Calorimetric investigation of polymerization reactions. I. Diffusion‐controlled polymerization of methyl methacrylate and styrene

Abstract

AbstractThe rate of bulk polymerization of methyl methacrylate and styrene was determined directly, continuously and over the whole range of conversion with a differential scanning calorimeter (DSC) operated isothermally. At the later stages of the accelerated polymerization of methyl methacrylate, a previously unknown inflection or peak in the rate of polymerization was observed. The variation of the rate after the onset of the gel effect, including this peculiar inflection, was interpreted on the basis of the diffusion behavior of monomer molecules and polymeric radicals in the polymer–monomer system, their diffusion rates being predicted from the free volume theory. The final conversion at which no further polymerization proceeds was determined for both monomers. It was affirmed quantitatively that the final conversion has a close relation with the transition of the polymer–monomer system from a viscous liquid to a glassy state.