Solvent-induced competing processes in polycarbonate degradation: depolymerization, chain scission, and branching/crosslinking

Poly(bisphenol A carbonate) (PC) is a massively produced engineering plastic and requires innovative recycling methods at its end of life. In this work, we investigate the chemical degradation of PC in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), catalyzed by copper sulfide nanoparticles (CuS NPs). In DMF, PC is degraded to bisphenol A (BPA) via hydrolytic decomposition with an appreciable yield of similar to 80%. In contrast, the degradation of PC in DMSO yields oligomeric or branched/crosslinked PC, possibly due to radical-assisted chain cleavage. Temperature and solution heterogeneity are two parameters that dictate the competition between chain scission and branching/crosslinking. The different degradation behaviors of PC in DMF and DMSO highlight the importance of solvents in polymer degradation, which can lead to different pathways of hydrolytic depolymerization or radical-assisted chain scission, branching, and crosslinking. This work provides new insight into the recycling of plastic waste and offers new avenues to induce polymer branching/crosslinking.