NMR studies on the stereospecific polymerization of methyl vinyl ether. Part I. Polymerization by metal halides: Penultimate effect

Methyl vinyl ether (MVE) was polymerized under various conditions by BF 3 ·O(C 2 H 5 ) 2 and SnCl 4 ·CCl 3 CO 2 H catalysts. The effect of polymerization conditions on the steric structure of poly(methyl vinyl ether) (PMVE) was studied by NMR spectra. It was found that the triad isotacticity of PMVE decreased and the syndiotacticity and heterotacticity increased with increasing polarity of the solvent and increasing polymerization temperature. This result coincided with the qualitative conclusion estimated from softening point and infrared spectra. However, the variation of tacticity by the change of the polarity of a solvent was not so large as expected. There was no large difference between the behavior of BF 3 ·O(C 2 H 5 ) 2 and SnCl 4 ·CCl 3 CO 2 H as catalysts. From the relation between the difference of free energy of monomer addition due to the steric structure of the polymer and the polymerization temperature, it was concluded that the penultimate effect really existed and was due to only the difference in enthalpy in the MVE–BF 3 . O(C 2 H 5 ) 2 or MVE–SnCl 4 ·CCl 3 CO 2 H systems. The penultimate effect was not greatly changed by the polymerization conditions in these systems.