Analysis of Ethylene/1-Olefin Copolymers Made with Ziegler-Natta Catalysts by Deconvolution of Molecular Weight and Average Short Chain Branching Distributions

In this article a systematic method is proposed to deconvolute the time-dependent molecular weight distributions (MWD) and average comonomer fraction profiles of ethylene/1-olefin copolymers made with heterogeneous Ziegler-Natta catalysts. These distributions with a high-temperature gel permeation chromatography equipped with an infrared detector at four different polymerization times have been measured and used this information to infer how the fractions of polymer made on each site type varied with polymerization time. The model estimates here the minimum number of active site types needed to describe these copolymers, the MWD of polymer populations made on each site type, and their average comonomer fractions. This method is useful to quantify the microstructure of olefin copolymers made with multiple site type catalysts using the least number of adjustable parameters.