Cobalt‐Mediated Switchable Catalysis for the One‐Pot Synthesis of Cyclic Polymers

Abstract

A cobalt salen pentenoate complex [salen = (R,R)-N,N'-bis(3,5-di-tertbutylsalicylidene)-1,2-cyclohexanediamine] is rationally designed as the catalyst for the ring-opening copolymerization (ROCOP) of epoxides/anhydrides/CO 2 . Via migratory insertion of carbon monoxide (CO) into the Co À O bonds, the ROCOP-active species a-alkene-w-O-Co III (salen) can be rapidly and quantitatively transformed into a-alkene-w-O 2 C-Co III (salen) telechelic linear precursors. Upon dilution of reaction mixtures, the homolytic cleavage of CoÀC bonds induced by visible light generates a-alkene acyl radicals that spontaneously undergo intramolecular radical addition to afford organocobalt-functionalized cyclic polyesters and CO 2 -based polycarbonates with excellent regioselectivity. The cyclic products can either react with radical scavengers to generate metal-free cyclic polymers or serve as photo-initiators for organometallic-mediated radical polymerization (OMRP) to produce tadpole-shaped copolymers.

Controlled Synthesis of Cyclic‐Helical Polymers with Circularly Polarized Luminescence

“…For example, cyclic polymers have smaller hydrodynamic volume, lower melt viscosity, higher glass‐transition temperatures, and distinct self‐assembly behavior. In addition, various applications of the polymers have been revealed, such as drug delivery, rheological modifiers, plasticizers, lubricants, polymer building block, supramolecular, and material chemistry [4–11] . The new biological importance of viral cyclic deoxyribonucleic acid (DNA) and plasmids emphasizes and stimulates enthusiasm in the area of cyclic polymers [4] .…”

“…In addition, various applications of the polymers have been revealed, such as drug delivery, rheological modifiers, plasticizers, lubricants, polymer building block, supramolecular, and material chemistry. [4][5][6][7][8][9][10][11] The new biological importance of viral cyclic deoxyribonucleic acid (DNA) and plasmids emphasizes and stimulates enthusiasm in the area of cyclic polymers. [4] Although efforts have been made to overcome the constraints in synthesizing cyclic polymers, available strategies for the efficient and scalable synthesis of cyclic polymers are limited.…”

Cyclic polymers: synthesis, characteristics, and emerging applications

“…38 Very recently, Wang and coworkers designed a cobalt salen pentenoate catalyst that can be used for one-pot ring-opening copolymerization of epoxides/anhydrides/CO 2 and intramolecular cyclization, generating well-defined cyclic polyesters and CO 2 -based polycarbonates. 39…”

Switchable Polymerization: A Practicable Strategy to Produce Biodegradable Block Copolymers with Diverse Properties

“…Polydecalactone-poly(cyclohexene phthalate)-poly (phthalic anhydride) [56] Poly(cyclohexene carbonate)-poly(deca-lactone)-poly (cyclo-hexene carbonate) [76] Poly(propylene phthalate)-poly(methyl acrylate) [78] Figure 1. Multiple characters of materials from switchable polymerization.…”