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/rMA = 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 [Kassn = 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.