Chemical Synthesis of CO2-Based Polymers with Enhanced Thermal Stability and Unexpected Recyclability from Biosourced Monomers

The development of completely recyclable polymers has become an emerging frontier in polymer chemistry; however, the efficient synthesis of monomers or/and polymers with desirable physical properties and mechanical strengths required for practical uses from renewable feedstocks under environmentally friendly conditions still represents a challenge. Herein, we report five types of completely recyclable polycarbonates made from CO2 and biosourced epoxide featuring different substituents on the carbamate group. It is discovered that the judicious installation of various alkyl substituents can drastically enhance the thermal stability and crystalline capacity of the resultant polymers, while the stable five-membered pyrrolidine ring can execute the complete chemical recyclability. For example, CO2-based polycarbonates with a Bu-t substituent feature with a T-g value of up to 152 degrees C, close to those of the BPA-based polycarbonates and Bu-t-substituted CO2 polycarbonates are thermally stable up to similar to 300 degrees C, while Me- and Bn-substituted copolymers become crystalline. Remarkably, all of the reported CO2-based polycarbonates can be recycled back into the epoxide monomers in quantitative yields under mild conditions. This represents a rare example of a CO2-based polycarbonate featuring biosourced characteristics and unique recyclability.

Automated summary

The study reported five types of completely recyclable polycarbonates made from CO2 and biosourced epoxide, demonstrating enhanced thermal stability and crystalline capacity by installing different alkyl substituents on the carbamate group. All reported CO2-based polycarbonates can be fully recycled back into epoxide monomers under mild conditions, showcasing biosourced characteristics and unique recyclability.