100% Atom-Economy Efficiency of Recycling Polycarbonate into Versatile Intermediates

This study demonstrates a simple and convenient two-step one-pot, highly efficient process of recycling poly­(bisphenol A carbonate), i.e., PC, into versatile intermediates for polymers such as polyurethanes (PUs). Via a highly efficient and selective amine carbonylation reaction, PC is depolymerized by aliphatic diamines forming hydroxyl-<i>N</i>,<i>N</i>′-diphenylene-isopropylidenyl biscarbamates (hydroxyl DP-biscarbamates) as major interim prepolymers. Both short- and long-chained prepolymers are prepared with their respective diamines, and the prepolymers are chain-extended with commercially available regents such as diisocyanates to produce a variety of PU polymers. Hence, PC is cleaved into pieces of soluble hydroxyl DP-biscarbamates first and then reassembled into new linear polymers without resorting to a separation process. Different from PC-recycling processes reported in the literature, each carbonate group of PC in this new process is fully utilized for making one carbamate group and one hydroxyl terminated intermediate in the absence of catalyst under mild conditions. Most significantly, this process attains 100% atom-economy efficiency and demonstrates the feasibility of converting one functional polymer into another