Effect of Ligand and n-Butyl Acrylate on Cobalt-Mediated Radical Polymerization of Vinyl Acetate

Abstract

The electron-withdrawing effect of the ligand in the cobalt complex was studied in cobalt-mediated radical polymerization of vinyl acetate (VOAc) initiated by 2,2‘-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70). The polymerization of VOAc with V-70 and a series of bis(acetylacetonate)cobalt derivatives, Co(R1COCHCOR2)2 (R1 = R2 = CH3 (1), R1 = CF3, R2 = CH3 (2), R1 = R2 = CF3 (3)), was conducted under the same conditions. Complexes 1 and 2 successfully mediated the radical polymerization of VOAc, resulting in poly(VOAc) with predetermined Mn and low polydispersity. In contrast, complex 3 did not control the radical polymerization of VOAc, resulting in poly(VOAc) with higher molecular weight and higher polydispersity. While complex 1 was not able to control the radical polymerization of n-butyl acrylate (nBA), the copolymerization of nBA with various amounts of VOAc (9%, 23%, and 50%) in the presence of V-70 and 1 showed that Mn and Mw/Mn of copolymers decreased with increasing VOAc ratio. This indicat...