Chemically recyclable and reprogrammable epoxy thermosets derived from renewable resources†

Abstract

Epoxy thermosets constitute a significant portion of high-performance plastics due to their excellent thermal and mechanical properties, making them suitable for a wide range of applications. However, traditional epoxy networks are produced from a petroleum-based, reprotoxic and endocrine-disruptor DGEBA and face significant limitations in chemical recycling. Current recycling methods for epoxy systems rely on harsh and non-green conditions, often resulting in a mixture of small molecules and oligomers that are tedious to isolate or repurpose. Consequently, it is crucial to develop bio-based monomers with functional groups that enable the synthesis of fully recyclable polymers. For this purpose, herein, we have employed a bio-based, liquid monomer C2 derived from vanillin, containing aldehyde, acetal, and oxirane-ring functionalities, which was polymerized under solvent-free, green conditions with bio-derived diamines, resulting in an array of doubly cleavable epoxy thermosets with diverse thermal and mechanical properties. These networks combine the desirable properties of traditional epoxy systems with intrinsic mildly cleavable nature. Remarkably, these thermosets can be fully depolymerized into reusable vanillin and well-defined polyols, or they can be recycled and reprogrammed through a transimination pathway. This innovative approach, combining controlled depolymerization, closed-loop recycling and reprogramming, offers significant potential for sustainable polymer management.