Chemical Recycling of Poly(Cyclohexene Carbonate) Using a Di‐Mg^II Catalyst

Abstract

Chemical recycling of polymers to true monomers is pivotal for a circular plastics economy. Here, the first catalyzed chemical recycling of the widely investigated carbon dioxide derived polymer, poly(cyclohexene carbonate), to cyclohexene oxide and carbon dioxide is reported. The reaction requires dinuclear catalysis, with the di‐MgII catalyst showing both high monomer selectivity (>98 %) and activity (TOF=150 h−1, 0.33 mol %, 120 °C). The depolymerization occurs via a chain‐end catalyzed depolymerization mechanism and DFT calculations indicate the high selectivity arises from Mg‐alkoxide catalyzed epoxide extrusion being kinetically favorable compared to cyclic carbonate formation.

Post-polymerization functionalization of aliphatic polycarbonates using click chemistry

“…This is due to the higher activation barrier for cyclic carbonate production, 53 as well as more favorable thermodynamic stability of the copolymer vs. cyclic carbonates. 54,55 In this regard, copolymers from VCHO and CO 2 were synthesized and modified employing thiol–ene click chemistry with β-mercaptoethanol to provide side chains with –OH end groups. In a sequential process, ε-caprolactone was grafted onto these –OH groups via ring-opening polymerization to afford degradable well-defined brush polymers.…”

“…This is due to the higher activation barrier for cyclic carbonate production, 53 as well as more favorable thermodynamic stability of the copolymer vs. cyclic carbonates. 54,55 In this regard, copolymers from VCHO Scheme 3 Sequential approach for the synthesis and functionalization of polycarbonates. (a) Water-mediated polycarbonate synthesis and functionalization to achieve amphiphilic polycarbonates.…”

Current Challenges and Perspectives in CO2-Based Polymers

“…Zhang and Williams independently reported the selective depolymerization of PCHC to CHO monomer for the first time, mediated by bimetallic zinc complex 9c and magnesium complex 10 (Mg II –Mg II ) in solution (Figure , route c). Indeed, most chemical recycling reactions were performed in an organic solution with an extremely low polymer concentration. , This significantly restricted the practical applications.…”

Suspended Alicyclic Skeleton: Synthetic Approach to Zero-Birefringence Polycarbonate

“…PCHC is a well-known polymer synthesized by alternating the copolymerization of cyclohexene oxide with carbon dioxide using various catalysts. − However, its optical properties, including birefringence, have not been clarified yet. Ring-opening polymerization of lactones and cyclic carbonates has been studied to obtain polyesters and polycarbonates, − and PCHC can also be synthesized by the anionic ring-opening polymerization of trans -1,2-cyclohexene carbonate ( 1 ). − PCHC is both recyclable and sustainable, capable of being quantitatively converted into cyclic carbonate 1 via depolymerization in the presence of some catalysts. − In a previous study, we obtained a high-molecular-weight film-forming PCHC via the anionic ring-opening polymerization of cyclic carbonate 1 and demonstrated its low birefringence . Generally, among birefringence, the orientational birefringence originating from the orientation of the polymer chain can be reduced by annealing.…”