Catalyst-Free Dynamic Crosslinking of Polydicyclopentadiene via Thiol–Ene/Imine Chemistry

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Abstract The permanently crosslinked nature of thermosets fundamentally prevents recycling, creating persistent waste and environmental challenges. Among high-performance thermosets, polydicyclopentadiene (pDCPD) is widely used in transportation and infrastructure, yet most end-of-life material is landfilled or incinerated because its irreversibly crosslinked network resists conventional reprocessing. Here, pDCPD, a polynorbornene-based thermoset valued for its mechanical strength, chemical resistance, and compatibility with additive manufacturing, is upcycled into a dynamic covalent network (DCN) by introducing imine linkages. A two-step thiol–ene/imine sequence converts the permanent network into a (re)processable vitrimer-like material. Our dynamic pDCPD preserves high mechanical performance, exhibiting more than a 7-fold higher elastic modulus retention after recycling compared to its unmodified counterpart. Reversible imine chemistry also imparts intrinsic healing capability, reducing the incision width by ∼92% under simple, free-standing thermal treatment. This strategy establishes a practical route to convert pDCPD waste into DCNs, advancing sustainable thermoset design.

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