Organocatalytic Alternating Copolymerization of CO2/Epoxide/Anhydride for Synthesis of Polycarbonate/Polyester Copolymers

The synthesis of environment-friendly polymer materials, including polycarbonates and polyesters, supports the strategy of sustainable development, and it is also one of the feasible ways to solve the current environmental stress (greenhouse effect and white pollution, etc.). Carbon dioxide (CO2) has a wide range of sources and is non-toxic, but it could cause the greenhouse effect. Therefore, developing efficient techniques to transform CO2 into value-added chemicals is a promising solution for our sustainable society. CO2-based polycarbonate materials can be prepared by ring-opening alternating copolymerization (ROCOP) of CO2 and epoxide, while polyester materials can be prepared by ROCOP of epoxide and anhydride. Organocatalysts, as a type of emerging metal-free catalysts, have developed rapidly in the past 20 years and exhibited unique properties and exceptional promises for various polymerization reactions. Recently, our group have developed a series of organic phosphazenes, which are a family of extremely strong, non-nucleophilic, and uncharged auxiliary bases and show remarkable potential as organocatalysts for ring-opening polymerization (ROP) of cyclic monomers. On the other hand, phosphazenes in combination with a Lewis acid, such as triethyleborane (TEB), can easily construct diverse binary organocatalysts that exhibite excellent catalytic performances. Apparently, organocatalytic synthesis of polymer materials has become an important and hot research topic. This feature article reviews the recent progress in the field of ROCOP of CO2/epoxide/anhydride catalysed by organocatalysts followed by a proper discussion of respective polymerization mechanisms. The review includes three sub-topics, i.e., ROCOP of CO2/epoxide, ROCOP of epoxide/anhydride, and terpolymerization of CO2/epoxide/anhydride. A short perspective viewpoint is provided at the end for readers who are interested in this area. [GRAPHICS]

Automated summary

The synthesis of environment-friendly polymer materials is crucial for sustainable development and addressing environmental stress. Organocatalysts, as emerging metal-free catalysts, have unique properties and great potential. This article reviews the recent progress in CO2/epoxide/anhydride ring-opening copolymerization catalyzed by organocatalysts and discusses the respective polymerization mechanisms.