Simultaneous Deconvolution of MWD and CCD of Ethylene/1‐Olefin Copolymers Using Genetic Algorithm

Abstract

Summary Multiple‐site‐type catalytic systems produce ethylene/1‐olefin copolymers with broad molecular weight distribution (MWD) and chemical composition distribution (CCD) because each active site type produces chains with distinct chain microstructures. Simultaneous deconvolution of the MWD and CCD can be used to identify the number of active site types and chain microstructures produced on each active site type by performing parameter estimation to minimize the sum of the squares of differences between experimental and model data. However, conventional optimization algorithms often rely on the adequate initial guess. In this work, a genetic algorithm, which is a stochastic optimization search heuristic that mimics the natural evolution process, was implemented during the simultaneous deconvolution. The proposed approach was validated with simulated data of model ethylene/1‐butene copolymers produced using a system with three active site types.

The interrelationships between microstructure and melting, crystallization and thermal degradation behaviors of fractionated ethylene/1-butene copolymer

“…2) with the best regression factor. The multi-subcurves can be attributed to the different active sites of Z-N catalyst, as multiple-site-type catalytic systems produce ethylene/α-olefin copolymers with broad MWD and chemical composition distribution (CCD) due to each active site produces chains with distinct chain microstructures [39]. As shown in Figs.…”

Identification of Site Types for Ethylene/1‐Olefin Copolymerization in Two‐Reactor System Using Simultaneous Deconvolution of Molecular Weight and Chemical Composition Distribution

“…Deconvolution is a technique that can be used to help identify a number of site types and chain microstructures of polymers produced on each site type from overall microstructural distributions. [ 9–19 ] Previous works have investigated deconvolution of MWD obtained from gel permeation chromatography [ 20–25 ] and deconvolution of CCD obtained from temperature rising elution fractionation, [ 26–30 ] crystallization analysis fractionation, [ 31,32 ] or crystallization elution fractionation. [ 33 ] Recently, several simultaneous deconvolution strategies have been developed to avoid the inconsistency on a number of site types estimated from deconvolution of the same sample with different microstructural information.…”

“…[ 33 ] Recently, several simultaneous deconvolution strategies have been developed to avoid the inconsistency on a number of site types estimated from deconvolution of the same sample with different microstructural information. [ 10–14 ] However, applications of these techniques are still limited to products from a simple single reactor system.…”

Application of Genetic Algorithm in Simultaneous Deconvolution: Case Studies of Ethylene/1‐Butene Copolymers with Direct and Inverse MW/CC Relationships

“…Deconvolution is a technique developed to help identify a number of site types for multiple‐site‐type catalytic systems (e.g., system with multiple‐site‐type catalysts, mixed or hybrid catalytic system, or multi‐reactor system). [ 1–9 ] From the deconvolution analysis, mass fraction and chain microstructures of polymers produced on each site type can also be estimated. This information is important for understanding the behavior of site types and how polymerization conditions affect chain microstructures of polymers produced on each site type, which allows us to tailor make polymers with desired chain microstructures and properties.…”

“…Simultaneous deconvolution of MWD and CCD have also been proposed to help avoid possible discrepancies on a number of site types and model parameters when deconvolution of MWD and CCD of the same sample are considered separately. [ 3–5 ]…”