In a sustainable circular economy, polymers capable of chemical recycling to monomers are highly desirable. We report an efficient monomer-polymer recycling of polydithioacetal (PDTA). Pristine PDTAs were readily synthesized from 3,4,5-trimethoxybenzaldehyde and alkyl dithiols. They then exhibited depolymerizability via ring-closing depolymerization into macrocycles, followed by entropy-driven ring-opening polymerization (ED-ROP) to reform the virgin polymers. High conversions were obtained for both the forward and reverse reactions. Once crosslinked, the network exhibited thermal reprocessability enabled by acid-catalyzed dithioacetal exchange. The network retained the recyclability into macrocyclic monomers in solvent which can repolymerize to regenerate the crosslinked network. These results demonstrated PDTA as a new molecular platform for the design of recyclable polymers and the advantages of ED-ROP for which polymerization is favored at higher temperatures.
Polydithioacetals , a new class of chemically recyclable thermoplastic and thermoset polymers, depolymerize to give a mixture of homologous macrocyclic monomers. Ying Yang and co‐workers demonstrate in their Research Article (e202303039) that these monomers regenerate the virgin polymer via entropy‐driven ring‐opening polymerization with high conversions at ambient temperatures.
Polymers capable of chemical recycling to monomers are highly desirable to produce sustainable materials with a circular economy. We here report a highly efficient ring-chain recycling of polydithioacetal (PDTA) via ring-closing depolymerization (RCD) and entropy-driven ring-opening polymerization (ED-ROP). Pristine PDTAs can be conveniently synthesized via a one-step reaction using 3,4,5-trimethoxybenzaldehyde and α,ω-alkyl dithiols with an acid catalyst. The resulting PDTAs undergo acid-catalyzed RCD with refluxing toluene to yield a mixture of macrocycles of various sizes with conversions of 75-95%. ED-ROP of these macrocyclic monomer mixtures in solution at room temperature affords virgin PDTAs, reaching high conversions of 80-95% within 2 h. Owing to the stability of dithioacetals, PDTAs are far more stable than the acetal counterparts, resisting hydrolysis under both acidic and basic conditions. With a floor temperature below 0 °C, depolymerization is not a concern in the bulk state even in the presence of residual catalysts as polymerization is favored at higher temperatures for ED-ROP. Once crosslinked, the network behaves as a vitrimer enabled by temperature-activated interchain exchange of dithioacetals in the bulk state. The vitrimer depolymerizes into macrocyclic monomers in solvent which can repolymerize to regenerate the vitrimer.
Polymers capable of chemical recycling to monomers are highly desirable to produce sustainable materials with a circular economy. We here report a highly efficient ring-chain recycling of linear polydithioacetal (PDTA) via ring-closing depolymerization (RCD) and entropy-driven ring-opening polymerization (ED-ROP). Furthermore, once crosslinked, the network behaves as a vitrimer enabled by temperature-activated interchain exchange of dithioacetals in the bulk state. The vitrimer depolymerizes into macrocyclic monomers in solvent which can repolymerize to regenerate the vitrimer. Pristine linear PDTAs can be conveniently synthesized via a one-step reaction using 3,4,5-trimethoxybenzaldehyde and α,ω-alkyl dithiols with an acid catalyst. The resulting PDTAs undergo acid-catalyzed RCD with refluxing toluene to yield a mixture of macrocycles of various sizes with conversions of 75-95%. ED-ROP of these macrocyclic monomer mixtures in solution at room temperature affords virgin PDTAs, reaching high conversions of 80-95% within 2 h. Owing to the stability of dithioacetals, PDTAs are far more stable than the acetal counterparts, resisting hydrolysis under both acidic and basic conditions. With a floor temperature below 0 °C, depolymerization is not a concern in the bulk state even in the presence of residual catalysts as polymerization is favored at higher temperatures for ED-ROP.
Polydithioacetals , a new class of chemically recyclable thermoplastic and thermoset polymers, depolymerize to give a mixture of homologous macrocyclic monomers. Ying Yang and co‐workers demonstrate in their Research Article (e202303039) that these monomers regenerate the virgin polymer via entropy‐driven ring‐opening polymerization with high conversions at ambient temperatures.
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