Depolymerizable Elastomeric Polyolefin Thermosets with Great Extensibility

The development of high-performance rubber materials has been a long-standing pursuit; currently, this has to go hand-in-hand with the design of polymers that are in some way recyclable. In this work, we report a class of thermosetting polyolefin elastomers synthesized via ring-opening metathesis polymerization of cycloheptene cross-linked with dicyclopentadiene. These cross-linked thermosets exhibit markedly enhanced chemical resistance, mechanical robustness, thermomechanical stability, and elasticity compared to those of their linear analogue. Notably, they demonstrate extraordinary extensibility, with strain at break exceeding 1700%, attributed to strain-induced crystallization confirmed by small- and wide-angle X-ray scattering analyses. Moreover, the elastomers are depolymerizable in the presence of Grubbs Catalyst second Generation, enabling recovery of cycloheptene in good yields of 77%-92%. Lastly, we show that the (thermo)-mechanical properties of the materials could be further enhanced through the incorporation of activated charcoal, and the resulting composites still retain a certain level of depolymerizability, affording cycloheptene in a yield of 60%.