Hydrogenated polyethylene terephthalate as a versatile macromolecular platform synthon for waste plastic refineries

Abstract

Inspired by the platform-molecule concept central to modern biorefineries, we propose a polymer-editing approach based on backbone and side-chain modifications that activate inherent functional motifs in commodity plastics, enabling programmable cascade transformations to convert polymeric scaffolds into tailored small molecules, functional oligomers, and advanced materials. Using hydrogenated poly(ethylene terephthalate) (PECHD) as a paradigmatic “backbone-preedited” synthon, we efficiently transform waste PET into trans-enriched 1,4-cyclohexanedicarboxylic acid (CHDA), its mono- and diesters, and cycloaliphatic oligodiols that act as tunable precursors for degradable polyurethane elastomers. Mechanistic and kinetic studies indicate that the semi-rigid alicyclic backbone and ester linkages of PECHD promote specific reaction pathways, resulting in lower energy barriers for selective ester cleavage and facilitating efficient diverse hydrogenation–depolymerization cascades. Additionally, through side-chain editing, polystyrene (PS) is converted—via its hydrogenated intermediates—into cyclohexanone and polyethylene-like polyketones through tandem hydrogenation–oxidation. Collectively, this work establishes a flexible molecular editing strategy that enables stereoselective and catalytically programmable refunctionalization of polymer architectures, providing versatile, scalable, and sustainable design principles for a circular plastic economy.