Mn₂(CO)₁₀-Induced Controlled/Living Radical Copolymerization of Methyl Acrylate and 1-Hexene in Fluoroalcohol: High α-Olefin Content Copolymers with Controlled Molecular Weights

Abstract

A highly active manganese complex [Mn2(CO)10] efficiently induced the controlled/living radical copolymerizations of a conjugated polar vinyl monomer, methyl acrylate (MA), and an unconjugated nonpolar olefin, 1-hexene (1-Hex), in the presence of ethyl 2-iodoisobutyrate (EMA−I) as an initiator under weak visible light at 40 °C to give the copolymers with controlled molecular weights. The further use of protic fluoroalcohols as solvents enhanced the copolymerization without losing the molecular weight control to result in a high 1-Hex content up to 50 mol %, for which the predominant alternating sequences were confirmed by the 13C NMR analysis of the copolymers. The kinetic analysis of the copolymerizations revealed an increase in the reactivity of the MA-radical to the 1-Hex monomer in the fluoroalcohol [1/r MA = 0.49 in (CF3)2CHOH vs 0.081 in toluene], which can be attributed to the 1:1 hydrogen-bonding interaction between the MA unit and the fluoroalcohol as suggested by the 13C NMR analysis of the MA−fluoroalcohol mixtures [K assn = 2.21 L/mol for (CF3)2CHOH]. Thus, a combination of a highly active Mn2(CO)10 catalyst and a protic fluoroalcohol solvent is effective for the alternating controlled/living radical copolymerization of acrylic monomers and α-olefins.

Photochemically Enabled Iodine Degenerative Transfer Controlled Radical Homo- and Block Copolymerization of Vinylidene Fluoride at Ambient Temperatures with Mn2(CO)10and Visible Light

“…Very recently, Mn 2 (CO) 10 was nevertheless employed as a photo-activator of alkyl iodides (IDT) (116)(117)(118), or RAFT reagents (119) in controlled radical photo(co)polymerizations of VAc, acrylates, styrene and alkenes. Here, Mn(CO) 5 • was shown to irreversibly activate the iodine terminated chains or the initiator (102), but the in-situ generated Mn(CO) 5 -I (85) was not involved in the IDT.…”

Acceleration and Selective Monomer Addition during Aqueous RAFT Copolymerization of Ionic Monomers at 25 °C

“…[ 1 ] As well as the widely-studied photochemical [ 2,3 ] and electrochemical [ 4 ] regulation, RDRP can be regulated by non-covalent interactions. Sleiman and coworkers [ 5 ] encoded the chain length and polydispersity of a polymer to a new polymer through hydrogen bonding.…”

Recent developments in metal-catalyzed living radical polymerization

“…[71][72][73][74] The dinuclear manganese complex has been employed to generate radical species from alkyl iodides for organic synthesis of low-molecular weight compounds. In this radical reaction, the dinuclear complex generates a mononuclear manganese radical species [ÁMn(CO) 5 ] under visible light and then abstracts iodine from even secondary and primary alkyl iodides to generate unstable carbon radical species.…”

“…It can also be applicable for the controlled radical copolymerization of MA and 1-hexene, a non-polar olefin without any radical homopolymerizability, resulting in MA-rich copolymers with controlled molecular weights. 73 The additional use of fluoroalcohols as the solvent enhances the copolymerizability to give copolymers with up to 50 mol% content of 1-hexene depending on the conditions. The enhanced copolymerizability can be ascribed to the hydrogen-bonding interaction between the carbonyl group of MA or the growing radical chain end derived from MA, where the highly electron-deficient monomer and radical species preferentially undergo cross-propagation with the more or less electron-rich 1-hexene radical and 1-hexene monomer, respectively.…”