Multi-Pathway\nChemical Recycling of Bio-Based Polycarbonates\nContaining Spirocyclic Acetal Structures

The current plastic economy heavily relies on nonrenewable\nfossil-based\nfeedstocks and hence urgently needs to transition to a circular economy.\nThis shift necessitates the utilization of renewable feedstocks for\nplastics manufacturing and the implementation of end-of-life strategies\nto promote sustainability. In this study, we present the synthesis\nand characterization of biobased polycarbonates containing spirocyclic\nacetals, which allow for multipathway and orthogonal chemical recycling.\nThese polymers, prepared via two distinct synthetic routes, exhibit\nexcellent thermal properties due to their rigid structures, with <i>T</i><sub>g</sub> values ranging from 154 to 192 °C. Notably,\nthe molecular design of these poly(acetal-carbonate)s facilitates\nefficient and selective depolymerizations under both acidic and basic\nconditions through hydrolysis and transesterification, respectively,\nthus providing a dual closed-loop recycling system. By introducing\ndifferent nucleophiles, poly(acetal-carbonate)s additionally allow\nfor upcycling into value-added carbonate or urea derivatives. This\nstrategic multipathway chemical recycling approach, aiming at obtaining\nvarious monomeric compounds through depolymerization, opens the door\nto the creation of new generations of sustainable polymer products.\nThis advancement in circular material design emphasizes the significance\nof effectively managing the end-of-life stages of plastics.