength and high-temperature viscosity, along with facile debondability under extremely low loads. These findings demonstrate that amide exchange and imine metathesis/transimination are promising dynamic partners for unlocking rheological properties unattainable with conventional thermosets, thereby expanding applications in high-performance fields.