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PPV Polymerization through the Gilch Route: Diradical Character of Monomers
Author(s) -
Nikolić Jelena D.,
Wouters Sebastian,
Romanova Julia,
Shimizu Akihiro,
Champagne Benoît,
Junkers Tanja,
Vanderzande Dirk,
Van Neck Dimitri,
Waroquier Michel,
Van Speybroeck Veronique,
Catak Saron
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201501900
Subject(s) - diradical , polymerization , monomer , chemistry , heteroatom , photochemistry , polymer chemistry , polymer , ring (chemistry) , organic chemistry , singlet state , excited state , nuclear physics , physics
Abstract Despite various studies on the polymerization of poly( p ‐phenylene vinylene) (PPV) through different precursor routes, detailed mechanistic knowledge on the individual reaction steps and intermediates is still incomplete. The present study aims to gain more insight into the radical polymerization of PPV through the Gilch route. The initial steps of the polymerization involve the formation of a p ‐quinodimethane intermediate, which spontaneously self‐initiates through a dimerization process leading to the formation of diradical species; chain propagation ensues on both sides of the diradical or chain termination occurs by the formation of side products, such as [2.2]paracyclophanes. Furthermore, different p ‐quinodimethane systems were assessed with respect to the size of their aromatic core as well as the presence of heteroatoms in/on the conjugated system. The nature of the aromatic core and the specific substituents alter the electronic structure of the p ‐quinodimethane monomers, affecting the mechanism of polymerization. The diradical character of the monomers has been investigated with several advanced methodologies, such as spin‐projected UHF, CASSCF, CASPT2, and DMRG calculations. It was shown that larger aromatic cores led to a higher diradical character in the monomers, which in turn is proposed to cause rapid initiation.