Effect of bulkiness and lewis acidity of aluminium compounds on the anionic polymerization of methyl methacrylate in toluene

Abstract

AbstractThe bulkiness and the Lewis acidity of added aluminium compounds strongly affect the polymerization of methyl methacrylate in toluene at −78°C. The polymerization strongly deviates from ‘ideal’ first‐order kinetics, i.e. the first‐order time‐conversion plots are kinked at low monomer conversions. Additionally, for the more bulky and more Lewis‐acid aluminium alkyls, the time‐conversion plots show a further downward curvature. This curvature is not the result of a termination reaction because the polymers are free of side products like β‐ketoesters or vinyl ketone units. The molecular weight distributions and tacticities of the resulting polymers are also affected. Dependent on the aluminium compound used, molecular weight distributions are in the range of 1.2 < Mw/Mn < 7, and the triad tacticity of the polymer can change from highly syndiotactic over atactic or heterotactic to highly isotactic.