Modeling of diffusion‐controlled reactions in free radical solution and bulk polymerization: Model validation by DSC experiments

Abstract

In this work, a detailed experimental study of diffusion-controlled reactions in free radical polymerization by using differential scanning calorimetry (DSC) was carried out. The systems studied include the methyl methacrylate bulk polymerization as well as the solution and the bulk polymerization of vinyl acetate at a wide range of experimental conditions including initial initiator concentration, reaction temperature, and type and amount of solvent. The conversion data obtained by DSC was successfully simulated by using a mathematical model based on sound principles such as the free volume theory. The estimated parameters, by fitting predictions of this model to conversion data obtained by DSC were found to be in close agreement with the reported parameters in the literature, thus validating both the experimental and theoretical methods used in this work.

Synthesis, characterization and reaction kinetics of PMMA/silver nanocomposites prepared via in situ radical polymerization

“…Finally, at very high conversions, beyond 90%, the reaction rate tends asymptotically to zero and the reaction almost stops before the full consumption of the monomer, thus a glassy state appears and it corresponds to the well known glass-effect. This is attributed to the effect of diffusion-controlled phenomena on the propagation reaction and the reduced mobility of monomer molecules to find a macro-radical and react [40][41][42]. It has been reported, [43] that the presence of nano-particle may influence polymerization kinetics especially in monomers exhibiting strong effect of diffusion phenomena on the reaction kinetics.…”

“…This is the well-known auto-acceleration or gel-effect and is attributed to the effect of diffusion-controlled phenomena on the termination reaction and the reduced mobility of live macro-radicals in order to find one another and react. Therefore, their concentration increases locally, leading in increased reaction rates [41,42]. Afterward, the reaction rate falls significantly and the curvature of the conversion versus time changes.…”

Free Radical Photopolymerization of Multifunctional Monomers

“…During the early stage of polymerization such radicals terminate much faster due to lower diffusional limitations [31]. During the early stage of polymerization such radicals terminate much faster due to lower diffusional limitations [31].…”

Dimethacrylate network formation and polymer property evolution as determined by the selection of monomers and curing conditions

“…The concentration of accessible radicals affects the chain length of propagating radicals at the point of termination. During the early stage of polymerization, short propagating chains display much higher termination rates due to disparities in terms of diffusion rates [46]. Higher initiation rates and propagating radical concentrations lead to shorter chain lengths and therefore, higher conversion values at the gel point since shorter chains, with fewer pendant reactive groups present statistically reduced likelihood for gelation compared with longer chains.…”