Closed-loop recycling of semi-aromatic polyesters upcycled from poly(ethylene terephthalate)
Jeffrey C. Foster, Jackie Zheng, Md Arifuzzaman, Md Anisur Rahman, Joshua T. Damron, Chao Guan, Ilja Popovs, Nick Galan, Zoriana Demchuk, Tomonori Saito
Abstract
Plastics are critical in facilitating the comfort and quality of everyday life. Most plastics are discarded after a single use, wasting the energy and carbon consumed for their production and incurring environmental costs. Thus, closed-loop production and recycling processes are needed to mitigate energy and carbon loss toward a net-zero carbon economy. Here, we show that poly(ethylene terephthalate) (PET) can be efficiently deconstructed into small-molecule α,ω-dialkenenyl terephthalates using organocatalyzed transesterification. The resulting compounds can be polymerized by acyclic diene metathesis (ADMET) polymerization, affording unsaturated semi-aromatic polyesters with thermomechanical properties dependent on the monomer structure and the catalyst used for their synthesis. High-molecular-weight ADMET polymers form free-standing films that are ductile and tough with mechanical properties similar to widely used commodity plastics. Crucially, the ADMET polymers can be deconstructed to monomers using Retro-ADMET and re-polymerized by ADMET polymerization, establishing closed-loop circularity for a unique class of materials.