Chemical Upcycling of Poly(bisphenol A carbonate) to Diglycerol Dicarbonate: A Strategy to Repurpose Polycarbonates to Polyurethanes Using Biobased Diglycerol

The chemical recycling of poly(bisphenol A carbonate) (BPA-PC) was studied with biobased diglycerol as a depolymerizing agent in order to form diglycerol dicarbonate (DGDC) and bisphenol A. The reaction was first investigated with pure α,α-diglycerol. The reaction was catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) under relatively mild conditions (2-MeTHF, 50 °C). Under these conditions, diglycerol dicarbonate was obtained with an 86% isolated yield, while bisphenol A was recovered with 92% yield. A technical mixture of diglycerol, mainly containing α,α- and α,β-isomers, was also used for the depolymerization of BPA-PC. In that case, the yield of DGDC reached 75%, demonstrating the feasibility of preparing this key compound from the mixture of diglycerol and thus improving the economic viability of this process. The chemical depolymerization of waste materials containing BPA-PC was also studied under the optimized conditions. Overall, considering that DGDC is a key monomer for the preparation of nonisocyanate polyurethanes (NIPUs), its production from BPA-PC and biobased diglycerol offers a strategy to repurpose waste polycarbonates to polyurethanes while recovering the original BPA monomer.