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Ab Initio Study of Free‐Radical Polymerization: Polyethylene Propagation Kinetics
Author(s) -
Van Cauter Karen,
Van Speybroeck Veronique,
Vansteenkiste Peter,
Reyniers MarieFrancoise,
Waroquier Michel
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200500249
Subject(s) - kinetics , polyethylene , polymerization , ab initio , radical polymerization , chemistry , materials science , computational chemistry , polymer chemistry , photochemistry , polymer , organic chemistry , physics , classical mechanics
The chain‐length dependence of the propagation rate coefficient for the free‐radical polymerization of ethylene was investigated on an ab initio basis. Polyethylene was chosen as a test system because of its structural simplicity. Ab initio density functional theory at the B3LYP/6‐31g(d) level was applied to study the kinetics of a set of addition reactions of a systematically growing radical alkyl chain to ethylene. These reactions are propagation steps in the free‐radical polymerization of ethylene. Special attention was paid to low normal modes corresponding to internal rotations (IR), since the latter are important for an accurate description of the partition functions. The effect of coupling of the IR modes is also discussed. A comparison is made with the propagation rate constant derived from experiment. The results indicate that the propagation rate coefficient has largely converged by the hexyl radical stage, though a weaker chain‐length dependence of k p for longer chains was detected.