Chaotrope-assisted aqueous depolymerization of polycarbonate with spontaneous catalyst regeneration

Abstract

Aqueous chemical recycling of condensation polymers represents an ideal pathway for a circular economy, yet its implementation is severely hindered by the profound hydrophobic barrier at the polymer-water interface. Herein, we report a chaotropic salt-assisted aqueous depolymerization system that overcomes this limitation. We demonstrate that chaotropic ions (e.g., guanidinium) enhance wetting and polymer-water interfacial accessibility of hydrophobic polycarbonate (PC), thereby enabling efficient depolymerization over an Fe/MgO catalyst under mild conditions (100°C, 1 atm). While conventional batch recycling leads to catalyst deactivation via densification of carbonate species, we discovered that transitioning to an in situ one-pot sequential-feeding process promotes carbonate-mediated surface renewal and improves long-term catalyst stability. Detailed structural analysis reveals that the reaction-derived carbonate ions drive the selective surface segregation of iron species, forming active Fe2O3 nanoparticles on the catalyst exterior. This process effectively turns the typically detrimental phase transformation into a beneficial surface renewal mechanism. Consequently, the system achieved long-term stability (>10 days) processing a cumulative polymer load exceeding 100 times the catalyst mass with quantitative conversion and high monomer yield.