Construction of Well-Defined Redox-Responsive CO2 -Based Polycarbonates: Combination of Immortal Copolymerization and Prereaction Approach.

Due to the axial group initiation in traditional (salen)CoX/quaternary ammonium catalyst system, it is difficult to construct single active center propagating polycarbonates for copolymerization of CO2 /epoxides. Here a redox-responsive poly(vinyl cyclohexene carbonate) (PVCHC) with detachable disulfide-bond backbone is synthesized in a controllable manner using (salen)CoTFA/[bis(triphenylphosphine)iminium, [PPN]TFA binary catalyst, where the axial group initiation is depressed by judiciously choosing 3,3'-dithiodipropionic acid as starter. While for those comonomers failing to obtain polycarbonate with unimodal gel permeation chromatography (GPC) curve, a versatile method is developed by combination of immortal copolymerization and prereaction approach, and functional aliphatic polycarbonates having well-defined architecture and narrow polydispersity can be prepared. The resulting PVCHC can be further functionalized with alkenes by versatile cross-metathesis reaction to tune the physicochemical properties. The combination of immortal polymerization and prereaction approach creates a powerful platform for controllable synthesis of functional CO2 -based polycarbonates.

One-pot atom-efficient synthesis of bio-renewable polyesters and cyclic carbonates through tandem catalysis.

One-pot synthesis of well-defined bio-renewable polyesters and cyclic carbonates in high yields was successfully realized for the first time by way of a tandem reaction using metal salen complexes as catalysts. This tandem process offered unprecedented opportunities for the atom-efficient production of two relevant compounds.

Carbon dioxide-based copolymers: environmental benefits of PPC, an industrially viable catalyst.

Carbon dioxide-based copolymers utilize the green house gas CO(2) and can be applied in research and industry. Here we focus on industrially viable CO(2)-based catalysts in China and beyond. Poly(propylene carbonate) (PPC), an alternating copolymer of CO(2) and propylene oxide, is one of the emerging low-cost biodegradable plastics. We describe the thermal and mechanical performances of as-polymerized PPC, where amorphous state, low glass transition temperature, and biodegradability are the three main properties. We also describe modification of the PPC, the so-called toughening and strengthening at high temperature, and plasticizing at low temperature, including incorporation of a third monomer unit by chemical terpolymerization, and introduction of special intermolecular interactions or crystallizable components by physical blending. The fast development in catalyst design and performance improvement for PPC has created new chances for industry. In particular, high molecular weight PPC from rare earth ternary catalyst is becoming an economically viable biodegradable plastic with tens of thousands of tons produced per year, providing a new solution to overcome the problem of high cost in biodegradable plastics.