Photochemical synthesis and formation mechanisms of polyvinyl acetate–CoIII(salen) “dormant” chains during “living” radical polymerization
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The formation of “dormant” chains due to the acceptance of the photodissociation products of vinyl acetate by stable CoII(salen) radicals was studied. The rate of formation of “dormant” chains was found experimentally to be considerably higher than that of initiating radicals upon the initiator-free photopolymerization of vinyl acetate. A high rate of formation of “dormant” chains is caused by supression of the cell effect in the presence of a strong inhibitor. A kinetic scheme was proposed which allowed drawing up a mechanism of formation of “dormant” chains as a mathematical model suitable for the quantitative description of the process. The comparison between the absorption spectra of the reaction system at different reaction steps and the quantum chemically calculated spectra of forming “dormant” chains showed the polymer chain initiation to afford the acyl radical. The constants for the growing radicals–CoII(salen) interaction, the quantum yield of the Co–C bond dissociation in “dormant” chains, and the quantum yield of the initiator-free vinyl acetate photopolymerization were determined.
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