TEMPLATE POLYMERIZATION OF N-VINYLIMIDAZOLE ALONG POLY(METHACRYLIC ACID) IN WATER .5. INFLUENCE OF TEMPLATE TACTICITY

The template polymerization of N-vinylimidazole in water along isotactic and syndiotactic poly(methacrylic acid) (PMAA) of various molecular weights was studied. The polymerization could be described with the same mechanism as developed for conventional PMAA. The maximum enhancement in the rate of polymerization followed the order isotactic < syndiotactic < conventional PMAA. This was explained by a lower template-radical interaction for isotactic PMAA and by a lower rate of radical propagation along syndiotactic PMAA with respect to conventional PMAA. Both effects were corroborated by different dependencies of the rate of polymerization and molecular weights of the formed poly(N-vinylimidazole) (PVIm) on the template molecular weight. The tacticity of the formed PVIm was different from PVIm synthesized in the absence of the template. The isotactic triad content was somewhat enhanced irrespective of template tacticity when high template molecular weights were used. Although radicals grow in close proximity to the template, Bernouillian statistics were obeyed except when comparatively short template chains were employed, in which case the most stereoregular PVIm was obtained. Independent of template tacticity, a partial suppression of anhydride formation at elevated temperatures was found in the case of template-formed complexes. This was ascribed to an enhanced interaction in the complex as compared to synthetic complexes.