Bio-based recyclable polydithioacetal covalent adaptable networks with activation-temperature-tunable shape memory properties

The extensive development of polymer materials from fossil resources poses serious environmental challenges. Therefore, developing recyclable functional materials from biomass is crucial. Here, we confirmed the reversible exchange ability of dithioacetal bonds through a model compound exchange reaction. Crosslinked polydithioacetal (PDTA) was prepared via solvent-free polycondensation of biomass benzaldehyde and tetra-thiol monomers at room temperature. Self-healing and multi-mode recycling, including mechanical reprocessing, chemical recycling, and back-to-monomer recycling, were achieved under mild conditions with no mechanical performance reduction. The solid-state plasticity due to the dynamic nature of polydithioacetal endowed PDTA with reconfigurable shape memory capability, which ensured the flexible application of PDTA by allowing reconfiguration of its permanent shape and recovery route direction. Moreover, the activation temperature for shape memory can be facilely tuned by adjusting the crosslinking densities of PDTA to meet medical application needs. With its facile tunability, great hydrolytic resistance and biocompatibility, PDTA exhibited outstanding performance in a vascular stent demonstration experiment, in which a shrunken stent made of body temperature-responsive PDTA expanded and provided support within the vessel, showing the promise of PDTA as an environmentally and biologically friendly material for the implanted biomedical stent.