Enabling the Reprocessability and Debonding of Epoxy Thermosets Using Dynamic Poly(β-Amino Amide) Curing Agents

Abstract

Epoxy resins, by showing outstanding performances, stand out as the most applied materials in thermoset products. However, their excellent properties, associated with covalently cross-linked structures, come at the expense of recyclability, thus posing environmental and regulatory challenges. Herein, starting from the recently explored reversibility of robust poly(β-amino amide)s, dynamic curing agents are synthesized in a one-pot procedure for their use in the preparation of epoxy-derived dynamic networks. The obtained materials retain desirable properties while being fully (re)processable, with high temperature-dependent viscoelasticity (activation energy (E_a) of ≈230 to 270 kJ mol⁻¹). Moreover, this new generation of epoxy materials shows excellent resistance to hydrolysis and creep at elevated temperatures (up to 120 °C). As an entry point to further applications, the reversible curing agents are implemented in adhesive formulations, showcasing lap shear strengths that are comparable to commercial hardeners (up to 9 MPa). The β-amino amide groups provide the obtained adhesives with the additional functionality of heat-triggered deconstruction at elevated temperatures (130 to 150 °C), and re-bonding capacity with up to 80% recovery in lap-shear strength. To encourage industrial adoption, a cost-effective, drop-in synthesis protocol is developed using only bulk chemicals, hence facilitating practical implementation.