A Consideration on Propagation Mechanism of Radical Polymerization -Influence of N, N-Dimethylaniline on the Hyperconjugation Effect in Radical Polymerization of Methylated Styrenes-

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Other Title
  • ラジカル重合の生長反応の機構の一考察 ―メチルスチレンのラジカル重合における超共役効果に対する N,N-ジメチルアニリンの作用―
  • ビニル重合　ＣＣＣＸＶＩＩＩ　　ラジカル重合の生長反応の機構の一考察　　メチルスチレンのラジカル重合における超共役効果に対するＮ，Ｎ′‐ジメチルアニリンの作用

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The polymerization of methylated styrenes initiated by AIBN was carried out in benzene in absence and presence of N, N-dimethylaniline (DMA). In the case of p-methyl-, p-ethyl-, 3, 4-dimethyl- or 2, 4-dimethyl-styrenes, the rate of polymerization (Rp) increased and then, after passing a maximum, decreased, with increasing concentration of DMA. On the other hand, Rp of styrene, m-methyl-, p-t-butyl- or 2, 5-dimethyl-styrenes was independent of the presence or absence of DMA. These phenomena could be explained by considering that the hyperconjugation effect of methyl group of styrenes was stimulated by DMA. In order to investigate the exact mechanism of the stimulation, the propagation reaction of the vinyl polymerization via radical mechanism was discussed.<BR>As a principal transitional complex in the propagation step of radical polymerization, (3a) was considered.<BR><BR>This consideration was found to be supported by the linear relationship between activation energy of the propagation step (Ep) and easiness of transfer of electron from radical end to monomer, which was expressed by [Ea(M)-Ip(R)], where Ea(M) is electron affinity of monomer and Ip(R) is ionization potential of radical. Ea(M) and Ip(R) were calculated by SHMO method.<BR>Granting that (3a) is a transitional complex, the effect of DMA on the rate of polymerization of methylated styrenes could be explained well.

Journal

  • NIPPON KAGAKU KAISHI

    NIPPON KAGAKU KAISHI 1975 (1), 177-183, 1975-01-10

    The Chemical Society of Japan

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