Chemoselective depolymerization of polyurethane via solvent-engineered glycolysis

The chemical upcycling of polyurethane (PU) into virgin-quality feedstocks is hindered by toxic toluene diamine (TDA) formation during high-temperature glycolysis. Decoupling selective urethane cleavage from secondary thermolytic pathways remains a central engineering challenge. Here, we present a chemoselective depolymerization strategy utilizing solvent-system synergy. Systematic evaluation of binary-glycol environments identifies a 6 : 4 monoethylene-to-diethylene glycol ratio that balances high nucleophilicity with moderated oligomer solvation. By mapping the multivariable operational space, we define a constrained kinetic window-comprising 1 : 1 glycol-to-PU ratio, 1 mM diethanolamine catalyst, and a 160 °C thermal threshold-that maximizes urethane scission while arresting hard-segment fragmentation. This framework produces high-quality, single-phase glycolysate with minimized TDA concentrations (2278 mg kg^-1). Predictive toxicological modeling confirms this refined product enables up to 40% substitution into secondary PU formulations without exceeding acute aquatic mortality thresholds. Integrating molecular-level solvent design with macroscopic process control provides a scalable, low-toxicity pathway for commercially viable circularity of polyurethane materials.