Mechanism of Propylene Oxide Polymerization Promoted by N-Heterocyclic Olefins

Miasser Alghamdi, Luigi Cavallo, Laura Falivene

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We report a mechanistic DFT investigation of the organopolymerization of propylene oxide (PO) promoted by N-heterocyclic olefins (NHOs) in combination with benzylic alcohol (BnOH). Calculations support the experimentally based hypothesis of two competing pathways, namely, the anionic and zwitterionic pathways. The former is based on an acid–base cooperativity between BnOH and the NHO, promoting ring opening of PO by BnO–. The latter occurs through the formation of a zwitterionic adduct by nucleophilic attack of the exocyclic carbon atom of the NHO on the PO, with the concerted ring opening of PO. The two initiating species cannot interconvert, and chain elongation can proceed from both initiation adducts. Potential energy surfaces were computed for a set of NHOs to clarify the effects of the steric and electronic properties of the NHO on the system reactivity. The results achieved represent useful insight toward the synthesis of PPO with better properties with respect to the polymer obtained with the experimental tested systems because the computationally proposed NHO system is the only one that favors the mechanism leading to higher molecular weight.
Original languageEnglish (US)
Pages (from-to)2730-2737
Number of pages8
JournalThe Journal of Physical Chemistry C
Issue number5
StatePublished - Jan 25 2017

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by funding from King Abdullah University of Science and Technology (KAUST).


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