High conversion polymerisation of vinyl systems. I. Methyl methacrylate

Abstract

Abstract The polymerisation of methyl methacrylate has been studied over the complete course of the reaction and an attempt has been made to explain the characteristics of the “gel effect” observed in the high conversion polymerisation of this and other vinyl systems. It is suggested that in the bulk polymerisation of this vinyl ester stationary state kinetic are only strictly applicable in the early stages of polymerisation, after which the accumulated polymer results in the occlusion of growing radicals. Thus when there is a decrease in the concentration of radicals available for termination there is an increase in the number capable of further propagation. The result is a continual increase in the rate of polymesation and in the molecular weight of polymer formed. Similarly the sharp fall off in rate to zero values before complete polymerisation, has been explained by a decrease in the rate of propagation due to the inability of monomer to diffuse readily through the highly gelled system. A simple kinetic analysis has been put forward explaining the “T ROMSDORFF ‐Effect” as a radical concentration phenomenon, and for methacrylate esters this gives good agreement with experimental observations. Determinations of the intensity exponent of the reaction and the effect of transfer agents on the polymerisation are also in good agreement with the theories proposed.