Depolymerization of Polycarbonates by Transesterification without Using Base, Ionic Liquid, and Additives

Abstract La(III)‐catalyzed depolymerization of polycarbonates produces the raw carbonates and diols by transesterification without the use of bases, ionic liquids or additives. Poly(bisphenol A carbonate) ( 1 a ) is depolymerized by [La(acac) 3 ] (acac: acetylacetonate) (1 mol %) in MeOH at 135 °C for 20 min to give dimethyl carbonate ( 2 a ) (95 %) and bisphenol A ( 3 a ) (93 %). This reaction can also be carried out in the air using MeOH as received and on a 10 gram‐scale. A commercial compact disk (CD) can also be depolymerized quantitatively. Depolymerization of 1 a in EtOH or 1,2‐propanediol produces corresponding carbonate with 3 a . Poly(ethylene carbonate) ( 1 b ) and poly(propylene carbonate) ( 1 c ) are converted into dimethyl carbonate and corresponding glycols in high yields in MeOH. The kinetic study suggests the surface reaction mechanism for the La(III)‐catalyzed depolymerization of 1 a .