Radiation polymerization of methacrylates controlled by a chain transfer catalyst

Resumo

The effect of γ-radiation dose and chain transfer catalyst on polymerization of methyl methacrylate (MMA) and copolymerization of MMA with hydroxyethyl methacrylate or triethylene glycol dimethacrylate has been investigated. The addition of 5 × 10⁻⁴−10⁻³ mol/L of bis[(difluoroboryl) isopropylpyridine dimethylglyoximato]cobalt(II) (Co(II)) makes it possible to produce macromonomers MM_n⁼⁼ bearing terminal double bonds and having a degree polymerization of n = 2−40 and a polydispersity index of 1.05−1.15. It has been found that the degree polymerization of the macromonomers increases with the increasing γ-radiation dose and monomer conversion through the mechanism of the reversible β-cleavage of the terminal unit: R_k^∙ + MM_n⁼ ↔ MM_k+1⁼ + R_n-1^∙ followed by the living polymerization of both radicals. This reaction may compete with the catalytic chain transfer reaction and have a significant effect on the evolution of the molecular weight characteristics of the macromonomers during the course of MMA (co)polymerization.