Visible light-induced controlled radical polymerization of methacrylates with perfluoroalkyl iodide as the initiator in conjugation with a photoredox catalyst fac -[Ir(ppy)]₃

Abstract

A new visible light‐induced controlled radical polymerization of methacrylate with perfluoro‐1‐iodohexane (CF3(CF2)5I) as the initiator in the presence of a photoredox catalyst (fac‐[Ir(ppy)3]) was developed. Mechanistically, a photoexcited fac‐[Ir(ppy)3]* complex reacted with dormant C‐I species to generate the chain propagating radical and IrIVI complex, which could be reversibly reduced by the propagating radical. The molecular weight (Mn) and the corresponding distribution index (Mw/Mn = 1.4) were controlled in the polymerization of methyl methacrylate (MMA). For the polymerization of functional monomers, such as glycidyl methacrylate (GMA) and trifluoroethyl methacrylate, their monomer conversions could be up to 96 and 94%, respectively. No polymerization reaction took place without external light stimulation, indicating that the system was an ideal photo “on−off” switchable system. Furthermore, a clean diblock copolymer PMMA‐b‐PGMA was successfully synthesized with PMMA‐I as the macroinitiator. With CF3(CF2)5I as the initiator, short CF3(CF2)5− group tags were introduced on the produced polymer chains. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3283–3291

Photocatalysts in Polymerization Reactions

“…This mechanism, oxidative versus reductive, was suggested based on spin‐trapping electron–spin resonance (ESR) experiments and it is directed by the redox potential of the excited‐state Ir III * species, which is dramatically affected by the ligands, and the choice of the alkyl bromide radical initiator . The remarkable activity of [Ir(ppy) 3 ] in photo‐CRP allowed the surface patterning of poly(MMA) to be controlled by visible‐light irradiation, as well as the sequenced polymerization of fluorinated methacrylate monomers, in particular by using perfluoro‐1‐iodohexane as an initiator, and the sequenced polymerization of functional methacrylate monomers synthesized in situ by enzyme catalyzed reactions . In the latter case, in addition to the high performances of Ir III ‐based CRP under soft conditions, the authors noticed that key parameters such as the light intensity, the irradiation source, the Ir III concentration, and residual compounds affected the CRP results .…”

ChemInform Abstract: Photocatalysts in Polymerization Reactions

“…[119] This mechanism, oxidative versus reductive, was suggested based on spin-trappinge lectron-spin resonance (ESR) experiments and it is directed by the redox potential of the excited-state Ir III *s pecies, which is dramatically affected by the ligands, and the choiceo ft he alkyl bromide radical initiator. [119] The remarkable activity of [Ir(ppy) 3 ]i np hoto-CRP allowed the surface patterning of poly(MMA)t ob ec ontrolled by visible-light irradiation, [120] as well as the sequenced polymerization of fluorinated methacrylate monomers, [121] in particularb yu sing perfluoro-1-iodohexane as an initiator, [122] and the sequenced polymerization of functionalm ethacrylate monomers synthesized in situ by enzyme catalyzed reactions. [123] In the latter case, in addition to the high performan-Scheme9.Photoelectron transfer reversible fragmentationc hain transfer (PET-RAFT).…”

Well-controlled atom transfer radical polymerizations of acrylates using recyclable niobium complex nanoparticle as photocatalyst under visible light irradiation

“…The conventional photoinitiated ATRP is based on photoredox reactions of copper catalysts under UV light [28][29][30][31]. Hawker reported Ir-catalyzed visible light mediated ATRP polymerizations [32][33][34]. Choi et al…”