Vat Photopolymerization Additive Manufacturing of Tough, Fully Recyclable Thermosets

Abstract

To advance the capabilities of additive manufacturing, novel resin formulations are needed that produce high-fidelity parts with desired mechanical properties that are also amenable to recycling. In this work, a thiol–ene-based system incorporating semicrystallinity and dynamic thioester bonds within polymer networks is presented. It is shown that these materials have ultimate toughness values >16 MJ cm^–3, comparable to high-performance literature precedents. Significantly, the treatment of these networks with excess thiols facilitates thiol–thioester exchange that degrades polymerized networks into functional oligomers. These oligomers are shown to be amenable to repolymerization into constructs with varying thermomechanical properties, including elastomeric networks that recover their shape fully from >100% strain. Using a commercial stereolithographic printer, these resin formulations are printed into functional objects including both stiff (E ～ 10–100 MPa) and soft (E ～ 1–10 MPa) lattice structures. Finally, it is shown that the incorporation of both dynamic chemistry and crystallinity further enables advancement in the properties and characteristics of printed parts, including attributes such as self-healing and shape-memory.