Epoxy Adhesives with Reversible Hardeners: Controllable Thermal Debonding in Bulk and at Interfaces.

On-demand adhesive dismantling has the potential to improve multi-material product recycling, but its implementation has been hampered by a critical trade-off between strong bonding and easy debonding. As a result, the temperature range in which these temporary adhesives can be used is relatively limited. Here, we report a new class of dynamic epoxy resins that significantly extends this upper temperature limit and still achieves fast debonding. Specifically, two types of dynamic polyamidoamine curing agents for epoxy hardening were developed, being polysuccinamides (PSA) and polyglutaramides (PGA). As the dynamic debonding/rebonding process of PSA and especially PGA linkages is more thermally demanding and at the same time more thermally robust than previously reported dynamic covalent systems, the resulting materials can be triggered at high temperatures, and at the same time remain bonded over a wide temperature range. The versatility of the PSA and PGA dynamic adhesive curing system was demonstrated in classical bulk adhesive formulations, as well as in dynamic covalent linking to a PSA- or PGA-functionalised surface. As a result, an attractive drop-in strategy was achieved for producing debondable and rebondable epoxy adhesives, with high complementarity to existing adhesive resin technologies and applicable in an industrially relevant temperature window. This article is protected by copyright. All rights reserved.