Multi-Generational Frontal Curing and Chemical Recycling of Polydicyclopentadiene Thermosets

Polydicyclopentadiene (pDCPD) is a high-performance thermoset with lightweight and exceptional thermomechanical properties. However, its traditional thermal curing process is energy-intensive and lacks chemical recyclability. Frontal Ring-Opening Metathesis Polymerization (FROMP) is an energy-efficient curing process and allows additive manufacturing of pDCPD. 2,3-Dihydrofuran (DHF) has been shown as an effective comonomer to allow the deconstruction of pDCPD thermosets when incorporated at a small fraction in pDCPD. Herein, a simple strategy for chemical recycling of pDCPD thermosets is reported, and maintaining FROMP characteristics and thermomechanical properties of the thermosets over five life cycles. Norbornadiene (NBD) is a key additive in resins containing recycled pDCPD to enhance polymerization kinetics and sustain FROMP characteristics. A one-pot strategy is also developed to deconstruct pDCPD thermosets and simultaneously functionalize the chain ends with norbornenes for reincorporating deconstructed oligomers back to the next generation thermoset. Using these strategies, five generations of recycling pDCPD thermosets with invariable thermomechanical properties are demonstrated. This work highlights a scalable and energy-efficient process to produce chemically recyclable pDCPD thermosets, significantly improving the circularity of this class of high-performance thermosets.