Study of kinetic regularities and mechanism of methyl methacrylate radical polymerization in the presence of orthophosphoric acid

Abstract

Photoinitiated homophase polymerization of methyl methacrylate (MMA) at 25°C in the presence of a complexing agent, orthophosphoric acid (H3PO4), was studied. It was found that in addition to the increase in initial polymerization rates and molecular weights of PMMA the system MMA/H3PO4 reveals postpolymerization that does not retard with time and is accompanied by an increase on average molecular weight. Macroradicals, lifetimes of which grow considerably in the presence of the complexing agent, are shown to be responsible for the termination‐free postpolymerization in this system by the living chain mechanism. The effect of various factors on the kinetics of postillumination polymerization was studied. A drastic decrease in the rate of bimolecular termination of poly(methyl methacrylate) radicals was shown to be related to the change in conformational properties and to the association of propagation chains via complexing with H3PO4. The mechanism of polymerization in this system was discussed.