Free-radical copolymerization of vinyl esters using fluoroalcohols as solvents: The solvent effect on the monomer reactivity ratio

Abstract

Free-radical copolymerizations of vinyl acetate (VAc = M1) and other vinyl esters (= M2) including vinyl pivalate (VPi), vinyl 2,2-bis(trifluoromethyl)propionate (VF6Pi), and vinyl benzoate (VBz) with fluoroalcohols and tetrahydrofuran (THF) as the solvents were investigated. The fluoroalcohols affected not only the stereochemistry but also the polymerization rate. The polymerization rate was higher in the fluoroalcohols than in THF. The accelerating effect of the fluoroalcohols on the polymerization was probably due to the interaction of the solvents with the ester side groups of the monomers and growing radical species. The difference in the monomer reactivity ratios (r1, r2) in THF and 2,2,2-trifluoroethanol was relatively small for all reaction conditions and for the monomers tested in this work, whereas r1 increased in the VAc-VF6Pi copolymerization and r2 decreased in the VAc-VPi copolymerization when perfluoro-tert-butyl alcohol was used as the solvent. These results were ascribed to steric and monomer-activating effects due to the hydrogen bonding between the monomers and solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 220–228, 2000