It is of great significance to depolymerize used or waste polymers to recover the starting monomers suitable for repolymerization reactions that reform recycled materials no different from the virgin polymer. Herein, we report a novel recyclable plastic: degradable polycarbonate synthesized by dinuclear chromium-complex-mediated copolymerization of CO with 1-benzyloxycarbonyl-3,4-epoxy pyrrolidine, a meso-epoxide. Notably, the novel polycarbonate with more than 99 % carbonate linkages could be recycled back into the epoxide monomer in quantitative yield under mild reaction conditions. Remarkably, the copolymerization/depolymerization processes can be achieved by the ON/OFF reversible temperature switch, and recycled several times without any change in the epoxide monomer and copolymer. These characteristics accord well with the concept of perfectly sustainable polymers.

The environmental impact of industrially important plastics can be minimized by using renewable feedstocks and preparing biodegradable polymers. A significantly more meaningful strategy is the utilization of alternating copolymerization of epoxides and cyclic anhydrides or lactone or CO 2 to provide degradable polyesters or polycarbonates. Herein, we report a versatile and efficient catalyst system based on dinuclear chromium complex bearing biphenol linking bridge for copolymerizing epoxides with cyclic anhydrides or CO 2 or dihydrocoumarin (DHC), affording various degradable copolymers with perfectly alternating structure and narrow molecular weight distribution. Most of the polyesters from DHC are typical semicrystalline materials, being beneficial to the potential application of aliphatic polyesters as structural materials. Notably, this dinuclear chromium catalyst system was also discovered to be very efficient in the one-pot terpolymerization of cyclohexene oxide/phthalic anhydride/CO 2 , cyclohexene oxide/phthalic anhydride/DHC, or cyclohexene oxide/CO 2 /DHC, providing polyester-b-polycarbonate, polyester-b-polyester, or poly(ester-random-carbonate), respectively. This approach is valuable for the preparation of various novel materials with tailored property and functionality.

It is of great significance to depolymerizeu sed or waste polymers to recover the starting monomers suitable for repolymerization reactions that reform recycled materials no different from the virgin polymer.H erein, we report an ovel recyclable plastic:d egradable polycarbonate synthesized by dinuclear chromium-complex-mediated copolymerization of CO 2 with 1-benzyloxycarbonyl-3,4-epoxy pyrrolidine,amesoepoxide.N otably,t he novel polycarbonate with more than 99 %c arbonate linkages could be recycled backi nto the epoxide monomer in quantitative yield under mild reaction conditions.R emarkably,t he copolymerization/depolymerization processes can be achieved by the ON/OFF reversible temperature switch,a nd recycled several times without any change in the epoxide monomer and copolymer.T hese characteristics accord well with the concept of perfectly sustainable polymers.Supportinginformation for this article can be found under: http://dx.