Radiation Polymerization of Methacrylates Controlled by a Chain Transfer Catalyst

The effect of gamma- 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 x 10(-4)-10(-3) mol/L of bis[(difluoroboryl) isopropylpyridine dimethylglyoximato] cobalt(II) (Co(II)) makes it possible to produce macromonomers 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 gamma- radiation dose and monomer conversion through the mechanism of the reversible beta- cleavage of the terminal unit: R-k + MMn= <-> MMk+1= + R-n-1(center dot) 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.