Ionic Liquids as Advantageous Reaction Media for Free Radical Polymerization

Ionic liquids are attractive solvents for polymer synthesis because their properties can be easily and broadly tuned by varying the structure of both the cation and the anion. Application of ionic liquids as reaction medium for free radical polymerization of vinyl monomers, such as methacrylates or styrene, results in high yields and high molecular weights of the polymers. Reasons for these effects are only partially due to the high viscosity of ionic liquids, which may reduce bimolecular termination of the propagating chains, but are also due to solvent cage effects that differ from those in traditional organic solvents because of strong ionic interactions between the individual ions of the ionic liquids. Furthermore, the high dissolving power of ionic liquids for both weakly polar as well as highly polar monomers makes ionic liquids interesting as solvents for statistical copolymerization. Interestingly, variation of the alkyl chain length of substituents at the cation of the ionic liquid allows altering of copolymer composition.