Multi-Pathway Chemical Recycling of Bio-Based Polycarbonates Containing Spirocyclic Acetal Structures

The current plastic economy heavily relies on nonrenewable fossil-based feedstocks and hence urgently needs to transition to a circular economy. This shift necessitates the utilization of renewable feedstocks for plastics manufacturing and the implementation of end-of-life strategies to promote sustainability. In this study, we present the synthesis and characterization of biobased polycarbonates containing spirocyclic acetals, which allow for multipathway and orthogonal chemical recycling. These polymers, prepared via two distinct synthetic routes, exhibit excellent thermal properties due to their rigid structures, with Tg values ranging from 154 to 192 °C. Notably, the molecular design of these poly(acetal-carbonate)s facilitates efficient and selective depolymerizations under both acidic and basic conditions through hydrolysis and transesterification, respectively, thus providing a dual closed-loop recycling system. By introducing different nucleophiles, poly(acetal-carbonate)s additionally allow for upcycling into value-added carbonate or urea derivatives. This strategic multipathway chemical recycling approach, aiming at obtaining various monomeric compounds through depolymerization, opens the door to the creation of new generations of sustainable polymer products. This advancement in circular material design emphasizes the significance of effectively managing the end-of-life stages of plastics.