Switchable Polymerization Triggered by Fast and Quantitative Insertion of Carbon Monoxide into Cobalt-Oxygen Bonds.
Angew Chem Int Ed Engl
; 59(15): 5988-5994, 2020 Apr 06.
Article
em En
| MEDLINE
| ID: mdl-32017360
ABSTRACT
A strategy that uses carbon monoxide (CO) as a molecular trigger to switch the polymerization mechanism of a cobalt Salen complex [salen=(R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine] from ring-opening copolymerization (ROCOP) of epoxides/anhydrides to organometallic mediated controlled radical polymerization (OMRP) of acrylates is described. The key phenomenon is a rapid and quantitative insertion of CO into the Co-O bond, allowing for in situ transformation of the ROCOP active species (Salen)CoIII -OR into the OMRP photoinitiator (Salen)CoIII -CO2 R. The proposed mechanism, which involves CO coordination to (Salen)CoIII -OR and subsequent intramolecular rearrangement via migratory insertion has been rationalized by DFT calculations. Regulated by both CO and visible light, on-demand sequence control can be achieved for the one-pot synthesis of polyester-b-polyacrylate diblock copolymers (D<1.15).
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01-internacional
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MEDLINE
Idioma:
En
Ano de publicação:
2020
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Article