A Modified Dynamic Model to Estimate the Reactivity Ratios of Ethylene/1-Olefin Copolymers

Polymerization kinetic models play a pivotal role in the prediction of copolymer microstructures and polymerization rates, but estimating reactivity ratios still poses challenges for olefin coordination polymerization. The conventional estimation approach uses data collected from low-conversion batch or semibatch copolymerizations across a relatively narrow range of initial monomer/comonomer ratios, with the reactivity ratios being estimated fitting the Mayo-Lewis equation to the experimental data. However, if significant composition drift is significant, one must use a dynamic model to estimate the reactivity ratios. The hard-to-avoid comonomer composition drift is considered a foe of reactivity ratio estimation methods and thus avoided at all costs. In this article, we propose a dynamic mathematical model to estimate reactivity ratios for ethylene/1-olefin copolymerizations in semibatch reactors under substantial composition drift, thus turning a foe into a friend. We applied our estimation method to ethylene/1-hexene copolymerizations using a constrained geometry catalyst. The results underscore how our approach can successfully estimate reactivity ratios of ethylene/1-olefin copolymerizations, considering comonomer composition drift.