A Modified\nDynamic Model to Estimate the Reactivity\nRatios of Ethylene/1-Olefin Copolymers

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