The mechanism of the self-initiated thermal polymerization of styrene. Theoretical solution of a classic problem
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Updated: Jul 7, 2026

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
Kelli S Khuong1, Walter H Jones, William A Pryor
1Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
Abstract:
The Mayo and Flory mechanisms for the self-initiation of styrene polymerization were explored with B3LYP and BPW91 density functional calculations. The Diels-Alder dimer (AH) is the key intermediate, and the lowest energy pathway for AH formation is a stepwise mechanism via a gauche/sickle (*M2*Gs) or gauche/U-shaped (*M2*Gu) diradical. Ring closure of the 1,4-diradical to diphenylcyclobutane (DCB) is predicted to have a lower barrier than ring closure to AH. Dynamic effects are likely to play an important role in determining the rate of AH versus DCB formation. Hydrogen transfer from AH to styrene to generate two monoradical species is predicted to be a reasonable process that initiates monoradical polymerization.
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