“Polymer to polymer” recycling and body-temperature triggered shape memory of a carvone-based epoxy thermoset system achieved using a thiol-Michael covalent adaptable network

Abstract

Environmental economics is intensifying the necessity for the advancement of recycling technologies to address the increasing volume of discarded thermoset polymers. Covalent adaptable networks (CANs) provide a new strategy for the recycling and functionalization of thermosetting resins. Herein, a carvone-based CAN is developed, in which thermally driven depolymerization of mechanically robust polymer networks is achieved by dynamic thiol-Michael bonds. The original cross-linking network can be retained through simple drying and hot-pressing steps without purifying degradation products. The reversibility of the thiol-Michael group is demonstrated and the CAN exhibits shape memory behaviors triggered by human body temperature. We propose a micro-robotic injection model with good mechanical strength and fast response speed for complex 1D to 3D shape morphing in aqueous media at 37 °C. Our findings present a high-quality strategy to realize recycling and functionalization of bio-based thermoset resins and expand the toolbox for the preparation of bio-based CANs with thermo-responsive behavior.