Degradable Polydithioacetals with Adjustable Mechanical Properties and Insights into Entropy-Driven Ring-Opening Polymerization

Abstract

The environmental challenges posed by the persistence of synthetic polymers after disposal underscore the need for sustainable alternatives. Polydithioacetals have shown promise as candidates for ring–chain recycling through ring-closing depolymerization, generating a mixture of macrocycles and entropy-driven ring-opening polymerization back to the polymers. A major limitation of previously synthesized polydithioacetals has been their poor thermomechanical properties. In this study, we demonstrated that incorporating varying ratios of alkyl and aryl dithiol monomers into the linear polydithioacetal backbone significantly enhanced the mechanical properties compared with the homopolymers. The modified copolymers exhibited glass transition temperatures ranging from −2 to 90 °C and improved mechanical properties, including an increase in tensile strain up to 387%, making them comparable to some commodity polymers. These polymers are thermally stable up to 297 °C. High molecular weight polymers were achieved by introducing additional benzaldehyde and adjusting the ratios of monomer, catalyst, and initiator, providing insights into the ring-opening polymerization mechanism of macrocyclic dithioacetals.