Modeling termination kinetics in free-radical polymerization using a reduced number of parameters

Abstract

SUMMARY: An approach for modeling chain-length dependent termination rate coefficients is presented. The method is based on the assumption that free-radical chain length may be considered as a continuous variable. As compared to discrete numerical methods, in continuous modeling the number of independent dimensionless parameters can be significantly reduced. As a consequence, for a wide variety of monomers the conversion dependence of k t can be predicted without extensive numerical calculations. The method may also be used to determine polymerization conditions under which simpler models of k t (which neglect effects arising from the dependence of k t on chain length) may be applied. Calculations for methyl methacrylate, styrene, and butyl acrylate bulk polymerizations up to high degrees of monomer conversion show that the impact of chain length on termination varies with conversion and strongly depends on the type of monomer.

An Investigation of Chain Length Dependent Termination and Reaction Diffusion Controlled Termination during the Free Radical Photopolymerization of Multivinyl Monomers

“…CLDT has been modeled extensively in diffusion controlled monovinyl (photo)polymerizations ,,,,,− and, thus, is generally accepted as important during monovinyl polymerization. Recently, a model of multivinyl monomer photopolymerization kinetics that takes into account CLDT was developed to investigate the impact of accounting for CLDT on the reaction kinetics .…”

Coupling Chain Length Dependent and Reaction Diffusion Controlled Termination in the Free Radical Polymerization of Multivinyl (Meth)acrylates

“…Although they have been studied extensively, their complex nature has hindered efforts to establish a comprehensive picture of the polymerization kinetics and all of the mechanisms that underly the kinetics. , One aspect of the termination kinetics that has received significant attention over the past several decades is the role of the size of the reacting radical. Numerous works have explored the existence of a chain length dependent termination (CLDT) mechanism in monovinyl polymerization systems. − The importance of such a mechanism in those polymerizations has achieved widespread acceptance although the specifics of the relationship between chain length and the termination kinetic constant continue to be extensively evaluated. Conversely, the importance of such a mechanism in polymerizations that cross-link has long been overlooked.…”

“…Numerous works have explored the existence of a chain length dependent termination (CLDT) mechanism in monovinyl polymerization systems. [3][4][5][6][7][8][9][10][11][12][13][14][15] The importance of such a mechanism in those polymerizations has achieved widespread acceptance although the specifics of the relationship between chain length and the termination kinetic constant continue to be extensively evaluated. Conversely, the importance of such a mechanism in polymerizations that cross-link has long been overlooked.…”

Using Changes in Initiation and Chain Transfer Rates To Probe the Kinetics of Cross-Linking Photopolymerizations: Effects of Chain Length Dependent Termination

“…Numerous models that include chain length dependent termination mechanisms continue to be developed. These models can be divided into two primary categories: those that focus on the steady-state kinetics of linear polymerization systems − and those that approach the problem via simulation of the pseudostationary kinetics of these systems, i.e., a modeling perspective of pulsed laser polymerization (PLP) − or rotating sector type experiments. In conjunction with theoretical developments, the development and refinement of pulsed laser − and low-frequency pulsed laser , techniques have enabled experimental verification of the influence of chain length on termination.…”