Influence of imidazolium-based ionic liquids on the synthesis of amphiphilic copolymers based on n-butylmethacrylate and a zwitterionic methacrylate†

Imidazolium-based ionic liquids are used as new solvents for the synthesis of statistical copolymers from methacrylates of strongly differing polarities and solubilities, namely of n-butylmethacrylate and 3-(N-2-[methacryloyloxyethyl]-N,N dimethyl-3-ammonio)propane sulfonate. Though difficult to prepare in classical solvents, true copolymers of these monomers can be obtained in ionic liquids, providing zwitterionic amphiphilic polymers. The relative reactivity of the monomers and thus the copolymer composition is influenced by the ionic liquid used. Analysis of the copolymers using 1H NMR spectroscopy, elemental analysis, and asymmetrical flow field-flow fractionation (AF4) shows the influence of both the length of the alkyl chain bound at the nitrogen atom of the imidazolium ring and the anion of the ionic liquid on the structure of the copolymers. Furthermore, the highly polar methacrylate with a sulfobetaine moiety is only slightly preferred in copolymerization if ionic liquids are used as solvents for copolymerization. The ratio of monomer segments in the copolymer can be influenced by the selection of the ionic liquid used as a solvent for polymer synthesis and by the variation of the monomer ratio selected for copolymerization if it is carried out in an ionic liquid. This opens new possibilities for a broad variation of amphiphilic copolymer structures obtained through free radical copolymerization of differently polar monomers. Copyright © 2008 John Wiley & Sons, Ltd.