A Chemically Recyclable 1,3,5-Triazine-Based Epoxy Thermoset Enabled by Nucleophilic Aromatic Substitution Reaction.

Developing recyclable thermosets without sacrificing structural integrity remains a significant hurdle in polymer circularity. In this study, we present a high-performance, chemically recyclable epoxy thermoset based on 1,3,5-triazine, demonstrating significant advancements in material recyclability and application potential. Utilizing liquid precursors, that is a trifunctional epoxy monomer (TOMTA) and a strategically selected secondary aromatic diamine hardener (MBMA), a cross-linked network with a well-defined architecture was produced under bulk conditions. The resulting thermoset exhibited exceptional thermal and mechanical properties as evidenced by a high glass transition temperature (Tg = 105°C), thermal stability (Td5% = 256°C), a Young's modulus of 3.0 GPa, and a tensile strength of 96 MPa, placing the material in the same performance range of conventional epoxy resins. Driven by an optimized binary K2CO3/TBD catalytic system in ethanol, the network underwent depolymerization enabled by a nucleophilic aromatic substitution reaction (SNAr), yielding the well-defined building blocks TETA and the tetraol BDHPPM in 70% and 65%, respectively, via straightforward liquid-liquid extraction. Re-crosslinking these recovered building blocks regenerated the network, preserving nearly identical properties across multiple recycling cycles. The system was further applied as a debondable coating for glass. This 1,3,5-triazine-based network utilizing SNAr chemistry provides a robust route to high-performance, recyclable epoxy thermosets.