Autoacceleration in Bulk Free‐Radical Polymerization: Effect of Chain Transfer

Abstract

AbstractThe model and methodology for estimating diffusion‐controlled rate coefficients for the methyl methacrylate polymerization system reported in Parts I and II of this series is extended to include the chain transfer reaction to an agent (CTA). Theoretical and experimental results exhibit minima in the rate of polymerization curves at low conversions as it is observed in the absence of CTA. Such minima are proposed to be the onset of the autoacceleration effect where the termination reaction undergoes a transition from chemically controlled to diffusion controlled where the segmental mobility of the chain ends plays a key role. As the CTA concentration increases, the conversion at which the minimum is presented is higher and the autoacceleration is less pronounced. This behavior is explained in terms of the effect of polymer chain entanglements and segmental mobility of the chain ends on the termination rate coefficient k t.