Ionic Liquids as Advantageous Reaction Media for Free Radical Polymerization

Abstract

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.

Photoiniferter RAFT Accelerated by Ionic Liquids in Organic Solvent Systems

“…The hydrophobic ILs with [TFSI] and [PF 6 ] anions demonstrated good solubility for PMMA as expected, achieving 90% conversion within 3 h. The high reaction rate is similar to the effect that ILs have had as media for free-radical polymerizations, which is well-known but not fully understood due to the complexity of the multicomponent IL as a solvent . While some correlation between polarity and reaction kinetics exists due to the lowering of activation energy by stabilization of the radical, viscosity appears to impact this relationship in our results; higher values reduce bimolecular termination between growing chains . Thurecht has gone further, theorizing the existence of a “protected radical” whereby a monomer domain protected the propagating chain end, providing bulk-polymerization reaction conditions .…”

“…47 While some correlation between polarity and reaction kinetics exists due to the lowering of activation energy by stabilization of the radical, 48 viscosity appears to impact this relationship in our results; 32 higher values reduce bimolecular termination between growing chains. 29 Thurecht has gone further, theorizing the existence of a "protected radical" whereby a monomer domain protected the propagating chain end, providing bulk-polymerization reaction conditions. 30 This also explains, as happens in our reactions at high conversions, the continued high reaction rates after the solidification of the reaction medium into a gel.…”

Extremely Soft, Conductive, and Transparent Ionic Gels by 3D Optical Printing

“…Despite the fact that polymers are considered the best matrix to immobilize ILs, only a few polymer–IL combinations are used till now . Several researches have reported IL‐immobilized stable polymer gels and, among them, methacrylate and styrene‐based polymers have been extensively studied . Also, compatibility of IL with polymer is also a major issue in developing IL‐mediated gel polymers.…”

“…[21][22][23] Several researches have reported IL-immobilized stable polymer gels and, among them, methacrylate and styrene-based polymers have been extensively studied. [3,[21][22][23][24] Also, compatibility of IL with polymer is also a major issue in developing IL-mediated gel polymers. The versatility of both IL and polymer chemistry allows us to develop a new combination utilizing the advantageous thiol-ene reaction and incorporating IL.…”

Synthesis of traditional and ionic polymethacrylates by anion catalyzed group transfer polymerization

“…Furthermore, precipitation of the polymer was observed in the course of the polymerization in all examples. Moreover, the broad molecular weight distribution obtained was not surprising using an ionic liquid as solvent for polymerization because high polydispersity was also observed in case of radical polymerization in ionic liquids . A domain structure of ionic liquids may be one reason for this effect .…”