Biobased Thermosets with an All‐Hydrocarbon Backbone: A Platform Enabling Fully Multicomponent Closed‐Loop Chemical Recyclability

Conventional petroleum‐based thermosetting resins, characterized by their three‐dimensional crosslinked networks, offer outstanding performance yet are plagued by challenges related to incomplete degradation and low recycling efficiency. Current recovery methods relying on degradable heteroatom bonds are further constrained by poor environmental resistance and the difficulty of recovering crosslinking components. To address these limitations, this study proposes a novel design strategy for biomass‐derived thermosetting resins based on low ring‐strain building blocks. Using alcohol derivatives from biomass (including coconut oil, straw, and corn starch) as raw materials, we synthesized a monofunctional cyclooctene monomer and multifunctional crosslinkers, subsequently constructing oil‐based thermosetting resins with all‐carbon backbones via ring‐opening metathesis polymerization (ROMP). The resulting biobased resins exhibit excellent thermal stability ( T d,5% > 340°C) and precisely tunable glass transition temperatures. The low ring‐strain imparted by the ketal‐modified building units enables controlled depolymerization of the resin via olefin metathesis under mild conditions (50°C). This process achieves the simultaneous recovery of both the pristine monomer and crosslinkers, with a maximum total recovery rate of 95.6%, thus establishing a fully reactant closed‐loop chemical recycling system. This work provides a new strategy for their green synthesis and offering robust support for the low‐carbon, sustainable development of polymeric materials.