Light-based additive manufacturing techniques have rapidly transformed polymer manufacturing capabilities, due to the simplicity of their hardware, high spatial resolutions, and reasonable printing speeds. However, the mechanical properties accessible with compatible photopolymerization chemistries remain limited compared to traditional methods, thus limiting its applicability. Furthermore, there is a demonstrated need for strategies to introduce reprocessing and recycling capabilities within additive manufacturing materials to reduce the environmental impact of produced parts. In this work, we develop a thiol-ene system containing dynamic covalent bonds that affords both optimized mechanical performance as well as molecular means for polymer degradation and repolymerization. We show that through judicious selection of monomer components, we can produce semi-crystalline networks with thermoplastic-like toughness. Additionally, by incorporating thioester groups within these networks, these materials can be degraded using free thiols into functional oligomers that can be repolymerized into new networks. Significantly, these oligomer feedstocks can be used to reclaim pristine network properties or used to access other desired materials such as elastomers and glassy materials. We demonstrate that this system is compatible with commercial SLA printers, and explore how printing parameters affect mechanical properties compared to bulk polymerized materials. Finally, we show that an additional benefit of incorporating crystallinity and dynamic bonds within a single networks facilitates capabilities such as shape memory and self-healing to prolong the lifespan and utility of printed parts.

Photopolymerizable and mechanically-diverse recyclable polymers: Fundamentals and applications to additive manufacturing

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ACS Spring 2023

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