Sustainable and Orthogonally Closed-Loop Recyclable Acetal-Based Long-Chain Polyesters

It is an emerging trend to develop biobased polymers to mimic commodity plastics. New physical and chemical functions are critically needed. We report a strategy for synthesizing long-chain aliphatic poly(ester)acetals (PEAc) with orthogonal degradability. The synthesis involves a two-step process: polycondensation of C18-diester with aliphatic diols to yield telechelic polyester oligomers, followed by polytransacetalization with diethoxymethane. The resulting polymers exhibit mechanical properties comparable to low-density polyethylene. Furthermore, orthogonal depolymerization is selectively controlled by varied conditions: acetal cleavage under acidic conditions, ester hydrolysis under basic conditions, and complete degradation under neutral conditions. Repolymerization largely confirmed the feasibility of closed-loop recycling. The orthogonally addressable architecture enables a distinctive "oligomer-polymer-oligomer" recycling pathway, circumventing the high-energy input and purification demands of conventional "monomer-polymer-monomer" cycles. In addition to recyclability, the poly(ester)acetals exhibit strong adhesion and adhesive reusability on polar substrates such as steel and wood, with shear strength up to 17 MPa, a property that polyethylene does not have. This study provides a promising route for manufacturing high-performance, orthogonally recyclable polymers mimicking polyethylene and beyond.