Sustainable and Orthogonally Closed-Loop Recyclable Acetal-Based Long-Chain Polyesters
Xiaomeng Li, Zhitao Hu, Mengxue Zhang, Morgan Stefik, Colleen N. Scott, Chuanbing Tang
Abstract
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.