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

An approach for modeling chain-length dependent termination rate coefficien ts is presented. The method is based on the assumption that free-radical ch ain length may be considered as a continuous variable. As compared to discr ete numerical methods, in continuous modeling the number of independent dim ensionless parameters can be significantly reduced. As a consequence, for a wide variety of monomers the conversion dependence of k(t) can be predicte d without extensive numerical calculations. The method may also be used to determine polymerization conditions under which simpler models of k(t) (whi ch neglect effects arising from the dependence of k(t) on chain length) may be applied. Calculations for methyl methacrylate, styrene, and butyl acryl ate bulk polymerizations up to high degrees of monomer conversion show that the impact of chain length on termination varies with conversion and stron gly depends on the type of monomer.