Direct Monomer Recovery from Ring-Closing Depolymerization of Thermosets

Recovering monomers from the depolymerization of thermosets presents a significant challenge, which becomes even more daunting if one sets the goal of doing it directly, i.e., without complex chemical separation steps. To this end, we have synthesized a new type of polycarbonate thermoset by first copolymerizing alkyl cyclic carbonates (<b>ACC</b>s) with small amounts of allyloxy cyclic carbonates (<b>AoCC</b>s), followed by cross-linking the resulting allyloxy polycarbonate with excess tetrathiol compounds under UV irradiation. These cross-linked polycarbonates demonstrate enhanced thermal and mechanical properties compared to their linear analogues, while maintaining the linear polymers' capacity for ring-closing depolymerization. The depolymerization process enables the direct recovery of <b>ACC</b> and its dimer, bypassing complex chemical separation steps that are commonly employed in the recycling of conventional chemically recyclable thermosets. The yields range from 74.7% to 91.7% depending on the ratios of <b>AoCC</b> to <b>ACC</b> in the thermosets. Furthermore, the recovered compounds can be repolymerized with <b>AoCC</b>s leading to polycarbonate of the same quality to the initially synthesized one.