Abstract
The elucidation of the mechanism of inhibition and retardation of polymerization reactions of quinones has been investigated using the charge-transfer complexes of N,N-dimethylaniline (DMA) and triphenylphosphine (TPP) with chloranil as inhibitors for the bulk and solution polymerizations of vinyl acetate (VA) in benzene and in acetonitrile. The complexes have proved to be very efficient inhibitors. The efficiency of inhibition was found to depend on the stability of the complexes, the nature of the electron donor, and its ratio relative to chloranil, as well as on the polarity of the solvent. The greater efficiency (1) in the polar solvent and (2) of the complexes of TPP compared with that of the amine support the idea that inhibition reactions involve electron transfer from the growing radicals to the quinone, with the formation of molecular complexes of macrocations and semiquinone anions. The latter are the actual inhibiting species, so that the inhibiting efficiency is determined by the feasibility of their formation in the polymerizing system. The nature of the inhibition products depends on the extent to which the semiquinones are found as kinetically independent species in the medium. The inhibition reactions should accordingly be considered as oxidation—reduction processes in which the growing chains are the electron donors.
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Yassin, A., Rizk, N. The Charge-Transfer Complexes as Polymerization Inhibitors. IV. Studies of the Mechanism of Inhibition of Vinyl Acetate Polymerization Using N,N-Dimethylaniline and Triphenylphosphine—Chloranil Complexes. Polym J 10, 77–85 (1978). https://doi.org/10.1295/polymj.10.77
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DOI: https://doi.org/10.1295/polymj.10.77