Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO₂‐Based Block Copolymers from Monomer Mixtures

Abstract

Switchable polymerization provides the opportunity to regulate polymer sequence and structure in a one‐pot process from mixtures of monomers. Herein we report the use of O2 as an external stimulus to switch the polymerization mechanism from the radical polymerization of vinyl monomers mediated by (Salen)CoIII−R [Salen=N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamine; R=alkyl] to the ring‐opening copolymerization (ROCOP) of CO2/epoxides. Critical to this process is unprecedented monooxygen insertion into the Co−C bond, as rationalized by DFT calculations, leading to the formation of (Salen)CoIII−O−R as an active species to initiate ROCOP. Diblock poly(vinyl acetate)‐b‐polycarbonate could be obtained by ROCOP of CO2/epoxides with preactivation of (Salen)Co end‐capped poly(vinyl acetate). Furthermore, a poly(vinyl acetate)‐b‐poly(methyl acrylate)‐b‐polycarbonate triblock copolymer was successfully synthesized by a (Salen)cobalt‐mediated sequential polymerization with an O2‐triggered switch in a one‐pot process.

Carbon dioxide copolymers: Emerging sustainable materials for versatile applications

“…103 Block copolymerization is also chosen to adjust the performance of PPC, while CO 2 -based block copolymers with various molecular architectures have been designed and synthesized, for example, Wang and coworkers described a one-pot sequential construction of a block copolymer from PO/CO 2 and vinyl monomers by oxygen-triggered switchable polymerization. 104 Another effective way to tune the material property is to form crosslinked networks by interconnecting polymer chains via covalent bonds or ionic bonds, for example, terpolymerization of CO 2 , PO, and allyl glycidyl ether produced UV irradiation cross-linkable PPC with improved mechanical performance. 68 Blending of PPC with other polymers or with inorganic particles is a relatively simple but practical strategy to raise the thermal and mechanical performances of PPC, especially when intermolecular interaction happened.…”

“…For example, Lu and coworkers employed a bifunctional (salen)Co() catalyst for PO/CHO/CO 2 terpolymerization, resulting terpolymers of only one thermolysis peak whose T g was adjustable between 42 and 118°C simply by controlling the molar fraction of PCHC 103 . Block copolymerization is also chosen to adjust the performance of PPC, while CO 2 ‐based block copolymers with various molecular architectures have been designed and synthesized, for example, Wang and coworkers described a one‐pot sequential construction of a block copolymer from PO/CO 2 and vinyl monomers by oxygen‐triggered switchable polymerization 104 . Another effective way to tune the material property is to form cross‐linked networks by interconnecting polymer chains via covalent bonds or ionic bonds, for example, terpolymerization of CO 2 , PO, and allyl glycidyl ether produced UV irradiation cross‐linkable PPC with improved mechanical performance 68 .…”

A journey into metal–carbon bond homolysis

“…It is also of interest to point out that the VAc polymerization has also been controlled by porphyrin [108][109][110] and Schiff-base [111][112][113][114] cobalt(II) complexes. These polymerizations only occur by degenerative exchange, by photoinduced bond cleavage, or by addition of donor ligands, whereas the dissociative thermal activation of the dormant chains is completely inhibited in spite of the high ligand steric bulk in some cases (e.g.…”

Switchable Polymerization Triggered by Fast and Quantitative Insertion of Carbon Monoxide into Cobalt–Oxygen Bonds

“…In a recent contribution, we have illustrated a mechanistic switch involving ROCOP and OMRP with a (Salen)Co system as catalyst/mediator for both mechanisms. The switch operated in the OMRP‐to‐ROCOP direction via a O 2 ‐triggered modification of the polymer chain end from Co−R to Co−OR and was implemented for the development of diblock copolymers with a poly(vinyl acetate) block and a polycarbonate block (by ROCOP of CO 2 /epoxides) . Herein, we report a switch of polymerization mechanism in the opposite direction, from ROCOP of epoxides/anhydrides to OMRP, using carbon monoxide (CO) as a molecular trigger and the (Salen)Co III Cl complex as the mediator (Scheme ).…”