Synthesis of block copolymer of vinyl acetate and methyl acrylate by cobalt-mediated radical polymerization in a packed column system: simultaneous control of molecular weight, separation, and purification

In this study, for the first time, we investigate cobalt-mediated radical block copolymerization of vinyl acetate (VAc) and methyl acrylate (MA) in a packed column system in the presence of cobalt((II)) acetylacetonate (Co (acac)(2)) as a controlling agent. This copolymerization system has the capability to remove the residual catalyst and separate copolymers with different molecular weights, simultaneous to polymerization. Synthesis of high-purity poly (vinyl acetate)-b-poly(methyl acrylate-co-vinyl acctate) (PVAc-b-P(MA-co-VAc)) copolymers were successfully performed by initiating the radical copolymerization of MA and VAc from PVAc-Co (acac)(2) macroinitiator in the packed column with silica gel particles. Copolymerization reaction proceeds via a controlled characteristic with first-order kinetics with respect to monomers, predetermined molecular weight, and relatively narrow molecular weight distribution. GPC, (HNMR)-H-1, and DSC analyses demonstrated that the PVAc-b-P(MA-co-VAc) was formed with a blocky structure. Based on the analyses, it was found that the VAc content in the block copolymer progressively increased with increasing conversion in the constant VAc initial ratio, indicating that the second block copolymer had a gradient sequence distribution. Moreover, the VAc and MA reactivity ratios in the packed column with silica gel particles were calculated using the extended Kelen-Tudos method to be r(MA) = 4.98 and r(VAc) = 0.62, respectively.