Bicyclic Guanidine Promoted Mechanistically Divergent Depolymerization and Recycling of a Biobased Polycarbonate

We here report the organocatalytic and temperature-controlled depolymerization of biobased poly(limonene carbonate) providing access to its trans-configured cyclic carbonate as the major product. The base TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) offers a unique opportunity to break down polycarbonates via end-group activation or main chain scission pathways as supported by various controls and computational analysis. These energetically competitive processes represent an unprecedented divergent approach to polycarbonate recycling. The trans limonene carbonate can be converted back to its polycarbonate via ring-opening polymerization using the same organocatalyst in the presence of an alcohol initiator, offering thus a potential circular and practical route for polycarbonate recycling. Organocatalytic depolymerization of poly(limonene carbonate) and related macromolecules is reported. The main degradation product, limonene carbonate, can be repolymerized via ring-opening polymerization using the same organocatalyst providing a potential circular process. The mechanistic intricacies of this polymer depolymerization has been scrutinized in detail revealing the concomitant occurrence of complementary and unique degradation modes.+image