A Versatile Platform for Recyclable Polyesters: Alternating Copolymerization of Aldehydes (or Their Derivatives) with Cyclic Anhydrides

ConspectusThe rapid expansion of the global polymer industry has highlighted the urgent need for sustainable alternatives to traditional synthetic polymers, which are predominantly derived from nonrenewable fossil resources and pose significant environmental challenges due to their persistence in ecosystems. In response, the development of chemically recyclable polymers has emerged as a promising strategy to reconcile the utility of polymer materials with the imperative of sustainability. However, the synthesis of such polymers often faces limitations in monomer diversity, polymerization efficiency, and the ability to achieve true chemical recyclability.In this Account, we present a comprehensive overview of our recent advancements in the synthesis of chemically recyclable polyesters through the alternating copolymerization of aldehydes (or their derivatives) with cyclic anhydrides. This approach leverages abundant and cost-effective feedstocks, including aldehydes derived from renewable resources and cyclic anhydrides prepared from biorenewable diacids, to create a versatile platform for sustainable polymer synthesis. By employing a wide range of monomers, we have successfully synthesized over 140 polyesters with highly tunable structures and properties.A key feature of this copolymerization is its chemical reversibility, a thermodynamic characteristic arising from a low reaction enthalpy change. This results in a ceiling temperature behavior, wherein the polymer becomes unstable with respect to its monomers upon heating. This chemical reversibility is the fundamental principle that enables the efficient, closed-loop chemical recycling that we demonstrate. Additionally, the water-degradable properties of certain copolymers, particularly those derived from formaldehyde, offer a pathway for developing polymers that can fully degrade into valuable small molecules in water or seawater. This feature is particularly significant in the context of marine pollution, where traditional plastics persist for centuries. Furthermore, the polyesters derived from Schiff bases exhibited unique self- and autodegradation properties. This tunable degradation behavior, governed by polymer structure, provides a versatile tool for designing materials with tailored life spans. Moreover, the mechanical and flame-retardant properties of polyesters derived from chloral and cyclic anhydrides make them promising alternatives to conventional poly(vinyl chloride).The broader implications of these studies extend beyond the synthesis of sustainable polyesters. By demonstrating the feasibility of utilizing renewable resources for polymer production, we contribute to the development of a circular economy, where materials are designed with their end-of-life considerations in mind. Future research will focus on expanding the scope of monomers, optimizing polymerization conditions, and integrating these materials into industrial processes.