Method for Determining the Kinetic Parameters in Diffusion-Controlled Free-Radical Homopolymerizations

Abstract

Free-radical homopolymerizations of 2-hydroxyethyl methacrylate (HEMA) and diethylene glycol dimethacrylate (DEGDMA) photoinitiated by 2,2-dimethoxy-2-phenylacetophenone (DMPA) were studied. A novel analytical method for elucidating the free-volume dependencies of the propagation and termination kinetic constants from a single set of kinetic data is developed. The polymerization is divided into four regimes, nondiffusion limited, autoacceleration, reaction−diffusion without propagation limitations, and autodeceleration, in order to glean the parameters that describe the free-volume dependency. The parameters found via this method are used in a concurrently developed model to predict the polymerization rates and kinetic constant evolution throughout the polymerization. The rates and kinetic constants predicted by the model agree well with the experimentally determined rates and kinetic constants.