Heteronuclear, Monomer-Selective Zn/Y Catalyst Combines Copolymerization of Epoxides and CO2 with Group-Transfer Polymerization of Michael-Type Monomers

Merging σ-Bond Metathesis with Polymerization Catalysis: Insights into Rare-Earth Metal Complexes, End-Group Functionalization, and Application Prospects

Polymers with well-defined structures, synthesized through metal-catalyzed processes, and having end groups exhibiting different polarity and reactivity than the backbone, are gaining considerable attention in both scientific and industrial communities. These polymers show potential applications as fundamental building blocks and additives in the creation of innovative functional materials. Investigations are directed toward identifying the most optimal and uncomplicated synthetic approach by employing a combination of living coordination polymerization mediated by rare-earth metal complexes and C-H bond activation reaction by σ-bond metathesis. This combination directly yields catalysts with diverse functional groups from a single precursor, enabling the production of terminal-functionalized polymers without the need for sequential reactions, such as termination reactions. The utilization of this innovative methodology allows for precise control over end-group functionalities, providing a versatile approach to tailor the properties and applications of the resulting polymers. This perspective discusses the principles, challenges, and potential advancements associated with this synthetic strategy, highlighting its significance in advancing the interface of metalorganic chemistry, polymer chemistry, and materials science.

A sustainable approach for the synthesis of recyclable cyclic CO2-based polycarbonates

It is highly desirable to reduce the environmental pollution related to the disposal of end-of-life plastics. Polycarbonates derived from the copolymerization of CO2 and epoxides have attracted much attention since they can enable CO2-fixation and furnish biorenewable and degradable polymeric materials. So far, only linear CO2-based polycarbonates have been reported and typically degraded to cyclic carbonates. Here we synthesize a homogeneous dinuclear methyl zinc catalyst ((BDI-ZnMe)2, 1) to rapidly copolymerize meso-CHO and CO2 into poly(cyclohexene carbonate) (PCHC) with an unprecedentedly cyclic structure. Moreover, in the presence of trace amounts of water, a heterogeneous multi-nuclear zinc catalyst ((BDI-(ZnMe2·xH2O)) n , 2) is prepared and shows up to 99% selectivity towards the degradation of PCHC back to meso-CHO and CO2. This strategy not only achieves the first case of cyclic CO2-based polycarbonate but also realizes the complete chemical recycling of PCHC back to its monomers, representing closed-loop recycling of CO2-based polycarbonates.

Synthesis, Characterization, and Catalytic Study of Amine-Bridged Bis(phenolato) Co(II) and Co(II/III)-M(I) Complexes (M = K or Na)

Co(II) complexes 1-3 bearing amine-bridged bis(phenolato) complexes have been synthesized through reactions of bis(phenols) with CoCl₂ or Co(OAc)₂. Oxidation of the Co(II) complex with air resulted in partial oxidation, generating mixed valence Co(II/III) complexes 4 and 5. In addition, due to the presence of alkali compounds (KOAc and NaOMe), 4 and 5 formed as Co-alkali metal heterometallic complexes, which are the first example of mixed valence Co(II/III)-M(I) (M = K or Na) complexes. Complexes 1-5 showed good activity in the cycloaddition of epoxides and CO₂ under atmospheric pressure, generating cyclic carbonates in 40-99% yields. Co(II/III)-Na(I) complex 5 performed better in reactions of bulkier substrates, underlining the enhanced activity of mixed valence Co-alkali metal heterometallic complexes. On the contrary, complex 5 showed limited activity in copolymerization of epoxide and CO₂.

Recent Developments in Ring-Opening Copolymerization of Epoxides With CO2 and Cyclic Anhydrides for Biomedical Applications

The biomedical applications of polyesters and polycarbonates are of interest due to their potential biocompatibility and biodegradability. Confined by the narrow scope of monomers and the lack of controlled polymerization routes, the biomedical-related applications of polyesters and polycarbonates remain challenging. To address this challenge, ring-opening copolymerization (ROCOP) has been exploited to prepare new alternating polyesters and polycarbonates, which would be hard to synthesize using other controlled polymerization methods. This review highlights recent advances in catalyst development, including the emerging dinuclear organometallic complexes and metal-free Lewis pair systems. The post-polymerization modification methods involved in tailoring the biomedical functions of resultant polyesters and polycarbonates are summarized. Pioneering attempts for the biomedical applications of ROCOP polyesters and polycarbonates are presented, and the future opportunities and challenges are also highlighted.

Epoxy-functionalised 4-vinylguaiacol for the synthesis of bio-based, degradable star polymers via a RAFT/ROCOP strategy

An epoxy derivative of a naturally occuring vinylphenolic compound, 4-vinylguaiacol, was polymerised using a RAFT/ROCOP strategy and produced ester cross-linked star polymers which could be selectively degraded under acid conditions.