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Effects of carbonyl compounds [acetone, acetophenone, and benzaldehydes (p‐MeO, p‐NO2, and unsubstituted)] were investigated in the polymerization of isobutyl vinyl ether (IBVE) by trimethylsilyl halide/zinc halide (Me3SiX/ZnX2; X = I, Br, Cl) initiating systems in toluene at −15°C. In the presence of acetone and the three benzaldehydes, Me3Sil/Znl2 induced living cationic polymerization, where the number‐average molecular weights (M̄n) of the polymers increased proportionally to monomer conversion and agreed with the calculated values on the assumption that one living polymer per molecule of Me3SiI is formed. The molecular weight distributions (MWDs) stayed very narrow (M̄w/M̄n ≤ 1,1) throughout the reaction. With acetophenone, the M̄n values were larger than the calculated values and the MWDs were slightly broader. For less reactive silyl halides, Me3SiBr and Me3SiCl, p‐MeO‐benzaldehyde gave better results in terms of M̄n values and MWDs than unsubstituted benzaldehyde. 1H NMR analysis of the polymer end structure and the products of model reactions has shown that the initiation occurs via a silyloxycarbocation (Me3SiOC+R1R2 · X−) that is generated by a reaction of Me3SiX with carbonyl compounds.
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Kamigaito et al. (1993) studied this question.
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