Polymerization of N-Butyl Vinyl Ether Catalyzed by Iron-Containing Imidazolium-Based Ionic Liquid

The iron-containing imidazolium-based ionic liquids (ILs) 1-n-butyl-3-methylimidazolium heptachlorodiferrate (BMI.Fe₂Cl₇) and 1-n-butyl-3-methylimidazolium tetrachloroferrate (BMI.FeCl₄) are applied as catalysts in the homogeneous polymerization of n-butyl vinyl ether. Both solventless conditions as well as using different organic solvents, catalyst concentrations, temperatures, and reaction times are tested to assess the polymerization conditions that lead to the highest molecular weights of poly(n-butyl vinyl ether). The Lewis acidic IL BMI.Fe₂Cl₇ proves to be highly efficient, even at low catalyst concentrations. In bulk polymerization, polymers with 142 kg mol⁻¹ are obtained using a 1:10000 molar ratio of catalyst to monomer. In solution polymerization, the monomer consumption is also rapid and the molecular weight of the polymer is related to the catalyst concentration used. These results indicate the potential of this catalyst for industrial applications. In contrast with the acidic IL, the neutral iron-containing imidazolium-based IL BMI.FeCl₄ does not show any catalytic activity.